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2018 Volume 39 Issue 10
2018, 39(10):
Abstract:
2018, 39(10): 1575-1593
doi: 10.1016/S1872-2067(18)63130-4
Abstract:
Oxygen evolution reaction (OER), as an important half-reaction involved in water splitting, has been intensely studied since the last century. Transition metal phosphide and sulfide-based compounds have attracted increasing attention as active OER catalysts due to their excellent physical and chemical characters, and massive efforts have been devoted to improving the phosphide and sulfide-based materials with better activity and stability in recent years. In this review, the recent progress on phosphide and sulfide-based OER electrocatalysts in terms of chemical properties, synthetic methodologies, catalytic performances evaluation and improvement strategy is reviewed. The most accepted reaction pathways as well as the thermodynamics and electrochemistry of the OER are firstly introduced in brief, followed by a summary of the recent research and optimization strategy of phosphide and sulfide-based OER electrocatalysts. Finally, some mechanistic studies of the active phase of phosphide and sulfide-based compounds are discussed to give insight into the nature of active catalytic sites. It is expected to indicate guidance for further improving the performances of phosphide and sulfide-based OER electrocatalysts.
Oxygen evolution reaction (OER), as an important half-reaction involved in water splitting, has been intensely studied since the last century. Transition metal phosphide and sulfide-based compounds have attracted increasing attention as active OER catalysts due to their excellent physical and chemical characters, and massive efforts have been devoted to improving the phosphide and sulfide-based materials with better activity and stability in recent years. In this review, the recent progress on phosphide and sulfide-based OER electrocatalysts in terms of chemical properties, synthetic methodologies, catalytic performances evaluation and improvement strategy is reviewed. The most accepted reaction pathways as well as the thermodynamics and electrochemistry of the OER are firstly introduced in brief, followed by a summary of the recent research and optimization strategy of phosphide and sulfide-based OER electrocatalysts. Finally, some mechanistic studies of the active phase of phosphide and sulfide-based compounds are discussed to give insight into the nature of active catalytic sites. It is expected to indicate guidance for further improving the performances of phosphide and sulfide-based OER electrocatalysts.
2018, 39(10): 1594-1598
doi: 10.1016/S1872-2067(18)63088-8
Abstract:
A new method was developed to diastereoselectively synthesize polysubstituted 1,2-diamine compounds from the reaction of diazoesters with arylamines and diaryl imines by using the dioxazoline ligand L2-ligated silver catalyst. The Lewis acidity of the silver catalyst affected the different types of substrate diastereoselectivities; It also led to the formation of amine-exchange side products.
A new method was developed to diastereoselectively synthesize polysubstituted 1,2-diamine compounds from the reaction of diazoesters with arylamines and diaryl imines by using the dioxazoline ligand L2-ligated silver catalyst. The Lewis acidity of the silver catalyst affected the different types of substrate diastereoselectivities; It also led to the formation of amine-exchange side products.
2018, 39(10): 1599-1607
doi: 10.1016/S1872-2067(18)63105-5
Abstract:
Bimetallic nanostructures have attracted great interest as efficient catalyst to enhance activity, selectivity and stability in catalytical conversion. Herein, we report a facile one-pot carbothermal route to in-situ controllable synthesize heterogeneous bimetallic Ni3Fe NPs@C nanocatalyst. The X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and N2 adsorption-description results reveal that the Ni3Fe alloy nanoparticles are evenly embedded in carbon matrix. The as-prepared Ni3Fe NPs@C catalyst shows excellent selective hydrogenation catalytic performance toward the conversion of levulinic acid (LA) to γ-valerolactone (GVL) via both direct hydrogenation (DH) and transfer hydrogenation (TH). In DH of LA, the bimetallic catalyst achieved a 93.8% LA conversion efficiency with a 95.5% GVL selectivity and 38.2 mmol g-1 h-1 GVL productivity (under 130℃, 2MPa H2within 2 h), which are 6 and 40 times in comparison with monometallic Ni NPs@C and Fe NPs@C catalysts, respectively. In addition, the identical catalyst displayed a full conversion of LA with almost 100% GVL selectivity and 167.1 mmol g-1 h-1 GVL productivity at 180℃ within 0.5 h in TH of LA. Under optimal reaction conditions, the DH and TH catalytic performance of 500-Ni3Fe NPs@C(3:1) catalyst for converting LA to GVL is comparable to the state-of-the-art noble-based catalysts. The demonstrated capability of bimetallic catalyst design approach to introduce dual-catalytic functionality for DH and TH reactions could be adoptable for other catalysis processes.
