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2023 Volume 39 Issue 11
2023, 39(11): 221201
doi: 10.3866/PKU.WHXB202212011
Abstract:
Rapid increase in energy shortage and ecological environmental pollution has become a major issue that has been continuously drawing global attention, because it severely affects human health and limits sustainable social development. Various technologies have been developed and used to rationalize the utilization of new energy sources and pollution control. Among these technologies, photocatalysis has become a research priority in the field of environmental governance and energy development. Advantages such as low energy consumption, no secondary pollution, simple operation methods, and mild reaction conditions make photocatalysis an attractive choice. Notably, although photocatalysis is a promising approach for enhancing antibiotic removal and CO2 reduction efficiency, the industrialization and large-scale application of photocatalysts is limited because of issues such as low photo-absorption efficiency, redox capacity, and photogenerated electron separation or migration efficiency. The progress of current research on the regulation of composition/structure and performance of photocatalysts has promoted the exploration of efficient and practical modification strategies to construct photocatalyst composites with improved performance by facilitating light absorption/utilization and enhancing photocatalytic surface/interface reaction performance. Among the many common modification strategies, the construction of a Z-scheme heterojunction can enhance the light absorption ability and significantly reduce the recombination rate of photogenerated electron-hole pairs. Additionally, this strategy maintains the strong reduction/oxidation ability of photogenerated electrons/holes to facilitate the oxidation of environmental pollutants and conversion to clean energy. In this study, Z-scheme MnO2/BiOBr (MO/BiOBr) composites were effectively constructed using a mechanically assisted ball-milling process. In situ X-ray photoelectron spectroscopy under dark and light conditions confirmed that photoexcited electrons in MnO2 can migrate directionally to BiOBr through Mn3+/Mn4+ redox couple to create a Z-scheme transfer path. A similar conclusion can also be deduced from the results of electron spin-resonance spectroscopy and band structure analysis. The formation of a Z-scheme heterojunction between MnO2 and BiOBr, attributed to the Mn3+/Mn4+ redox couple from MnO2 and staggered energy band, enabled the space separation of oxidation and reduction centers. Furthermore, compared with BiOBr, MO/BiOBr composites exhibited enhanced light absorption and a markedly reduced photoinduced electron-hole pair recombination rate, as confirmed by ultraviolet-visible diffuse reflectance spectroscopy and photoluminescence spectroscopy. Thus, the MO/BiOBr composites exhibited exceptional photocatalytic performance toward ciprofloxacin (CIP) oxidation and CO evolution. The CIP removal efficiency of the MO/BiOBr composites reached 77.3% in just 60 min, which is 1.28 times higher than that of BiOBr (60.2%). Simultaneously, the photocatalytic CO2-to-CO performance of the MO/BiOBr composites (20.02 µmol·g−1·h−1) was found to be 2.20-fold higher than that of BiOBr (9.08 µmol·g−1·h−1). Photocurrent measurement and electrochemical impedance spectroscopy indicated that the MnO2/BiOBr Z-scheme heterojunction has higher interfacial electron transfer efficiency than pure MnO2 and BiOBr. Additionally, liquid chromatograph mass spectrometry and in situ Fourier transform infrared spectroscopy is conducted to study the generation of intermediates during the photocatalytic CIP removal and CO2 reduction process. The toxicity of CIP and corresponding intermediates after the photocatalytic degradation of the MO/BiOBr composites was evaluated using toxicity estimation software (T.E.S.T.) to analyze the actual physiological toxicity, based on indexes such as Daphnia Magna lethal concentration 50% (LC50, 48 h), Fathead Minnow lethal dose 50% (LD50, 96 h), mutagenicity, and bioaccumulation factor. Thus, this study proposed a novel and simplified approach for constructing a Z-scheme heterojunction to facilitate solar-derived antibiotic removal and fuel synthesis. ![]()
Rapid increase in energy shortage and ecological environmental pollution has become a major issue that has been continuously drawing global attention, because it severely affects human health and limits sustainable social development. Various technologies have been developed and used to rationalize the utilization of new energy sources and pollution control. Among these technologies, photocatalysis has become a research priority in the field of environmental governance and energy development. Advantages such as low energy consumption, no secondary pollution, simple operation methods, and mild reaction conditions make photocatalysis an attractive choice. Notably, although photocatalysis is a promising approach for enhancing antibiotic removal and CO2 reduction efficiency, the industrialization and large-scale application of photocatalysts is limited because of issues such as low photo-absorption efficiency, redox capacity, and photogenerated electron separation or migration efficiency. The progress of current research on the regulation of composition/structure and performance of photocatalysts has promoted the exploration of efficient and practical modification strategies to construct photocatalyst composites with improved performance by facilitating light absorption/utilization and enhancing photocatalytic surface/interface reaction performance. Among the many common modification strategies, the construction of a Z-scheme heterojunction can enhance the light absorption ability and significantly reduce the recombination rate of photogenerated electron-hole pairs. Additionally, this strategy maintains the strong reduction/oxidation ability of photogenerated electrons/holes to facilitate the oxidation of environmental pollutants and conversion to clean energy. In this study, Z-scheme MnO2/BiOBr (MO/BiOBr) composites were effectively constructed using a mechanically assisted ball-milling process. In situ X-ray photoelectron spectroscopy under dark and light conditions confirmed that photoexcited electrons in MnO2 can migrate directionally to BiOBr through Mn3+/Mn4+ redox couple to create a Z-scheme transfer path. A similar conclusion can also be deduced from the results of electron spin-resonance spectroscopy and band structure analysis. The formation of a Z-scheme heterojunction between MnO2 and BiOBr, attributed to the Mn3+/Mn4+ redox couple from MnO2 and staggered energy band, enabled the space separation of oxidation and reduction centers. Furthermore, compared with BiOBr, MO/BiOBr composites exhibited enhanced light absorption and a markedly reduced photoinduced electron-hole pair recombination rate, as confirmed by ultraviolet-visible diffuse reflectance spectroscopy and photoluminescence spectroscopy. Thus, the MO/BiOBr composites exhibited exceptional photocatalytic performance toward ciprofloxacin (CIP) oxidation and CO evolution. The CIP removal efficiency of the MO/BiOBr composites reached 77.3% in just 60 min, which is 1.28 times higher than that of BiOBr (60.2%). Simultaneously, the photocatalytic CO2-to-CO performance of the MO/BiOBr composites (20.02 µmol·g−1·h−1) was found to be 2.20-fold higher than that of BiOBr (9.08 µmol·g−1·h−1). Photocurrent measurement and electrochemical impedance spectroscopy indicated that the MnO2/BiOBr Z-scheme heterojunction has higher interfacial electron transfer efficiency than pure MnO2 and BiOBr. Additionally, liquid chromatograph mass spectrometry and in situ Fourier transform infrared spectroscopy is conducted to study the generation of intermediates during the photocatalytic CIP removal and CO2 reduction process. The toxicity of CIP and corresponding intermediates after the photocatalytic degradation of the MO/BiOBr composites was evaluated using toxicity estimation software (T.E.S.T.) to analyze the actual physiological toxicity, based on indexes such as Daphnia Magna lethal concentration 50% (LC50, 48 h), Fathead Minnow lethal dose 50% (LD50, 96 h), mutagenicity, and bioaccumulation factor. Thus, this study proposed a novel and simplified approach for constructing a Z-scheme heterojunction to facilitate solar-derived antibiotic removal and fuel synthesis.
