物理化学学报 >> 1995, Vol. 11 >> Issue (08): 688-693.doi: 10.3866/PKU.WHXB19950804

研究论文 上一篇    下一篇

硫酸溶液中Ce3+在铂电极上阳极氧化动力学

金世雄,温青   

  1. 南开大学化学系|天津 300071
  • 收稿日期:1994-06-27 修回日期:1994-09-28 发布日期:1995-08-15
  • 通讯作者: 金世雄

The Kinetics of the Anodic Oxidation of Ce(III) Ion at Pt Electrode in Sulfuric Acid Solution

Jin Shi-Xiong,Wen Qing   

  1. Department of Chemistry,Nankai University,Tianjin 300071
  • Received:1994-06-27 Revised:1994-09-28 Published:1995-08-15
  • Contact: Jin Shi-Xiong

摘要:

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.

关键词: Ce(IV)离子阳极形成, Ce(III)离子阳极氧化, 铂电极

Abstract:

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.

Key words: Pt anode, Ce(III) ion, Ce(IV) ion, Anodic kinetics, Oxygen evolution