Bimetallic nanostructures have attracted great interest as efficient catalyst to enhance activity, selectivity and stability in catalytical conversion. Herein, we report a facile one-pot carbothermal route to in-situ controllable synthesize heterogeneous bimetallic Ni3Fe NPs@C nanocatalyst. The X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and N2 adsorption-description results reveal that the Ni3Fe alloy nanoparticles are evenly embedded in carbon matrix. The as-prepared Ni3Fe NPs@C catalyst shows excellent selective hydrogenation catalytic performance toward the conversion of levulinic acid (LA) to γ-valerolactone (GVL) via both direct hydrogenation (DH) and transfer hydrogenation (TH). In DH of LA, the bimetallic catalyst achieved a 93.8% LA conversion efficiency with a 95.5% GVL selectivity and 38.2 mmol g-1 h-1 GVL productivity (under 130℃, 2MPa H2within 2 h), which are 6 and 40 times in comparison with monometallic Ni NPs@C and Fe NPs@C catalysts, respectively. In addition, the identical catalyst displayed a full conversion of LA with almost 100% GVL selectivity and 167.1 mmol g-1 h-1 GVL productivity at 180℃ within 0.5 h in TH of LA. Under optimal reaction conditions, the DH and TH catalytic performance of 500-Ni3Fe NPs@C(3:1) catalyst for converting LA to GVL is comparable to the state-of-the-art noble-based catalysts. The demonstrated capability of bimetallic catalyst design approach to introduce dual-catalytic functionality for DH and TH reactions could be adoptable for other catalysis processes.
2018, 39(10): 1608-1614
doi: 10.1016/S1872-2067(18)63136-5
Abstract:
The supported Au nanoparticles have been regarded as promising catalysts for CO oxidation but still suffer from unsatisfactory catalytic activity and durability. Herein, we show a simple and efficient strategy to simultaneously enhance the catalytic activity and durability for CO oxidation. Key to the success is modification of the supported Au nanoparticle catalyst with nanosized CeOx to construct abundant Au-CeOx interface. Owing to the maximized interfacial effect on the CeOx-modified Au nanoparticles, the concentration of positively-charged Au species (Auδ+) was remarkably improved, leading to enhanced catalytic activities in the oxidation of CO. Importantly, the stability of Au nanoparticles is remarkably increased by CeOx modification, exhibiting good durability in a continuous test of CO oxidation at higher temperatures.
The supported Au nanoparticles have been regarded as promising catalysts for CO oxidation but still suffer from unsatisfactory catalytic activity and durability. Herein, we show a simple and efficient strategy to simultaneously enhance the catalytic activity and durability for CO oxidation. Key to the success is modification of the supported Au nanoparticle catalyst with nanosized CeOx to construct abundant Au-CeOx interface. Owing to the maximized interfacial effect on the CeOx-modified Au nanoparticles, the concentration of positively-charged Au species (Auδ+) was remarkably improved, leading to enhanced catalytic activities in the oxidation of CO. Importantly, the stability of Au nanoparticles is remarkably increased by CeOx modification, exhibiting good durability in a continuous test of CO oxidation at higher temperatures.
2018, 39(10): 1615-1624
doi: 10.1016/S1872-2067(18)63131-6
Abstract:
Porous C-I codoped carbon nitride materials were synthesized by in-situ codoping with iodized ionic liquid followed by post-thermal treatment in air. The effects of doping content of C-I codoping with different amounts of ionic liquid on the structural, optical and photocatalytic properties of the samples were investigated. Characterization results show that more compact interlayer sacking can be achieved by post-thermal treatment. Combined with C-I codoping by insertion of ionic liquids, much enlarged surface area but optimized sp2 conjugated heterocyclic structure can be found in the catalysts. Optical and energy band analysis results evidence that the light absorptions especially in visible light region are significantly improved. Although the band gap of porous C-I codoped samples enlarge because of the generation of porous, the negatively shifted conduction band position thermodynamically supplies stronger motivation for water reduction. Photoelectricity tests reveal that the photo-induced electron density was increased after C-I codoping modification. Also, the recombination rate of electron-hole pairs is remarkably inhibited. The catalysts with moderate C-I codoing content perform sharply enhanced photocatalytic H2 evolution activity under visible light irradiation. A H2 evolution rate of 168.2 μmol/h was achieved and it was more than 9.8 times higher than pristine carbon nitride. This study demonstrates a novel non-metal doping strategy for synthesis and optimization of polymer semiconductor with gratifying photocatalytic H2 evolution performance from water hydrolysis.