2023, 39(11): 221206
doi: 10.3866/PKU.WHXB202212062
Abstract:
Photocatalytic hydrogen production is a promising strategy for utilizing inexhaustible solar energy as a source of clean energy. Graphitic carbon nitride (g-C3N4) is a widely used photocatalytic material in photocatalytic hydrogen production because of its simple preparation process, suitable band structure, and high stability. However, the low charge carrier separation efficiency and small specific surface area of pristine g-C3N4 restrict its photocatalytic activity. It has been demonstrated that the construction of intramolecular donor-acceptor (D-A) systems and ultra-thin nanosheet structures are effective strategies for enhancing the photocatalytic activity of g-C3N4. Herein, an intramolecular D-A structured g-C3N4 nanosheet photocatalyst is synthesized through the thermal copolymerization of dicyandiamide and methylene blue (MB), followed by thermal exfoliation. X-ray diffraction, Fourier transform infrared spectrometry, solid-state 13C nuclear magnetic resonance, and X-ray photoelectron spectroscopy analyses reveal that MB is successfully incorporated into the g-C3N4 framework and well retained after thermal exfoliation. The resulting D-A system induces intramolecular charge transfer from the donor units (MB segment) to the acceptor units (tri-s-triazine rings) and extends the absorption edge to approximately 500 nm. The ultra-thin nanosheet structure produced by thermal exfoliation shortens the charge transfer distance from the interior to the surface of g-C3N4 and reduces the charge transfer resistance, which increases the charge carrier separation efficiency. Furthermore, the introduction of MB generates a flaky structure during copolymerization, which promotes thermal exfoliation and results in a remarkably increased specific surface area. The transient photocurrent response, electrochemical impedance spectra, and time-resolved photoluminescence decay spectra reveal that the charge transfer and separation of g-C3N4 are further promoted by integrating the intramolecular D-A system and ultra-thin nanosheet structure. Density functional theory calculations further demonstrate that MB donates electrons to tri-s-triazine rings (electron acceptor). Moreover, the highest occupied molecular orbit of D-A structured g-C3N4 is mostly distributed around the MB segment, while the lowest unoccupied molecular orbit is distributed around tri-s-triazine rings, resulting in spatially separated photogenerated electron-hole pairs. Through integrating the intramolecular D-A system and ultra-thin nanosheet structure, the obtained photocatalyst exhibits enhanced charge carrier separation, an extended absorption edge, and enlarged specific surface area. As a consequence, the D-A structured g-C3N4 nanosheet shows a considerably improved photocatalytic hydrogen production activity (2275.6 μmol·h−1·g−1), which is 5.30, 2.60, and 1.30 times that of bulk g-C3N4, D-A structured bulk g-C3N4, and g-C3N4 nanosheet, respectively. This work offers a valuable strategy for developing D-A-modified photocatalytic materials for solar energy conversion. ![]()
Photocatalytic hydrogen production is a promising strategy for utilizing inexhaustible solar energy as a source of clean energy. Graphitic carbon nitride (g-C3N4) is a widely used photocatalytic material in photocatalytic hydrogen production because of its simple preparation process, suitable band structure, and high stability. However, the low charge carrier separation efficiency and small specific surface area of pristine g-C3N4 restrict its photocatalytic activity. It has been demonstrated that the construction of intramolecular donor-acceptor (D-A) systems and ultra-thin nanosheet structures are effective strategies for enhancing the photocatalytic activity of g-C3N4. Herein, an intramolecular D-A structured g-C3N4 nanosheet photocatalyst is synthesized through the thermal copolymerization of dicyandiamide and methylene blue (MB), followed by thermal exfoliation. X-ray diffraction, Fourier transform infrared spectrometry, solid-state 13C nuclear magnetic resonance, and X-ray photoelectron spectroscopy analyses reveal that MB is successfully incorporated into the g-C3N4 framework and well retained after thermal exfoliation. The resulting D-A system induces intramolecular charge transfer from the donor units (MB segment) to the acceptor units (tri-s-triazine rings) and extends the absorption edge to approximately 500 nm. The ultra-thin nanosheet structure produced by thermal exfoliation shortens the charge transfer distance from the interior to the surface of g-C3N4 and reduces the charge transfer resistance, which increases the charge carrier separation efficiency. Furthermore, the introduction of MB generates a flaky structure during copolymerization, which promotes thermal exfoliation and results in a remarkably increased specific surface area. The transient photocurrent response, electrochemical impedance spectra, and time-resolved photoluminescence decay spectra reveal that the charge transfer and separation of g-C3N4 are further promoted by integrating the intramolecular D-A system and ultra-thin nanosheet structure. Density functional theory calculations further demonstrate that MB donates electrons to tri-s-triazine rings (electron acceptor). Moreover, the highest occupied molecular orbit of D-A structured g-C3N4 is mostly distributed around the MB segment, while the lowest unoccupied molecular orbit is distributed around tri-s-triazine rings, resulting in spatially separated photogenerated electron-hole pairs. Through integrating the intramolecular D-A system and ultra-thin nanosheet structure, the obtained photocatalyst exhibits enhanced charge carrier separation, an extended absorption edge, and enlarged specific surface area. As a consequence, the D-A structured g-C3N4 nanosheet shows a considerably improved photocatalytic hydrogen production activity (2275.6 μmol·h−1·g−1), which is 5.30, 2.60, and 1.30 times that of bulk g-C3N4, D-A structured bulk g-C3N4, and g-C3N4 nanosheet, respectively. This work offers a valuable strategy for developing D-A-modified photocatalytic materials for solar energy conversion.
