摘要
Electrocatalytic activity is influenced by the surface charge on the solid catalyst.Conventionally,our attention has been focused on how the surface charge shapes the electric potential and concentration of ionic reactant(s)in the local reaction zone.Taking H_(2)O_(2)redox reactions at Pt(111)as a model system,we reveal a peculiar surface charge effect using ab initio molecular dynamics simulations of electrified Pt(111)-water interfaces.In this scenario,the negative surface charge on Pt(111)repels the O-O bond of the reactant(H_(2)O_(2))farther away from the electrode surface.This leads to a higher activation barrier for breaking the O-O bond.Incorporating this microscopic mechanism into a microkinetic-double-layer model,we are able to semi-quantitatively interpret the pH-dependent activity of H_(2)O_(2)redox reactions at Pt(111),especially the anomalously suppressed activity of H_(2)O_(2)reduction with decreasing electrode potential.The relevance of the present surface charge effect is also examined in wider scenarios with different electrolyte cations,solution pHs,crystal facets of the catalyst,and model parameters.In contrast with previous mechanisms focusing on how surface charge influences the local reaction condition at a fixed reaction plane,the present work gives an example in which the location of the reaction plane is adjusted by the surface charge.
固体催化剂表面电荷会影响其电催化活性.目前,科研人员主要关注的是表面电荷如何影响局部反应区中电势和离子浓度.本文以Pt(111)上的H_(2)O_(2)氧化还原反应为模型,利用从头算分子动力学模拟研究了Pt(111)-水界面的特殊表面电荷效应.Pt(111)上的负表面电荷排斥反应物(H_(2)O_(2))的O-O键,使其远离电极表面,从而导致O-O键断裂的活化能更高.进一步建立了双电层微观动力学模型,定量解释了Pt(111)上H_(2)O_(2)氧化还原反应的pH活性依赖,尤其是电极电位降低时H_(2)O_(2)还原活性的异常抑制.还探讨了该表面电荷效应在不同电解质阳离子、溶液pH值、催化剂晶面和模型参数等情况下的适用性,与其他侧重于表面电荷对固定反应面上局部反应条件的影响机理研究不同,本文给出了一个通过表面电荷调节反应面位置的实例.
基金
国家自然科学基金(21802170).