Porous C-I codoped carbon nitride materials were synthesized by in-situ codoping with iodized ionic liquid followed by post-thermal treatment in air. The effects of doping content of C-I codoping with different amounts of ionic liquid on the structural, optical and photocatalytic properties of the samples were investigated. Characterization results show that more compact interlayer sacking can be achieved by post-thermal treatment. Combined with C-I codoping by insertion of ionic liquids, much enlarged surface area but optimized sp2 conjugated heterocyclic structure can be found in the catalysts. Optical and energy band analysis results evidence that the light absorptions especially in visible light region are significantly improved. Although the band gap of porous C-I codoped samples enlarge because of the generation of porous, the negatively shifted conduction band position thermodynamically supplies stronger motivation for water reduction. Photoelectricity tests reveal that the photo-induced electron density was increased after C-I codoping modification. Also, the recombination rate of electron-hole pairs is remarkably inhibited. The catalysts with moderate C-I codoing content perform sharply enhanced photocatalytic H2 evolution activity under visible light irradiation. A H2 evolution rate of 168.2 μmol/h was achieved and it was more than 9.8 times higher than pristine carbon nitride. This study demonstrates a novel non-metal doping strategy for synthesis and optimization of polymer semiconductor with gratifying photocatalytic H2 evolution performance from water hydrolysis.
2018, 39(10): 1625-1632
doi: 10.1016/S1872-2067(18)63108-0
Abstract:
The asymmetric reductive amination of achiral ketones with ammonia is a particularly attractive reaction for the synthesis of chiral amines. Although several engineered amine dehydrogenases have been developed by protein engineering for the asymmetric reductive amination of ketones, they all display (R)-stereoselectivity. To date, there is no report of an (S)-stereoselective biocatalyst for this reaction. Herein, a microorganism named Brevibacterium epidermidis ECU1015 that catalyzes the (S)-selective reductive amination of ketones with ammonium has been successfully isolated from soil. Using B. epidermidis ECU1015 as the catalyst, the asymmetric reductive amination of a set of phenylacetone derivatives was successfully carried out, yielding the corresponding (S)-chiral amines with moderate conversion and >99% enantiomeric excess.
The asymmetric reductive amination of achiral ketones with ammonia is a particularly attractive reaction for the synthesis of chiral amines. Although several engineered amine dehydrogenases have been developed by protein engineering for the asymmetric reductive amination of ketones, they all display (R)-stereoselectivity. To date, there is no report of an (S)-stereoselective biocatalyst for this reaction. Herein, a microorganism named Brevibacterium epidermidis ECU1015 that catalyzes the (S)-selective reductive amination of ketones with ammonium has been successfully isolated from soil. Using B. epidermidis ECU1015 as the catalyst, the asymmetric reductive amination of a set of phenylacetone derivatives was successfully carried out, yielding the corresponding (S)-chiral amines with moderate conversion and >99% enantiomeric excess.
2018, 39(10): 1633-1645
doi: 10.1016/S1872-2067(18)63087-6
Abstract:
Production of biodiesel by the transesterification process using different modified graphene-based materials as catalysts was studied. Solid acid graphene-based samples were prepared by grafting sulfonic or phosphate groups on the surface of thermally reduced graphene oxide. The obtained materials were thoroughly characterized using scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, N2 adsorption-desorption measurements, potentiometric titration, elemental analysis, and Fourier transform infrared spectroscopy. The prepared catalysts were tested in the transesterification of rapeseed oil with methanol at 130℃ under pressure, and their activities were compared to the performance of a commercially available heterogeneous acidic catalyst, Amberlyst-15. All modified samples were active in the transesterification process; however, significant differences were observed in the yield of biodiesel, depending on the method of catalyst preparation and strength of the acidic sites. The highest yield of fatty acid methyl esters of 70% was obtained for thermally reduced graphene oxide functionalized with 4-benzenediazonium sulfonate after 6 h of processing, and this result was much higher than that obtained for the commercial catalyst Amberlyst-15. The results of the reusability test were also promising.
