物理化学学报 >> 1993, Vol. 9 >> Issue (04): 538-541.doi: 10.3866/PKU.WHXB19930421

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Co(III)离子在二氧化铅电极上的阳极形成

金世雄; 孙丰   

  1. 南开大学化学系，天津 300071
  • 收稿日期:1991-12-28 修回日期:1992-05-27 发布日期:1993-08-15
  • 通讯作者: 金世雄

Anodic Formation of the Co3+ ion at PbO2 Anode in Concentrated H2SO4 Solutions

Jin Shi-Xiong; Sun Feng   

  1. Department of Chemistry, Nankai University, Tianjin 300071
  • Received:1991-12-28 Revised:1992-05-27 Published:1993-08-15
  • Contact: Jin Shi-Xiong

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关键词: 二氧化铅电极, Co(II)离子, Co(III)离子

Abstract: The kinetic data related respectively to Co~(3+) anodic formation and O_2 anodic evolution at PbO_2 anode in 3.4 mol·kg~(-1) H_2SO_4+x mol·dm~(-3) COSO_4 (x=0.0501-0.350) and 0.2 mol·dm~(-3) CoSO_4+x mol·kg~(-1) H_2SO_4 (x=1.556-9.110) solutions were obtained by method of resolving the steady-state polarization curve. Steady-state φ～lgi relationships for Co~(3+) anodic formation reaction Tafel slope is close to 2.303RT/βF, whereas for O_2 anodic evolution it is close to 2.303RT/2βF (with β(?)0.5).
It is shown by experiment that the anodic formation of Co~(3+) and O_2 anodic evolution at PbO_2 anode in H_2SO_4 solutions are described by the equations:
i_1(O_2)=k_1a_W~4[Co~(2+)]exp2βφF/RT
i_2(Co~(3+))=k_2a_W[Co~(2+)]~(1.5)expβφF/RT
The experimental results may be explained by adopting the following scheme of electrode reactions
M+Co(H_2O)_6~(2-)+4H_2O→MCo(OH)_4(H_2O)_(2,ad)+4H_3O~++2e
2MCo(OH)_4(H_2O)_(2,ad)+2H_2O→O_2+2MCoO(H_2O)_(5,ad)
MCoO(H_2O)_(5,ad)+2H~+=M+Co(H_2O)_6~(2+)
MCo(OH)_4(H_2O)_(2,ad)+Co(H_2O)_6~(2+)→2Co(OH)_2(H_2O)_4~++M
Co(OH)_2(H_2O)_4~++2H~+=Co(H_2O)_6~(3+)
where M is an adsorption site on the PbO_2 anode.

Key words: PbO2 anode, Co(II) ion, Co(III) ion