Pt基催化剂表面氢氧电催化反应的理论计算研究

发布时间：2018-09-09 17:27

【摘要】：氢氧电催化反应是氢能源体系的重要反应,其热力学和动力学直接影响水解制氢和燃料电池的能量效率和功率密度.过去十多年来,基于量子化学的理论计算在电催化剂设计及电催化反应机理研究中得到广泛应用.结合文献结果,本文介绍了近年来在Pt基催化剂表面氢、氧电催化反应理论计算研究中获得的结果和认识.在研究中重点对反应中间体吸附结构、覆盖度及其对反应路径和动力学的影响机制进行了分析.结果指出,反应中间体的吸附特性不仅会影响反应控制步骤的活化能,同时通过改变表面反应活性位的结构和数量影响表面反应速率.对火山顶点附近的Pt基催化剂,简单计算的吸附能不足以准确预测催化剂活性,必须考虑吸附质的覆盖度和吸附结构的影响.在此认识基础上,根据表面反应自由能及速率与关键中间体吸附能、覆盖度及电极电势的关系建立微观动力学模型,利用密度泛函理论计算获得关键吸附中间体在催化剂表面的电化学吸附等温线(吸附结构及覆盖度与电极电势的关系),确定反应活性位、反应路径和动力学,构建催化活性与吸附能的关系曲线,预测催化剂的表面结构及尺寸效应,并对一些重要实验结果进行解释.
[Abstract]:Hydrogen-oxygen electrocatalytic reaction is an important reaction in hydrogen energy system. Its thermodynamics and kinetics directly affect the energy efficiency and power density of hydrogen production and fuel cell. In the past decade, theoretical calculations based on quantum chemistry have been widely used in the design of electrocatalysts and the study of electrocatalytic reaction mechanism. Based on the results of literature, this paper introduces the results and understandings obtained in the theoretical calculation of surface hydrogen and oxygen electrocatalytic reactions of Pt catalysts in recent years. In the study, the adsorption structure, coverage and the mechanism of reaction path and kinetics of the reaction intermediates were analyzed. The results show that the adsorption characteristics of the reaction intermediates not only affect the activation energy of the reaction control steps, but also affect the surface reaction rate by changing the structure and quantity of the active sites of the surface reaction. For the Pt based catalyst near the peak of the volcano, the calculated adsorption energy is not enough to predict the activity of the catalyst accurately. The influence of the coverage of adsorbate and the adsorption structure must be considered. On the basis of this understanding, a micro kinetic model was established according to the relationship between the free energy and rate of surface reaction and the adsorption energy, coverage degree and electrode potential of the key intermediates. The electrochemical adsorption isotherms of the key adsorbed intermediates on the catalyst surface were obtained by using density functional theory (the relationship between the adsorption structure and the coverage degree and the electrode potential), and the reactive sites, reaction paths and kinetics were determined. The relationship curve between catalytic activity and adsorption energy was constructed, the surface structure and size effect of catalyst were predicted, and some important experimental results were explained.
【作者单位】：湖北省化学电源重点实验室武汉大学化学与分子科学学院;
【基金】：国家自然科学基金(编号:21673163,21073137) 国家重点基础研究发展计划(编号:2012CB932800)资助项目
【分类号】：O643.36

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