Production of biodiesel by the transesterification process using different modified graphene-based materials as catalysts was studied. Solid acid graphene-based samples were prepared by grafting sulfonic or phosphate groups on the surface of thermally reduced graphene oxide. The obtained materials were thoroughly characterized using scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, N2 adsorption-desorption measurements, potentiometric titration, elemental analysis, and Fourier transform infrared spectroscopy. The prepared catalysts were tested in the transesterification of rapeseed oil with methanol at 130℃ under pressure, and their activities were compared to the performance of a commercially available heterogeneous acidic catalyst, Amberlyst-15. All modified samples were active in the transesterification process; however, significant differences were observed in the yield of biodiesel, depending on the method of catalyst preparation and strength of the acidic sites. The highest yield of fatty acid methyl esters of 70% was obtained for thermally reduced graphene oxide functionalized with 4-benzenediazonium sulfonate after 6 h of processing, and this result was much higher than that obtained for the commercial catalyst Amberlyst-15. The results of the reusability test were also promising.
2018, 39(10): 1646-1652
doi: 10.1016/S1872-2067(18)63098-0
Abstract:
Novel catalytic systems for the Rh-catalyzed hydroformylation of dicyclopentadiene have been developed using tris-H8-binaphthyl monophosphite as ligands containing different ester substituents at the 2'-binaphthyl position (OCOMe, OCOPh, OCOAdamantyl and OCOPhCl). The catalysts exhibited high activity (S/C=4000, TON=3286) with good to excellent selectivity towards dialdehydes. Remarkably, the Rh(I) complex bearing the ligands with chlorophenyl ester substituents led to 99.9% conversion and 98.7% selectivity for dialdehydes under relatively mild conditions (6 MPa, 120℃).
Novel catalytic systems for the Rh-catalyzed hydroformylation of dicyclopentadiene have been developed using tris-H8-binaphthyl monophosphite as ligands containing different ester substituents at the 2'-binaphthyl position (OCOMe, OCOPh, OCOAdamantyl and OCOPhCl). The catalysts exhibited high activity (S/C=4000, TON=3286) with good to excellent selectivity towards dialdehydes. Remarkably, the Rh(I) complex bearing the ligands with chlorophenyl ester substituents led to 99.9% conversion and 98.7% selectivity for dialdehydes under relatively mild conditions (6 MPa, 120℃).
2018, 39(10): 1653-1663
doi: 10.1016/S1872-2067(18)63099-2
Abstract:
Low-temperature selective catalytic reduction (SCR) of NO with NH3 was tested over Ho-doped Mn-Ce/TiO2 catalysts prepared by the impregnation method. The obtained catalysts with different Ho doping ratios were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), temperature-programmed reduction (H2-TPR), temperature-programmed desorption of NH3 (NH3-TPD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The catalytic activities were tested on a fixed bed. Their results indicated that the proper doping amount of Ho could effectively improve the low-temperature denitrification performance and the SO2 resistance of Mn-Ce/TiO2 catalyst. The catalyst with Ho/Ti of 0.1 presented excellent catalytic activity, with a conversion of more than 90% in the temperature window of 140-220℃. The characterization results showed that the improved SCR activity of the Mn-Ce/TiO2 catalyst caused by Ho doping was due to the increase of the specific surface area, higher concentration of chemisorbed oxygen, higher surface Mn4+/Mn3+ ratio, and higher acidity. The SO2 resistance test showed that the deactivating influence of SO2 on the catalyst was irreversible. The XRD and XPS results showed that the main reason for the catalyst deactivation was sulfates that had formed on the catalyst surface and that Ho doping could inhibit the sulfation to some extent.
