溶解
合金
Pourbaix图
吸附
铂金
氢氧化物
金属
电极电位
过渡金属
化学
电极
材料科学
标准电极电位
物理化学
无机化学
结晶学
电化学
冶金
催化作用
生物化学
作者
Feng Tian,Alfred B. Anderson
摘要
Theoretical studies of Pt and PtCo alloy electrode dissolutions in PEMFCs were made using adsorption energies from VASP slab band calculations on the metal surfaces in a linear Gibbs energy relationship. The reversible potential for Co−OH formation from oxidation of H2O on the Pt3Co(111) surface was calculated to be 0.50 V, which is significantly lower than the calculated 0.70 V reversible potential for Pt−OH formation on the Pt(111) surface. Co(OH)2 formation from oxidation of H2O on the Pt3Co(111) surface was calculated to take place at a lower potential than Pt(OH)2 formation on the Pt(111) surface, with the respective reversible potentials 0.58 and 1.92 V. These results for what may be the initial steps of anodic dissolution indicate that Co will dissolve at lower potential than Pt in the alloy surface and leave behind a Pt surface skin when the potential is >∼0.50 V. In addition, the reversible potential for OH formation on a step of edge atom on Pt(111) surface from oxidation of H2O was calculated to be 0.60 V, which is 0.10 V lower than reversible potential on the terrace sites, which implies that edge atoms are removed first. The final step of dissolution is believed to be the hydrolysis of the Pt2+ hydroxide, which considering the small equilibrium constant reported by Pourbaix, should proceed slowly.
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