2023, 39(11): 230101
doi: 10.3866/PKU.WHXB202301018
Abstract:
CO2, as a greenhouse gas, has excessive emissions that lead to many environmental problems and is a rich and cheap C1 resource. Effective utilization and transformation of CO2 has become an important means of achieving carbon neutrality. Oxazolidinones are important intermediates in pharmaceutical chemistry that can be synthesized by carboxylation cyclization of CO2 with propargyl amines or cycloaddition of CO2 with aziridines. Owing to CO2's high stability, these reactions typically require harsh conditions, such as high temperatures or pressures. It is desirable, but challenging, to find a catalyst that can catalyze these two types of reactions under relatively mild conditions. Metal-organic frameworks (MOFs) are an emerging class of heterogeneous catalysts that with great potential in the catalytic conversion of CO2 to value-added products because of their attractive features, such as abundant metal active sites, inherent porosity, and easy functionalities. Herein, a unique three-dimensional (3D) MOF, {(CH3NH2CH3)2[Co3(BCP)2]·6H2O·4DMF}n (1) (H4BCP: 5-(2,6-bis(4-carboxyphenyl)pyridin-4-yl) isophthalic acid; DMF: N,N'-dimethylformamide), was synthesized using carboxylic acid ligands and cobalt salts via a solvothermal method. According to structural analysis, [Co3] clusters as secondary building units (SBU) are bridged by BCP4− ligands, forming an anion framework with flu topology, and dimethylamine cations act as counter ions in the pores. The framework has rectangular channels of approximately 0.4 nm × 0.9 nm along the a-axis direction, exhibiting its porous property. Infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS) characterizations proved the coordination interaction between the carboxyl groups in the ligands and the metal ions. The powder X-Ray diffraction (PXRD) test further confirmed the phase purity of the synthesized samples. PXRD and thermogravimetry (TG) analyses indicated that 1 possessed good solvent and thermal stabilities. The catalytic experiments revealed that 1 could effectively catalyze CO2 with aziridines or propargyl amines to prepare oxazolidinones. In the cycloaddition of CO2 with aziridines, 1 can facilitate the reaction under relatively mild conditions compared to other reported MOF-based catalysts. It shows excellent universality for substrates with various substitutions on the N atom or benzene ring. Investigation of the mechanism indicated that the coordination interaction of cobalt metal sites with the nitrogen atoms of aziridines can activate the substrates. For the carboxylative cyclization of CO2 with propargylic amines, this catalyst also has a broad substrate scope. Control experiments and nuclear magnetic resonance (NMR) tests suggest that Lewis acid metal sites are responsible for the high catalytic efficiency achieved by activating the alkyne groups. Moreover, 1 showed good reusability in both reactions. Compound 1 represents a new catalyst that enables "two birds with one stone" in the catalytic synthesis of oxazolidinones using CO2. ![]()
CO2, as a greenhouse gas, has excessive emissions that lead to many environmental problems and is a rich and cheap C1 resource. Effective utilization and transformation of CO2 has become an important means of achieving carbon neutrality. Oxazolidinones are important intermediates in pharmaceutical chemistry that can be synthesized by carboxylation cyclization of CO2 with propargyl amines or cycloaddition of CO2 with aziridines. Owing to CO2's high stability, these reactions typically require harsh conditions, such as high temperatures or pressures. It is desirable, but challenging, to find a catalyst that can catalyze these two types of reactions under relatively mild conditions. Metal-organic frameworks (MOFs) are an emerging class of heterogeneous catalysts that with great potential in the catalytic conversion of CO2 to value-added products because of their attractive features, such as abundant metal active sites, inherent porosity, and easy functionalities. Herein, a unique three-dimensional (3D) MOF, {(CH3NH2CH3)2[Co3(BCP)2]·6H2O·4DMF}n (1) (H4BCP: 5-(2,6-bis(4-carboxyphenyl)pyridin-4-yl) isophthalic acid; DMF: N,N'-dimethylformamide), was synthesized using carboxylic acid ligands and cobalt salts via a solvothermal method. According to structural analysis, [Co3] clusters as secondary building units (SBU) are bridged by BCP4− ligands, forming an anion framework with flu topology, and dimethylamine cations act as counter ions in the pores. The framework has rectangular channels of approximately 0.4 nm × 0.9 nm along the a-axis direction, exhibiting its porous property. Infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS) characterizations proved the coordination interaction between the carboxyl groups in the ligands and the metal ions. The powder X-Ray diffraction (PXRD) test further confirmed the phase purity of the synthesized samples. PXRD and thermogravimetry (TG) analyses indicated that 1 possessed good solvent and thermal stabilities. The catalytic experiments revealed that 1 could effectively catalyze CO2 with aziridines or propargyl amines to prepare oxazolidinones. In the cycloaddition of CO2 with aziridines, 1 can facilitate the reaction under relatively mild conditions compared to other reported MOF-based catalysts. It shows excellent universality for substrates with various substitutions on the N atom or benzene ring. Investigation of the mechanism indicated that the coordination interaction of cobalt metal sites with the nitrogen atoms of aziridines can activate the substrates. For the carboxylative cyclization of CO2 with propargylic amines, this catalyst also has a broad substrate scope. Control experiments and nuclear magnetic resonance (NMR) tests suggest that Lewis acid metal sites are responsible for the high catalytic efficiency achieved by activating the alkyne groups. Moreover, 1 showed good reusability in both reactions. Compound 1 represents a new catalyst that enables "two birds with one stone" in the catalytic synthesis of oxazolidinones using CO2.