Low-temperature selective catalytic reduction (SCR) of NO with NH3 was tested over Ho-doped Mn-Ce/TiO2 catalysts prepared by the impregnation method. The obtained catalysts with different Ho doping ratios were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), temperature-programmed reduction (H2-TPR), temperature-programmed desorption of NH3 (NH3-TPD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The catalytic activities were tested on a fixed bed. Their results indicated that the proper doping amount of Ho could effectively improve the low-temperature denitrification performance and the SO2 resistance of Mn-Ce/TiO2 catalyst. The catalyst with Ho/Ti of 0.1 presented excellent catalytic activity, with a conversion of more than 90% in the temperature window of 140-220℃. The characterization results showed that the improved SCR activity of the Mn-Ce/TiO2 catalyst caused by Ho doping was due to the increase of the specific surface area, higher concentration of chemisorbed oxygen, higher surface Mn4+/Mn3+ ratio, and higher acidity. The SO2 resistance test showed that the deactivating influence of SO2 on the catalyst was irreversible. The XRD and XPS results showed that the main reason for the catalyst deactivation was sulfates that had formed on the catalyst surface and that Ho doping could inhibit the sulfation to some extent.
2018, 39(10): 1664-1671
doi: 10.1016/S1872-2067(18)63109-2
Abstract:
We recently reported an N-doped mesoporous carbon (N-MC) extrudate, with major quaternary N species, prepared by a cheap and convenient method through direct carbonization of wheat flour with silica, which has excellent catalytic performance in acetylene hydrochlorination. Herein, we examined the activity of Au supported on N-MC (Au/N-MC) and compared it with that of Ausupported on nitrogen-free mesoporous carbon (Au/MC). The acetylene conversion of Au/N-MC was 50% at 180℃ with an acetylene space velocity of 600 h-1 and VHCl/VC2H2 of 1.1, which was double the activity of Au/MC (25%). The introduced nitrogen atoms acted as anchor sites that stabilized the Au3+ species and inhibited the reduction of Au3+ to Au0 during the preparation of Au/N-MC catalysts.
We recently reported an N-doped mesoporous carbon (N-MC) extrudate, with major quaternary N species, prepared by a cheap and convenient method through direct carbonization of wheat flour with silica, which has excellent catalytic performance in acetylene hydrochlorination. Herein, we examined the activity of Au supported on N-MC (Au/N-MC) and compared it with that of Ausupported on nitrogen-free mesoporous carbon (Au/MC). The acetylene conversion of Au/N-MC was 50% at 180℃ with an acetylene space velocity of 600 h-1 and VHCl/VC2H2 of 1.1, which was double the activity of Au/MC (25%). The introduced nitrogen atoms acted as anchor sites that stabilized the Au3+ species and inhibited the reduction of Au3+ to Au0 during the preparation of Au/N-MC catalysts.
2018, 39(10): 1672-1682
doi: 10.1016/S1872-2067(18)63115-8
Abstract:
The synergistic effect of high voltage discharge non-thermal plasma (NTP) and photocatalysts on contaminant removal has repeatedly confirmed by plenty of researches. Most previous plasma-photocatalyst synergistic systems focused on the utilization of the ultraviolet light but ignored the visible light generated by high voltage discharge. Graphitic carbon nitride (g-C3N4), a metal-free semiconductor that exhibits high chemical stability, can utilize both the ultraviolet and visible light from high voltage discharge. However, the synergistic system of NTP and g-C3N4 has been researched little. In this paper, the effect of NTP generated by dielectric barrier discharge (DBD) on g-C3N4is studied by comparing the photocatalytic activities, the surface physical structure and the surface chemical characteristics of pristine and plasma treated g-C3N4. Experimental results indicate that the DBD plasma can change the physical structure and the chemical characteristics and to further affect the photocatalytic activity of g-C3N4. The effect of NTP on g-C3N4is associated with the discharge intensity and the discharge time. For a long time scale, the effect of NTP on g-C3N4 photocatalysts presents a periodic change trend.
The synergistic effect of high voltage discharge non-thermal plasma (NTP) and photocatalysts on contaminant removal has repeatedly confirmed by plenty of researches. Most previous plasma-photocatalyst synergistic systems focused on the utilization of the ultraviolet light but ignored the visible light generated by high voltage discharge. Graphitic carbon nitride (g-C3N4), a metal-free semiconductor that exhibits high chemical stability, can utilize both the ultraviolet and visible light from high voltage discharge. However, the synergistic system of NTP and g-C3N4 has been researched little. In this paper, the effect of NTP generated by dielectric barrier discharge (DBD) on g-C3N4is studied by comparing the photocatalytic activities, the surface physical structure and the surface chemical characteristics of pristine and plasma treated g-C3N4. Experimental results indicate that the DBD plasma can change the physical structure and the chemical characteristics and to further affect the photocatalytic activity of g-C3N4. The effect of NTP on g-C3N4is associated with the discharge intensity and the discharge time. For a long time scale, the effect of NTP on g-C3N4 photocatalysts presents a periodic change trend.
