Citation: Jin Shi-Xiong, Wen Qing. The Kinetics of the Anodic Oxidation of Ce(III) Ion at Pt Electrode in Sulfuric Acid Solution[J]. Acta Physico-Chimica Sinica, 1995, 11(08): 688-693. doi: 10.3866/PKU.WHXB19950804
硫酸溶液中Ce3+在铂电极上阳极氧化动力学
用分解极化曲线法研究了铂电极上Ce（Ⅳ）阳极形成动力学与机理．实验结果表明，电位在1．7—1．9V（vs．SCE）的高极化区，分解得到的O2和Ce（Ⅳ）的极化曲线Tafel斜率分别为2．303RT／βF和2×2．303RT／βF，两者的动力学方程可分别用下式表示：
i(O2)=k1aw4exp(βφF/RT)
i(Ce4+)=k2aw2[Ce3+]exp(βφF/2RT)
假设了Ce3＋是通过反应中间基MCe（OH）3•Oad氧化的机理．由此所导出的动力学方程与实验结果相符．
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关键词:
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Ce(IV)离子阳极形成
- / Ce(III)离子阳极氧化
- / 铂电极
English
The Kinetics of the Anodic Oxidation of Ce(III) Ion at Pt Electrode in Sulfuric Acid Solution
The kinetic data related respectively to Ce4+ anodic formation and O2 anodic evolution at Pt anode in 0.5mol•L-1H2SO4+x mol•L-1 Ce2(SO4)3 (x=0.01-0.1) and 0.025mol•L-1 Ce2(SO4)3 + xmol•L-1H2SO4 (x=1.09 - 4.20) solutions were obtained by method of resolving the steady-state polarization curve. From steady-state φ ~ lgi relationships for Ce4+ anodic formation reaction the Tafel slope is close to 2 ×2.303RT/βF, whereas for O2 anodic evolution it is close to 2.303RT/βF (with β = 0.5).
It was shown by experiments that the anodic formation of Ce4+ and O2 anodic evolution at Pt anode in mixed H2SO4-Ce2(SO4)3 solutions can be described by
i(O2)=k1aw4exp(βφF/RT)
i(Ce4+)=k2aw2[Ce3+]exp(βφF/2RT)
at high polarization region.
The experimental results of the high polarization region may be explained by the following scheme of electrode reactions
M+Ce3+=MCead3+
MCead3++4H2O→MCe(OH)4ad+4H++e
MCe(OH)4ad= MCe(OH)3Oad+H++e
2 MCe(OH)3Oad→2MCe(OH)3ad+O2
MCe(OH)3Oad+3H+= MCead3+3H2O
MCe(OH)3Oad+Ce3+→M+2CeO2+3H+
CeO2+4H+=Ce4++2H2O
where M is an adsorption site on the Pt-oxide.
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Key words:
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Pt anode
- / Ce(III) ion
- / Ce(IV) ion
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