2023, 39(11): 230201
doi: 10.3866/PKU.WHXB202302017
Abstract:
With the exhaustion of fossil energy, the energy crisis is becoming increasingly serious, which greatly hinders the sustainable development of society. Therefore, the development of new energy technologies as a substitute for non-renewable and highly polluting fossil energy is extremely urgent. The environmental benefits and high energy density of hydrogen (H2) make it an ideal clean energy source. Photocatalytic water splitting, which was first demonstrated in the pioneering work on TiO2 photoelectrodes under UV-light irradiation, has been extensively researched and has been shown to be an effective method for addressing the global energy crisis. However, most of the photocatalysts used for H2 production still suffer from low solar energy utilization and fast photogenerated charge recombination, which seriously limit their practical applications in the field of solar-to-hydrogen energy conversion. Therefore, it is necessary yet greatly challenging to develop a visible-light-responsive photocatalyst with efficient photogenerated charge separation through reasonable modification strategy. Layered structured ZnIn2S4 (ZIS) is a promising photocatalyst to split water for H2 evolution owing to its suitable electronic structure, strong light absorption, chemical stability, and low toxicity. However, its low charge separation efficiency renders its photocatalytic performance unsatisfactory. Herein, to overcome this issue, a band structure regulation strategy that integrates solid solution formation with heterostructure construction was proposed. By growing ZnxCd1−xIn2S4 (ZCIS) nanosheets on the surface of CeO2 hollow spheres in situ, a novel hollow heterostructure CeO2/ZCIS with efficient charge separation was constructed as photocatalyst for H2 generation. The introduction of the Cd cation in ZIS upshifts the conduction band (CB) and valence band (VB) of ZCIS, enhancing the built-in electrical field on the interface. Those electronic band changes induce the S-scheme structure in CeO2/ZCIS, promoting charge separation for photocatalysis. Moreover, the upshift of the CB generates photoelectrons with high H2 generation ability. As a result, the optimal 1:6-CeO2/Zn0.9Cd0.1In2S4 heterostructure exhibits 4.09 mmol·g−1·h−1 H2 generation during photocatalysis, which is 6.8-, 3.0-, and 2.2-fold as those of ZIS, ZCIS, and CeO2/ZIS, respectively. This work provides one efficient strategy to develop highly active S-scheme photocatalysts for hydrogen generation. ![]()
With the exhaustion of fossil energy, the energy crisis is becoming increasingly serious, which greatly hinders the sustainable development of society. Therefore, the development of new energy technologies as a substitute for non-renewable and highly polluting fossil energy is extremely urgent. The environmental benefits and high energy density of hydrogen (H2) make it an ideal clean energy source. Photocatalytic water splitting, which was first demonstrated in the pioneering work on TiO2 photoelectrodes under UV-light irradiation, has been extensively researched and has been shown to be an effective method for addressing the global energy crisis. However, most of the photocatalysts used for H2 production still suffer from low solar energy utilization and fast photogenerated charge recombination, which seriously limit their practical applications in the field of solar-to-hydrogen energy conversion. Therefore, it is necessary yet greatly challenging to develop a visible-light-responsive photocatalyst with efficient photogenerated charge separation through reasonable modification strategy. Layered structured ZnIn2S4 (ZIS) is a promising photocatalyst to split water for H2 evolution owing to its suitable electronic structure, strong light absorption, chemical stability, and low toxicity. However, its low charge separation efficiency renders its photocatalytic performance unsatisfactory. Herein, to overcome this issue, a band structure regulation strategy that integrates solid solution formation with heterostructure construction was proposed. By growing ZnxCd1−xIn2S4 (ZCIS) nanosheets on the surface of CeO2 hollow spheres in situ, a novel hollow heterostructure CeO2/ZCIS with efficient charge separation was constructed as photocatalyst for H2 generation. The introduction of the Cd cation in ZIS upshifts the conduction band (CB) and valence band (VB) of ZCIS, enhancing the built-in electrical field on the interface. Those electronic band changes induce the S-scheme structure in CeO2/ZCIS, promoting charge separation for photocatalysis. Moreover, the upshift of the CB generates photoelectrons with high H2 generation ability. As a result, the optimal 1:6-CeO2/Zn0.9Cd0.1In2S4 heterostructure exhibits 4.09 mmol·g−1·h−1 H2 generation during photocatalysis, which is 6.8-, 3.0-, and 2.2-fold as those of ZIS, ZCIS, and CeO2/ZIS, respectively. This work provides one efficient strategy to develop highly active S-scheme photocatalysts for hydrogen generation.
2023, 39(11): 230202
doi: 10.3866/PKU.WHXB202302021
Abstract:
The conversion of CO2 into CO via the reverse water gas shift (RWGS) reaction has recently attracted considerable attention owing to the increase in atmospheric CO2 emissions. However, metal-supported catalysts easily undergo sintering and become inactive at high temperatures. To fabricate highly active and stable catalysts, molybdenum carbide (MoxC), with properties similar to those of precious metals, has been extensively investigated. In particular, it has been demonstrated that face-centered cubic α-MoC can strongly interact with support metals, rendering it an attractive candidate as a catalyst for the RWGS reaction. Furthermore, it has been previously demonstrated that metallic Ir, with unique electronic properties and a low CO desorption barrier, is active for the RWGS at low temperatures (250–300 ℃). Accordingly, in this study, a system of Ir species and α-MoC was constructed using a solvent evaporation self-assembly method. The catalytic performance of the Ir/MoC catalysts for the RWGS reaction was considerably superior to that of pure α-MoC over a wide temperature range (200–500 ℃) owing to the synergistic effect of Ir and α-MoC. The optimal 0.5%Ir/MoC catalyst yielded a CO2 conversion of 48.4% at 500 ℃, 0.1 MPa, and 300000 mL·g−1·h−1, which was comparable to the equilibrium conversion (49.9%). The CO selectivity and space-time yield of CO over 0.5%Ir/MoC reached 94.0% and 423.1 μmol·g−1·s−1, respectively, which were higher than most of the previously reported values. Moreover, 0.5%Ir/MoC retained its catalytic properties over 100 h and demonstrated excellent stability at high temperatures. Several characterization methods were used to demonstrate that the Ir species supported on α-MoC substrates were highly dispersed. The strong metal-support interaction between Ir and α-MoC, which occurred via electron transfer, considerably improved the stability of the Ir/MoC catalysts. For the Ir/MoC catalysts with Ir loadings > 0.2% (mass fraction), Ir single atoms (Ir1) and clusters (Irn) coexisted to create Irn-Ir1-C-Mo synergistic sites between Ir and α-MoC. The number of Ir1 species and size of Irn species of 0.5%Ir/MoC were higher and smaller, respectively, than those of the other Ir/MoC catalysts. This conferred 0.5%Ir/MoC an optimal electron density, which contributed to the remarkable adsorption and activation of CO2 and H2 during the RWGS. In situ diffuse reflectance infrared Fourier transform spectroscopy experiments revealed that the RWGS reaction mechanism occurred via a formate pathway. Although the formation of Irn-Ir1-C-Mo synergistic sites did not affect the reaction mechanism, the generation and decomposition of formate intermediates were distinctly promoted. Therefore, the catalytic performance of Ir/MoC was effectively improved by the synergistic effect. This study provides a guide for designing efficient and stable catalysts for CO2 utilization.![]()
