MNxO4-x作为ORR/OER活性位点的电催化性能研究

The Electrocatalytic Performance Study of MNxO4-x as Active Sites for ORR/OER

摘要:

目前开发双功能电催化剂是解决金属-空气电池和燃料电池氧电极电化学过程缓慢及能量转化效率低等问题的重要手段之一，其中负载过渡金属单原子的氮掺杂石墨烯材料（M-N-C）被认为是最有希望替代贵金属的催化材料。研究表明M-N-C催化剂的高活性归因于其中过渡金属-氮氧配合物（MNxO4-x）的存在，为了探究MNxO4-x配位结构对材料催化性能的影响，本文基于第一性原理，通过在Fe-N-C材料中引入氧构建不同的FeNxO4-x（x = 0, 1, 2, 3, 4）配合物，研究金属原子的配位数x对氧还原反应（ORR）和氧析出反应（OER）催化性能的影响。结果表明，具有FeN4配位结构的Fe-N-C材料热力学稳定性及ORR/OER催化性能最佳。此外，本文通过变换过渡金属的种类，即锰、铁、钴、镍、铜（M=Mn、Fe、Co、Ni、Cu），研究过渡金属的种类M对MN4催化活性的影响。研究发现，具有CoN4配位结构的M-N-C材料热力学稳定，且相较于其他MN4其ORR和OER催化性能最佳。本论文的研究结果可为调节过渡金属单原子的配位环境，设计高效双功能电催化剂提供理论参考。

Abstract:

At present, developing bifunctional electrocatalysts plays an important role in the field of metal-air batteries and fuel cells. Non-noble transition metal single atoms loaded on the nitrogen-doped graphene sheets (M-N-C) are considered to be the most promising materials to replace noble metal electrocatalysts owing to the metal coordination compounds (MNxO4-x) in M-N-C with high catalytic activity. In this work, oxygen atoms were introduced in Fe-N-C to construct FeNxO4-x (x = 0, 1, 2, 3, 4) for studying the effect of coordination number x on the catalytic performance of ORR/OER. It was found that Fe-N-C showed the best thermodynamic stability and catalytic activity when x = 4. In addition, the effect of transition metal type was studied by introducing different transition metals, such as M = Mn, Fe, Co, Ni, Cu, in MN4. Among them, the thermodynamically stable CoN4 structure was the best choice for M-N-C to reach the highest ORR/OER catalytic activity. It is expected that this paper could provide a theoretical reference for adjusting the coordination environment of transition metal single atoms and designing high efficient bifunctional electrocatalysts.