高效非贵金属氧还原催化剂的理性构筑及催化机理的研究

We focus on the study on the rational design and the preparation of non-precious metal catalysts in oxygen reduction reaction (ORR), including cheap metal (Fe, Mn and Mg) and Si-doped non-metal catalysts. The possible catalytic active sites can be constructed at theoretical level to predict their activities, which can provide guidance of preparing ORR catalysts. For non-precious metal ones, the M-Nx (x=2, 4) structure and MxNy nanoparticle-type can be constructed, on the other hand, various Si-C and Si-N structures should be considered for Si-doped catalysts. We will investigate the effect of catalyst preparation parameters on the structures and performances of catalysts. Moreover, the combination of various experimental characterization methods (TEM, XRD, XPS and Raman spectra) with quantum chemical method has been performed to study the ORR mechanism. We will simulate the adsorbed intermediates on the surface of the catalysts, and the activation energies for elementary reaction. Then the possible reaction paths will be described. The catalytic active structures will be adjusted based on the theoretical calculations, which can be used to design new non-precious metal catalysts instead of commercial Pt/C ones. It will provide better theoretical foundation for promoting the performance of the non-precious metal catalysts.

本项目拟采用理论结合实验的手段对新型高效的铁、锰和镁等廉价金属和硅掺杂的非金属氧还原催化剂进行理性设计与控制制备。理论构建可能的催化活性位点结构（M-Nx活性位点以及MxNy纳米粒子结构位点，Si-C/N掺杂结构等），预测其催化活性，指导实验制备氧还原催化剂，并结合透射电镜、X-射线衍射、X-射线光电子能谱以及拉曼光谱能物理表征手段来详细考察制备参数对催化剂结构和性能的影响；通过实验结合量子化学理论方法深入研究所制备的催化剂的氧还原催化机理，模拟氧气在催化剂表面的吸附中间体以及反应的活化能，描述可能的反应路径；并根据理论模拟来调整催化剂的活性位点结构，设计更高性能的催化剂来替代商业碳载铂，为合理构筑高性能的非贵金属氧还原催化剂提供理论支持

在能源占主导地位的当今，燃料电池因其环境友好、寿命长等优点，备受关注。但因其阴极反应的氧还原过程速度慢，且交换电流密度低，成为制约燃料电池性能的制约步骤。而常规的商业铂碳催化剂成本高、易被毒化导致稳定性差的因素，严重制约了燃料电池商业化进展。因此发展高效廉价的非贵金属或非金属氧还原催化剂尤为重要。而对氧还原反应机理的深入剖析对催化剂的制备也会产生极大的促进作用，使实验更具目的性。而量子化学手段的引入预测氧还原反应机理可以为制备催化剂提供理论依据，缩减实验时间和成本。.理论预测方面，本文从量子化学角度出发，理论构建硅氮掺杂的碳材料结构位点，并预测硅氮相邻共掺杂时对氧还原催化性能最高，从而指导实验制备了高效的硅氮共掺杂非金属氧还原体系。在催化剂制备方面，基于廉价的铁、锌以及碳材料，通过简单的回流法制备了高性能高稳定性的铁基和单原子锌基氧还原催化剂。发现回流法可以产生小而均一的纳米粒子，保证了体系的稳定性。基于实验表征预测得到的初步结构，理论构建模型并对催化活性位点进行活性预测并解析催化反应机理，为构建新型高效廉价氧还原催化剂提供新思路。