The conversion of CO2 into CO via the reverse water gas shift (RWGS) reaction has recently attracted considerable attention owing to the increase in atmospheric CO2 emissions. However, metal-supported catalysts easily undergo sintering and become inactive at high temperatures. To fabricate highly active and stable catalysts, molybdenum carbide (MoxC), with properties similar to those of precious metals, has been extensively investigated. In particular, it has been demonstrated that face-centered cubic α-MoC can strongly interact with support metals, rendering it an attractive candidate as a catalyst for the RWGS reaction. Furthermore, it has been previously demonstrated that metallic Ir, with unique electronic properties and a low CO desorption barrier, is active for the RWGS at low temperatures (250–300 ℃). Accordingly, in this study, a system of Ir species and α-MoC was constructed using a solvent evaporation self-assembly method. The catalytic performance of the Ir/MoC catalysts for the RWGS reaction was considerably superior to that of pure α-MoC over a wide temperature range (200–500 ℃) owing to the synergistic effect of Ir and α-MoC. The optimal 0.5%Ir/MoC catalyst yielded a CO2 conversion of 48.4% at 500 ℃, 0.1 MPa, and 300000 mL·g−1·h−1, which was comparable to the equilibrium conversion (49.9%). The CO selectivity and space-time yield of CO over 0.5%Ir/MoC reached 94.0% and 423.1 μmol·g−1·s−1, respectively, which were higher than most of the previously reported values. Moreover, 0.5%Ir/MoC retained its catalytic properties over 100 h and demonstrated excellent stability at high temperatures. Several characterization methods were used to demonstrate that the Ir species supported on α-MoC substrates were highly dispersed. The strong metal-support interaction between Ir and α-MoC, which occurred via electron transfer, considerably improved the stability of the Ir/MoC catalysts. For the Ir/MoC catalysts with Ir loadings > 0.2% (mass fraction), Ir single atoms (Ir1) and clusters (Irn) coexisted to create Irn-Ir1-C-Mo synergistic sites between Ir and α-MoC. The number of Ir1 species and size of Irn species of 0.5%Ir/MoC were higher and smaller, respectively, than those of the other Ir/MoC catalysts. This conferred 0.5%Ir/MoC an optimal electron density, which contributed to the remarkable adsorption and activation of CO2 and H2 during the RWGS. In situ diffuse reflectance infrared Fourier transform spectroscopy experiments revealed that the RWGS reaction mechanism occurred via a formate pathway. Although the formation of Irn-Ir1-C-Mo synergistic sites did not affect the reaction mechanism, the generation and decomposition of formate intermediates were distinctly promoted. Therefore, the catalytic performance of Ir/MoC was effectively improved by the synergistic effect. This study provides a guide for designing efficient and stable catalysts for CO2 utilization.
2023, 39(11): 221202
doi: 10.3866/PKU.WHXB202212023
Abstract:
The anchor group of a molecule determines its binding characteristics with electrodes. It impacts the molecular conductance of the formed single molecule junctions and is of great importance to the field of molecular electronics. Thiophene unit is an emerging anchor ligand and shows the ability to bind with Au electrodes. As a building block in designing organic photoelectric materials, thiophene has a potential in expanding the variety of target molecules in single-molecule electronics. In this work, we designed and synthesized three analogous π-conjugated molecules, 1, 4-di(thiophen-2-yl)benzene (BT-H), 1, 4-bis(5 hexylthiophen-2-yl)benzene (BT-Hex) and 1, 4-bis(5-chlorothiophen-2-yl)benzene (BT-Cl). These molecules have the same backbone, but different substituents (H, C6 and Cl atoms, respectively) at position 4 of both end-capped thiophenes. Enabled by thiophene anchors, these molecules can be readily incorporated into the nano gaps between electrodes to form molecular junctions. Charge transport properties of three types of single molecule junctions are explored using scanning tunneling microscopy based break junction (STM-BJ) technique and the influence of different substituents at thiophene on the molecule-electrode binding modes are comparatively studied. Two separate binding modes with a conductance discrepancy of more than an order of magnitude are observed for all three molecules, with a high conductance state (GH) corresponding to a Au—π linked junction (Au electrode coupled with the thiophene π orbital) and a low conductance state (GL) originating from a Au—S binding scheme. Interestingly, the values of the GL state for three molecules are greatly affected by the different substituents at thiophenes, yielding a conductance trend of GBT-Hex > GBT-H > GBT-Cl. This can be explained by the electron affinity of different substituents, which shifts their highest occupied molecular orbital (HOMO) with respect to Au Fermi level and thus changes the energy barrier. In contrast, the GH state values of three molecules are not affected obviously by different substituents. We also statistically analyzed the formation rate of two binding modes for three molecules and found that the ratio between two binding modes can be changed with different addition of substituents. This work provides a useful method in modifying the binding properties of thiophene as an anchor group to gold and sheds light on a simple strategy in the design of anchor ligands. ![]()
The anchor group of a molecule determines its binding characteristics with electrodes. It impacts the molecular conductance of the formed single molecule junctions and is of great importance to the field of molecular electronics. Thiophene unit is an emerging anchor ligand and shows the ability to bind with Au electrodes. As a building block in designing organic photoelectric materials, thiophene has a potential in expanding the variety of target molecules in single-molecule electronics. In this work, we designed and synthesized three analogous π-conjugated molecules, 1, 4-di(thiophen-2-yl)benzene (BT-H), 1, 4-bis(5 hexylthiophen-2-yl)benzene (BT-Hex) and 1, 4-bis(5-chlorothiophen-2-yl)benzene (BT-Cl). These molecules have the same backbone, but different substituents (H, C6 and Cl atoms, respectively) at position 4 of both end-capped thiophenes. Enabled by thiophene anchors, these molecules can be readily incorporated into the nano gaps between electrodes to form molecular junctions. Charge transport properties of three types of single molecule junctions are explored using scanning tunneling microscopy based break junction (STM-BJ) technique and the influence of different substituents at thiophene on the molecule-electrode binding modes are comparatively studied. Two separate binding modes with a conductance discrepancy of more than an order of magnitude are observed for all three molecules, with a high conductance state (GH) corresponding to a Au—π linked junction (Au electrode coupled with the thiophene π orbital) and a low conductance state (GL) originating from a Au—S binding scheme. Interestingly, the values of the GL state for three molecules are greatly affected by the different substituents at thiophenes, yielding a conductance trend of GBT-Hex > GBT-H > GBT-Cl. This can be explained by the electron affinity of different substituents, which shifts their highest occupied molecular orbital (HOMO) with respect to Au Fermi level and thus changes the energy barrier. In contrast, the GH state values of three molecules are not affected obviously by different substituents. We also statistically analyzed the formation rate of two binding modes for three molecules and found that the ratio between two binding modes can be changed with different addition of substituents. This work provides a useful method in modifying the binding properties of thiophene as an anchor group to gold and sheds light on a simple strategy in the design of anchor ligands.