2018, 39(10): 1683-1694
doi: 10.1016/S1872-2067(18)63123-7
Abstract:
A series of three-dimensionally ordered macroporous (3DOM) SnO2-based catalysts modified by the cations Ce4+, Mn3+, and Cu2+ have been prepared by using a colloidal crystal templating method and tested for soot combustion under loose contact condition. XRD and STEM mapping results confirm that all the secondary metal cations have entered the lattice matrix of tetragonal rutile SnO2 to form non-continuous solid solutions, thus impeding crystallization and improving the surface areas and pore volumes of the modified catalysts. In comparison with regular SnO2 nanoparticles, the 3DOM SnO2 displays evidently improved activity, testifying that the formation of the 3DOM structure can anchor the soot particulates in the macro-pores, which ensures that the contact of the soot particles with the active sites on the 3DOM skeleton is more easily formed, thus benefiting the target reaction. With the incorporation of the secondary metal cations, the activity of the catalyst can be further improved due to the formation of more abundant mobile oxygen species. In summary, these effects are believed to be the major factors responsible for the activity of the catalyst.
A series of three-dimensionally ordered macroporous (3DOM) SnO2-based catalysts modified by the cations Ce4+, Mn3+, and Cu2+ have been prepared by using a colloidal crystal templating method and tested for soot combustion under loose contact condition. XRD and STEM mapping results confirm that all the secondary metal cations have entered the lattice matrix of tetragonal rutile SnO2 to form non-continuous solid solutions, thus impeding crystallization and improving the surface areas and pore volumes of the modified catalysts. In comparison with regular SnO2 nanoparticles, the 3DOM SnO2 displays evidently improved activity, testifying that the formation of the 3DOM structure can anchor the soot particulates in the macro-pores, which ensures that the contact of the soot particles with the active sites on the 3DOM skeleton is more easily formed, thus benefiting the target reaction. With the incorporation of the secondary metal cations, the activity of the catalyst can be further improved due to the formation of more abundant mobile oxygen species. In summary, these effects are believed to be the major factors responsible for the activity of the catalyst.
2018, 39(10): 1695-1703
doi: 10.1016/S1872-2067(18)63097-9
Abstract:
Understanding the performance of reactive oxygen species (ROS) in photocatalysis is pivotal for advancing their application in environmental remediation. However, techniques for investigating the generation and transformation mechanism of ROS have been largely overlooked. In this study, considering g-C3N4 to be a model photocatalyst, we have focused on the ROS generation and transformation for efficient photocatalytic NO removal. It was found that the key to improving the photocatalysis performance was to enhance the ROS transformation from ·O2- to ·OH, elevating the production of ·OH. The ROS directly participate in the photocatalytic NO removal and tailor the rate-determining step, which is required to overcome the high activation energy of the intermediate conversion. Using a closely combined experimental and theoretical method, this work provides a new protocol to investigate the ROS behavior on g-C3N4 for effective NO removal and clarifies the reaction mechanism at the atomic level, which enriches the understanding of ROS in photocatalytic environmental remediation.
Understanding the performance of reactive oxygen species (ROS) in photocatalysis is pivotal for advancing their application in environmental remediation. However, techniques for investigating the generation and transformation mechanism of ROS have been largely overlooked. In this study, considering g-C3N4 to be a model photocatalyst, we have focused on the ROS generation and transformation for efficient photocatalytic NO removal. It was found that the key to improving the photocatalysis performance was to enhance the ROS transformation from ·O2- to ·OH, elevating the production of ·OH. The ROS directly participate in the photocatalytic NO removal and tailor the rate-determining step, which is required to overcome the high activation energy of the intermediate conversion. Using a closely combined experimental and theoretical method, this work provides a new protocol to investigate the ROS behavior on g-C3N4 for effective NO removal and clarifies the reaction mechanism at the atomic level, which enriches the understanding of ROS in photocatalytic environmental remediation.
