超低铂表面氧的还原和甲醇氧化电催化活性差异的机理

The development of low-platinum cathode catalyst with high performance has become a general interest in the field of direct methanol fuel cell (DMFC). The difference in electro-catalytic activity between oxygen reduction and methanol oxidation on the ultra-low platinum catalyst surface is a new phenomenon recently founded by the applicant in experiment. The study on the mechanism for the difference by the methods of quantum chemistry calculation and in-situ spectroscopy will provide the fundamentals of new-generation DMFC technology. In this project,we will investigate the formation and transformation of intermediates during oxygen reduction and methanol oxidation reaction by in-situ FTIR technique, calculate adsorption energy and activation energy by density function theory, and reveal the mechanism for the activity difference between the two electro-catalytic reactions on the surface of ultra-low amount of platinum. Based on the synergistic effects of ultra-low Pt, heteroatoms-doped carbon carriers and non-platinum nanoparticle core, we will further design and prepare ultra-low platinum content cathode catalysts with high activity in acid media. The results will provide the basically technological support for the large-scale commercialization of proton exchange membrane DMFC in the short term.

开发高性能低铂直接甲醇燃料电池（DMFC）阴极催化剂是DMFC研究领域中国内外学者共同关注的热点。超低铂表面氧的还原和甲醇氧化电催化活性存在差异是近期实验中发现的新现象。通过原位光谱实验和量子化学理论计算研究该差异的机理可望为开发新一代DMFC阴极活性催化剂奠定理论基础。本项目采用原位红外光谱实时监测超低量铂表面氧的还原和甲醇氧化过程，根据获取的中间过渡物种的红外光谱信息，利用量子化学的密度泛函理论等手段计算氧分子与甲醇分子在超低铂表面上吸附能及反应活化能等参数，揭示超低铂表面两电催化反应的活性差异机制。在此基础上，借助超低铂催化剂与在酸性条件下具有氧还原活性的掺杂型碳载体之间及与具有氧还原活性的非铂催化剂纳米粒子核之间的协同效应，设计开发出与质子交换膜成熟技术相适应的高性能DMFC超低铂阴极催化剂，为短期内推动酸性DMFC商业化提供技术支撑。

为揭示本项目少量铂催化剂表面氧还原和甲醇氧化电催化活性的差异原因，实验上通过在碳载体上负载不同质量铂催化剂并分别考察其氧还原和甲醇氧化的电催化性能变化规律，结果表明质量传输和质子传递分别是铂催化剂表面氧还原和甲醇氧化电催化反应的控制因素，活性位和碳载体之间相互作用直接影响氧还原峰电位，而甲醇氧化电位则主要铂催化剂晶面的本证特性决定。同时实验和理论计算表明杂原子掺杂碳载体可增加铂原子的电子密度及与载体之间吸附能而提高铂催化剂的氧还原活性和稳定性；硅、砷和锗等杂原子也可掺入碳的网络结构而提高碳载体本身的氧还原活性。此外实验表明煤焦油、生物质和废弃塑料等廉价原料可用作杂原子前驱物制备本身具有较好氧还原活性的碳载体。以上实验与理论研究成果可望为高活性低成本的甲醇燃料电池阴极催化剂的规模化开发提供技术支撑。