在电化学氮还原(NRR)合成氨过程中,为了认识真实水环境对过渡金属掺杂氮碳材料催化NRR活性的影响,并筛选出实际催化性能最佳的构型,本研究通过密度泛函理论(DFT)和从头算分子动力学(AIMD)相结合的方法,对一系列不同配位形式的过渡金属掺杂氮碳催化剂(TMN_(x)C_(y), TM=Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn;x=1~4;y=4-x,总共40种构型)催化NRR的热力学稳定性和实际氮还原催化活性进行了系统研究.计算结果表明,本工作所研究的40种催化剂结构均具有较高的热力学稳定性,可作为实际的NRR候选催化剂.其中,利用隐性+显性水溶剂模拟真实水环境时,过渡金属V掺杂形成的VN3C1结构催化NRR酶机制过程的最大吉布斯自由能变值仅为0.35eV(在U=0 V vs. RHE时),表现出最佳的NRR催化性能.总体而言,本研究采用DFT与AIMD相结合的方法,深入地阐述了TMN_(x)C_(y)催化剂的实际NRR催化过程,为实验过程做出了更为贴切的理论预测.
Developing highly active bifunctional electrocatalysts for oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)is of great significance in energy conversion and storage technologies.In this study,we systematically investigated the OER/ORR electrocatalytic activity of TMN_(4)@G system by using density functional theory(DFT)calculations.Globally,IrN_(4)@G is a very promising bifunctional catalyst for both OER and ORR with the extremely low overpotentials of 0.30 and 0.26 V,respectively.Such outstanding electrocatalytic performance is mainly attributed to the synergistic effect of Ir and N.More importantly,by constructing 2D activity volcano plots,we obtained the limiting overpotentials of TMN_(4)@G system with the values of 0.26 V for OER and 0.24 V for ORR.These findings open up new opportunities for further exploring graphene-based materials for highly efficient OER/ORR electrocatalysts.