2023, 39(11): 221204
doi: 10.3866/PKU.WHXB202212042
Abstract:
Owing to the accelerated growth of the human economy and society, the increasing concentration of CO2 in the atmosphere has caused serious ecological and environmental problems because of the greenhouse effect. In response to the challenges posed by climate change, China has made a significant commitment to "peak carbon emissions by 2030 and achieve carbon neutrality by 2060". Ideally, converting CO2 into carbon-based energy and chemicals is supposed to be the best strategy of both worlds, mitigating the greenhouse effect while also addressing the shortage of energy supply. Among the proposed concepts for the above strategy, the scheme of reducing CO2 using renewable green H2 to produce chemicals is preferred, because it can stimulate the potential of clean energy while also reducing CO2 emission. To accelerate this reduction process, many catalytic reactions, including photocatalysis, have been designed and investigated. Owing to its high catalytic efficiency and extensive use of solar energy, photothermal catalytic CO2 hydrogenation in photocatalysis is desirable for increasing sun-to-fuel efficiency. There are two main interpretations of photothermal catalytic hydrogenation: (1) only sunlight is used as the energy source to drive the catalyst, which generates heat to promote CO2 conversion. In this case, the reaction still proceeds in the form of thermocatalysis, whereas photocatalysis has a limited effect. (2) Solar and heat energy are coupled to participate in the catalytic reaction, which has a synergistic effect. Therefore, according to the catalytic mode, the rational design and successful synthesis of photothermal catalysts are very important. Metal oxide semiconductors, owing to their unique energy band structure and chemical properties, high stability, and environmental friendliness, are widely used in the research of photothermal catalytic hydrogenation reactions. This paper reviews the research progress on metal oxide materials used in the CO2 hydrogenation reaction by photothermal catalysis. In particular, the most significant results of research in the last five years have been performed mainly from three different catalyst modulation strategies, such as supporting catalysts, applying microstructure engineering, and defect engineering. The mechanisms of these modulation strategies are summarized and presented for further understanding. In addition, this study introduces different types of photothermal hydrogenation reactors, accompanied by the effects of some key parameters on the reactions. Finally, design strategies for metal oxide catalysts are suggested, and an outlook of photothermal abatement technology is presented.![]()
Owing to the accelerated growth of the human economy and society, the increasing concentration of CO2 in the atmosphere has caused serious ecological and environmental problems because of the greenhouse effect. In response to the challenges posed by climate change, China has made a significant commitment to "peak carbon emissions by 2030 and achieve carbon neutrality by 2060". Ideally, converting CO2 into carbon-based energy and chemicals is supposed to be the best strategy of both worlds, mitigating the greenhouse effect while also addressing the shortage of energy supply. Among the proposed concepts for the above strategy, the scheme of reducing CO2 using renewable green H2 to produce chemicals is preferred, because it can stimulate the potential of clean energy while also reducing CO2 emission. To accelerate this reduction process, many catalytic reactions, including photocatalysis, have been designed and investigated. Owing to its high catalytic efficiency and extensive use of solar energy, photothermal catalytic CO2 hydrogenation in photocatalysis is desirable for increasing sun-to-fuel efficiency. There are two main interpretations of photothermal catalytic hydrogenation: (1) only sunlight is used as the energy source to drive the catalyst, which generates heat to promote CO2 conversion. In this case, the reaction still proceeds in the form of thermocatalysis, whereas photocatalysis has a limited effect. (2) Solar and heat energy are coupled to participate in the catalytic reaction, which has a synergistic effect. Therefore, according to the catalytic mode, the rational design and successful synthesis of photothermal catalysts are very important. Metal oxide semiconductors, owing to their unique energy band structure and chemical properties, high stability, and environmental friendliness, are widely used in the research of photothermal catalytic hydrogenation reactions. This paper reviews the research progress on metal oxide materials used in the CO2 hydrogenation reaction by photothermal catalysis. In particular, the most significant results of research in the last five years have been performed mainly from three different catalyst modulation strategies, such as supporting catalysts, applying microstructure engineering, and defect engineering. The mechanisms of these modulation strategies are summarized and presented for further understanding. In addition, this study introduces different types of photothermal hydrogenation reactors, accompanied by the effects of some key parameters on the reactions. Finally, design strategies for metal oxide catalysts are suggested, and an outlook of photothermal abatement technology is presented.