2018, 39(10): 1704-1710
doi: 10.1016/S1872-2067(18)63127-4
Abstract:
In this study, CuBi2O4 photocathodes were prepared using a simple electrodeposition method for photoelectrochemical (PEC) hydrogen production. The prepared photocathodes were modified with amorphous TiO2 and a Pt co-catalyst, which resulted in the formation of CuBi2O4/TiO2 p-n heterojunctions, and enhanced the activities of the as-prepared photocathodes. The novel Pt/TiO2/CuBi2O4 photocathode exhibited a photocurrent of 0.35 mA/cm2 at 0.60 V vs. Reversible Hydrogen Electrode (RHE), which was nearly twice that of the Pt/CuBi2O4 photocathode. The present study provides a facile method for increasing the efficiency of photocathodes and provides meaningful guidance for the preparation of high-performance CuBi2O4 photocathodes.
In this study, CuBi2O4 photocathodes were prepared using a simple electrodeposition method for photoelectrochemical (PEC) hydrogen production. The prepared photocathodes were modified with amorphous TiO2 and a Pt co-catalyst, which resulted in the formation of CuBi2O4/TiO2 p-n heterojunctions, and enhanced the activities of the as-prepared photocathodes. The novel Pt/TiO2/CuBi2O4 photocathode exhibited a photocurrent of 0.35 mA/cm2 at 0.60 V vs. Reversible Hydrogen Electrode (RHE), which was nearly twice that of the Pt/CuBi2O4 photocathode. The present study provides a facile method for increasing the efficiency of photocathodes and provides meaningful guidance for the preparation of high-performance CuBi2O4 photocathodes.
2018, 39(10): 1711-1723
doi: 10.1016/S1872-2067(18)63110-9
Abstract:
Selective hydrogenolysis of biomass-derived furfuryl alcohol (FFA) to 1,5-and 1,2-pentanediol (PeD) was conducted over Cu-LaCoO3 catalysts with different Cu loadings; the catalysts were derived from perovskite structures prepared by a one-step citrate complexing method. The catalytic performances of the Cu-LaCoO3 catalysts were found to depend on the Cu loading and pretreatment conditions. The catalyst with 10 wt% Cu loading exhibited the best catalytic performance after prereduction in 5% H2-95% N2, achieving a high FFA conversion of 100% and selectivity of 55.5% for 1,5-pentanediol (40.3%) and 1,2-pentanediol (15.2%) at 413 K and 6 MPa H2. This catalyst could be reused four times without a loss of FFA conversion but it resulted in a slight decrease in pentanediol selectivity. Correlation between the structural changes in the catalysts at different states and the simultaneous variation in the catalytic performance revealed that cooperative catalysis between Cu0 and CoO promoted the hydrogenolysis of FFA to PeDs, especially to 1,5-PeD, while Co0 promoted the hydrogenation of FFA to tetrahydrofurfuryl alcohol (THFA). Therefore, it is suggested that a synergetic effect between balanced Cu0 and CoO sites plays a critical role in achieving a high yield of PeDs with a high 1,5-/1,2-pentanediol selectivity ratio during FFA hydrogenolysis.
Selective hydrogenolysis of biomass-derived furfuryl alcohol (FFA) to 1,5-and 1,2-pentanediol (PeD) was conducted over Cu-LaCoO3 catalysts with different Cu loadings; the catalysts were derived from perovskite structures prepared by a one-step citrate complexing method. The catalytic performances of the Cu-LaCoO3 catalysts were found to depend on the Cu loading and pretreatment conditions. The catalyst with 10 wt% Cu loading exhibited the best catalytic performance after prereduction in 5% H2-95% N2, achieving a high FFA conversion of 100% and selectivity of 55.5% for 1,5-pentanediol (40.3%) and 1,2-pentanediol (15.2%) at 413 K and 6 MPa H2. This catalyst could be reused four times without a loss of FFA conversion but it resulted in a slight decrease in pentanediol selectivity. Correlation between the structural changes in the catalysts at different states and the simultaneous variation in the catalytic performance revealed that cooperative catalysis between Cu0 and CoO promoted the hydrogenolysis of FFA to PeDs, especially to 1,5-PeD, while Co0 promoted the hydrogenation of FFA to tetrahydrofurfuryl alcohol (THFA). Therefore, it is suggested that a synergetic effect between balanced Cu0 and CoO sites plays a critical role in achieving a high yield of PeDs with a high 1,5-/1,2-pentanediol selectivity ratio during FFA hydrogenolysis.
