甲酸/甲酸盐催化分解制氢及其逆反应的第一性原理研究

Formic acid is environmentally friend, nontoxic, and easy to store and transport. Its decomposition can release hydrogen, and thus can be used as a potential high-energy-density hydrogen storage material. CO2 is an important greenhouse gas and formic acid is one of its hydrogenation products. In addition, formic acid and formate are important intermediates in the synthesis of methanol from CO2 hydrogenation, water-gas shift/reverse water-gas shift, and F-T reactions. Nowadays, energy resources are quickly becoming shortage and the protection on environment is becoming more severe. Therefore studies on the two coupled reactions, the catalytic decomposition of formic acid/formate and their catalytic synthesis, have being drawn intensive attentions. In order to design more powerful catalysis for the two coupled reactions, it is very important to carry systematic theoretical studies on the mechanisms of the two reactions. In the current project, this two coupled reactions will be systematically studied by first principle calculations. The nature of the catalytic centers and the influences of various factors, such as the size of the metal clusters, the exposed metal surfaces, the interaction between support and the catalysis, the ligands, the solvent, and the pH of the solution etc., on the catalytic performances of the catalysis will be studied in detail. The aim of this project is to provide new insights for the molecular design of highly active and selective catalysis for the two coupled reactions.

甲酸具有环境友好，无毒，易于储存和运输的特点。它分解可以得到清洁能源氢气，因此可以被作为高能量密度的储氢载体。CO2是一个重要的温室气体，它加氢可以生成甲酸。甲酸/甲酸根也是CO2加氢合成甲醇，水煤气/逆水煤气变换，以及F-T反应中的重要中间体。因此从理论上对甲酸/甲酸盐的分解及其合成进行系统研究，对这些反应的机理以及影响催化剂活性选择性的内在原因进行探索，最终指导实验设计更高效的催化剂，这在能源日趋紧张，环境要求日趋严厉的今天在基础和应用两方面都具有非常重要的意义。本项目拟采用第一性原理计算，对甲酸/甲酸盐分解制氢气及其CO2加氢合成这一对重要的催化反应循环进行系统研究，深入研究其反应机理以及催化反应活性中心的本质，探索金属团簇大小，金属晶面，载体催化剂相互作用，配体性质，溶剂种类，溶液酸碱性等对催化剂反应性能的影响，为设计新型高效的催化剂提供理论依据和指导。

本课题采用第一性原理计算方法，对金属表面和氧化物表面的甲酸分解/合成机理进行了系统研究，发现不同的表面甲酸分解机理很不相同，比如在Au表面甲酸主要分解生成氢气和CO2，而在Pd和Ga2O3表面则主要分解生成CO和水。我们还发现反应条件如温度对反应机理具有很强的影响，比如在低温下Pd分解甲酸的中心主要是PdCO，而在高温则是Pd原子；Ga2O3表面则在低温会生成CO2和水，而在高温下原位生成的表面O空穴则催化甲酸分解生成CO+H2O。我们还拓展了甲酸催化体系，研究了非金属路易斯酸碱对活化甲酸的机理。本研究对甲酸分解机理的系统研究，为实验设计高效的甲酸分解催化剂提供了理论指导和依据，并为后续的研究奠定了坚实基础和开拓了新的研究方向。本课题初步完成了项目预定目标，在发表SCI论文方面甚至超额完成了预定的任务，共计发表SCI论文18篇。