2023, 39(11): 230100
doi: 10.3866/PKU.WHXB202301001
Abstract:
The photocatalytic synthesis of hydrogen peroxide using earth-abundant water and/or O2 as raw materials and solar energy as the sole energy input is an attractive route to achieving a carbon-neutral future. In particular, semiconducting polymer photocatalysts have piqued the interest of researchers working on the photocatalytic synthesis of H2O2 because their bandgap structures, reactivation sites, and components are easily tunable at the molecular level. However, there are two major challenges: 1) the photoredox centers are difficult to separate and recombine easily, resulting in low reactivity in the photocatalytic production of H2O2, and 2) the low utilization rate of the redox centers. In several cases, only one side of the redox center is used for the photocatalytic synthesis of H2O2, while the other side typically reacts with a sacrificial agent. In this review, we provide a timely survey of recent advances in the spatial separation and synergistic utilization of photoredox centers for photocatalytic H2O2 production. The key aspect for achieving spatial separation of the redox centers is to engineer electron donor-acceptor (D-A) units on a single photocatalyst, such as by incorporating atomically dispersed metals into the polymer frameworks to build metal-organic D-A units or constructing all-organic D-A units. Depending on the photocatalytic behavior of the redox centers, the synergistic utilization of photoredox centers can be classified into three major reaction models: 1) the oxygen reduction reaction (ORR) combined with the oxidative production of chemicals; 2) the water oxidation reaction (WOR) combined with the reductive production of chemicals; and 3) the ORR combined with the WOR. Based on this, the regulation modes, characteristics, catalytic mechanisms, and reaction pathways to overcome the two challenges of efficient H2O2 production are summarized and discussed. Finally, we demonstrate efficient photocatalytic H2O2 production and provide prospects and challenges for the photocatalytic production of H2O2 using photoredox centers.![]()
The photocatalytic synthesis of hydrogen peroxide using earth-abundant water and/or O2 as raw materials and solar energy as the sole energy input is an attractive route to achieving a carbon-neutral future. In particular, semiconducting polymer photocatalysts have piqued the interest of researchers working on the photocatalytic synthesis of H2O2 because their bandgap structures, reactivation sites, and components are easily tunable at the molecular level. However, there are two major challenges: 1) the photoredox centers are difficult to separate and recombine easily, resulting in low reactivity in the photocatalytic production of H2O2, and 2) the low utilization rate of the redox centers. In several cases, only one side of the redox center is used for the photocatalytic synthesis of H2O2, while the other side typically reacts with a sacrificial agent. In this review, we provide a timely survey of recent advances in the spatial separation and synergistic utilization of photoredox centers for photocatalytic H2O2 production. The key aspect for achieving spatial separation of the redox centers is to engineer electron donor-acceptor (D-A) units on a single photocatalyst, such as by incorporating atomically dispersed metals into the polymer frameworks to build metal-organic D-A units or constructing all-organic D-A units. Depending on the photocatalytic behavior of the redox centers, the synergistic utilization of photoredox centers can be classified into three major reaction models: 1) the oxygen reduction reaction (ORR) combined with the oxidative production of chemicals; 2) the water oxidation reaction (WOR) combined with the reductive production of chemicals; and 3) the ORR combined with the WOR. Based on this, the regulation modes, characteristics, catalytic mechanisms, and reaction pathways to overcome the two challenges of efficient H2O2 production are summarized and discussed. Finally, we demonstrate efficient photocatalytic H2O2 production and provide prospects and challenges for the photocatalytic production of H2O2 using photoredox centers.
2023, 39(11): 221204
doi: 10.3866/PKU.WHXB202212048
Abstract:
Semiconductor-based photocatalysis is an efficient technology that reduces energy consumption and environmental pollution; however, it is impeded by Coulombic attraction-induced charge recombination, which reduces solar conversion efficiency. The internal electric field induced by heterointerface engineering, defect engineering, heteroatom doping, ferroelectric polarization, and polar surface terminations intervening in the uniform charge distribution can drive the directional migration of photogenerated electrons and holes, suppressing the charge recombination and back-reaction of intermediate species. However, the built-in electric field is static and easily shielded by internal active carriers and externally charged ions, which is detrimental to successive charge separation. Moreover, the internal electric field that relies solely on the structural design of the catalyst often requires complex preparation processes and is disqualified from simple and efficient solar energy conversion. By coupling the piezoelectric effect with the photoexcitation feature in piezo-photocatalysis, charge carrier dynamics can be persistently modulated. The noncentrosymmetric structures of piezoelectrics result in the deviation of positive and negative charge centers with the exerted external stress, generating nonzero dipole moments and polarization charges on the opposite terminals of the crystal. On the one hand, the polarized bound charges and initiated piezoelectric polarization field by mechanical stress promote the separation and transfer of photoinduced charges in both the bulk and on the surface of the catalyst, facilitating more active carriers to participate in the surface reaction. On the other hand, the accumulation of piezoelectric polarization charges on the surface contributes to the upward or downward bending of the band, which can flexibly manipulate the charge transfer behavior at the heterojunction interface, further steering the spatial distribution of electrons and holes. In addition, band tilting induced by piezoelectric polarization can also modulate the energy band structure of the catalyst to match the redox potential of the target reaction, breaking the intrinsic thermodynamic restriction. Hence, the coupling of solar and mechanical energy significantly improves the efficiency of catalytic energy conversion. As a complex reaction process of piezo-photocatalysis, diverse enhancement strategies have been implemented; however, there are few systematic and pertinent overviews for high-performance piezo-photocatalyst design. This study introduces the mechanism of piezoelectric polarization-enhanced photocatalysis and summarizes the catalytic enhancement strategy based on the piezo-photocatalysis reaction process, including morphology and polarization regulation, heterostructure construction, and surface engineering. Meanwhile, recent advances in piezo-photocatalysis for energy applications have been reviewed. Finally, the problems and challenges associated with the development of piezo-photocatalysis are analyzed and discussed.![]()
Semiconductor-based photocatalysis is an efficient technology that reduces energy consumption and environmental pollution; however, it is impeded by Coulombic attraction-induced charge recombination, which reduces solar conversion efficiency. The internal electric field induced by heterointerface engineering, defect engineering, heteroatom doping, ferroelectric polarization, and polar surface terminations intervening in the uniform charge distribution can drive the directional migration of photogenerated electrons and holes, suppressing the charge recombination and back-reaction of intermediate species. However, the built-in electric field is static and easily shielded by internal active carriers and externally charged ions, which is detrimental to successive charge separation. Moreover, the internal electric field that relies solely on the structural design of the catalyst often requires complex preparation processes and is disqualified from simple and efficient solar energy conversion. By coupling the piezoelectric effect with the photoexcitation feature in piezo-photocatalysis, charge carrier dynamics can be persistently modulated. The noncentrosymmetric structures of piezoelectrics result in the deviation of positive and negative charge centers with the exerted external stress, generating nonzero dipole moments and polarization charges on the opposite terminals of the crystal. On the one hand, the polarized bound charges and initiated piezoelectric polarization field by mechanical stress promote the separation and transfer of photoinduced charges in both the bulk and on the surface of the catalyst, facilitating more active carriers to participate in the surface reaction. On the other hand, the accumulation of piezoelectric polarization charges on the surface contributes to the upward or downward bending of the band, which can flexibly manipulate the charge transfer behavior at the heterojunction interface, further steering the spatial distribution of electrons and holes. In addition, band tilting induced by piezoelectric polarization can also modulate the energy band structure of the catalyst to match the redox potential of the target reaction, breaking the intrinsic thermodynamic restriction. Hence, the coupling of solar and mechanical energy significantly improves the efficiency of catalytic energy conversion. As a complex reaction process of piezo-photocatalysis, diverse enhancement strategies have been implemented; however, there are few systematic and pertinent overviews for high-performance piezo-photocatalyst design. This study introduces the mechanism of piezoelectric polarization-enhanced photocatalysis and summarizes the catalytic enhancement strategy based on the piezo-photocatalysis reaction process, including morphology and polarization regulation, heterostructure construction, and surface engineering. Meanwhile, recent advances in piezo-photocatalysis for energy applications have been reviewed. Finally, the problems and challenges associated with the development of piezo-photocatalysis are analyzed and discussed.
2023, 39(11): 230101
doi: 10.3866/PKU.WHXB202301012
Abstract:
Selective hydrogenation is an essential catalytic reaction in modern industrial chemistry. For instance, butene can be used to produce many important organic chemical products, but the catalytic cracking of naphtha to produce olefins also produces some diolefins, which contain approximately 0.2%–2.0% 1,3-butadiene. The selective hydrogenation of 1,3-butadiene is a crucial step in purifying single olefins and prevents poisoning of the catalysts used in polymerization. Currently, the most common industrially employed catalysts in the reaction are palladium-based catalysts, but drawbacks associated with these include high cost and low abundance. Transition metal Ni-based catalysts have the advantages of being low cost and having high hydrogenation activity, but they are prone to excessive hydrogenation in butadiene hydrogenation reactions. This leads to reduced selectivity and the loss of monoolefins in the feed gas. In addition, Ni-based catalysts tend to accumulate carbon on the surface, which results in catalyst deactivation. Therefore, designing Ni-based catalysts with excellent catalytic performance has been an industrial research priority. Herein, we synthesized Ni3Zn/Al2O3 catalysts by impregnation and achieved the alumina-supported Ni3ZnC0.7 structure by acetylene atmosphere treatment. Interstitial sites of the Ni3Zn intermetallic catalyst were modified by introducing interstitial carbon atoms. This enhances the catalytic performance of the 1,3-butadiene hydrogenation reaction. X-ray diffraction and transmission electron microscopy revealed that the catalyst presents a typical Ni3ZnC0.7 phase. The interstitial carbon structure can suppress excessive hydrogenation, exhibiting up to 93% butene selectivity at a 98% conversion of 1,3-butadiene, which renders it superior to the Ni3Zn/Al2O3 catalyst. More importantly, the selectivity to 1-butene is improved by approximately 40% compared to the Ni3Zn/Al2O3 intermetallic catalyst. In addition, the Ni3ZnC0.7/Al2O3 catalyst exhibits superior and stable selectivity within a wide H2/1,3-butadiene ratio range and can operate reliably under fluctuating conditions. CO-diffuse reflectance infrared Fourier transformed spectroscopy (CO-DRIFTS) demonstrated that coordinating the carbon atom in the interstitial site with the neighboring Ni atoms alters the electron structure of the Ni sites in the Ni3ZnC0.7 structure. The electrons at the surface Ni sites are transferred to the carbon atoms at the interstitial sites rendering Ni more electron-deficient and decreasing the adsorption strength of 1-butene, which inhibits the excessive hydrogenation reaction pathway. It is also noteworthy that the interstitial carbon structure can inhibit carbonaceous species formation and accumulation significantly improving the Ni3ZnC0.7/Al2O3 catalyst's stability. This work is significant for understanding the structure-performance relationship at the interstitial sites in transition metal catalysts. Furthermore, it provides new insights into the design of hydrogenation catalysts.![]()
Selective hydrogenation is an essential catalytic reaction in modern industrial chemistry. For instance, butene can be used to produce many important organic chemical products, but the catalytic cracking of naphtha to produce olefins also produces some diolefins, which contain approximately 0.2%–2.0% 1,3-butadiene. The selective hydrogenation of 1,3-butadiene is a crucial step in purifying single olefins and prevents poisoning of the catalysts used in polymerization. Currently, the most common industrially employed catalysts in the reaction are palladium-based catalysts, but drawbacks associated with these include high cost and low abundance. Transition metal Ni-based catalysts have the advantages of being low cost and having high hydrogenation activity, but they are prone to excessive hydrogenation in butadiene hydrogenation reactions. This leads to reduced selectivity and the loss of monoolefins in the feed gas. In addition, Ni-based catalysts tend to accumulate carbon on the surface, which results in catalyst deactivation. Therefore, designing Ni-based catalysts with excellent catalytic performance has been an industrial research priority. Herein, we synthesized Ni3Zn/Al2O3 catalysts by impregnation and achieved the alumina-supported Ni3ZnC0.7 structure by acetylene atmosphere treatment. Interstitial sites of the Ni3Zn intermetallic catalyst were modified by introducing interstitial carbon atoms. This enhances the catalytic performance of the 1,3-butadiene hydrogenation reaction. X-ray diffraction and transmission electron microscopy revealed that the catalyst presents a typical Ni3ZnC0.7 phase. The interstitial carbon structure can suppress excessive hydrogenation, exhibiting up to 93% butene selectivity at a 98% conversion of 1,3-butadiene, which renders it superior to the Ni3Zn/Al2O3 catalyst. More importantly, the selectivity to 1-butene is improved by approximately 40% compared to the Ni3Zn/Al2O3 intermetallic catalyst. In addition, the Ni3ZnC0.7/Al2O3 catalyst exhibits superior and stable selectivity within a wide H2/1,3-butadiene ratio range and can operate reliably under fluctuating conditions. CO-diffuse reflectance infrared Fourier transformed spectroscopy (CO-DRIFTS) demonstrated that coordinating the carbon atom in the interstitial site with the neighboring Ni atoms alters the electron structure of the Ni sites in the Ni3ZnC0.7 structure. The electrons at the surface Ni sites are transferred to the carbon atoms at the interstitial sites rendering Ni more electron-deficient and decreasing the adsorption strength of 1-butene, which inhibits the excessive hydrogenation reaction pathway. It is also noteworthy that the interstitial carbon structure can inhibit carbonaceous species formation and accumulation significantly improving the Ni3ZnC0.7/Al2O3 catalyst's stability. This work is significant for understanding the structure-performance relationship at the interstitial sites in transition metal catalysts. Furthermore, it provides new insights into the design of hydrogenation catalysts.
2023, 39(11): 230304
doi: 10.3866/PKU.WHXB202303046
Abstract:
