A First Principles Study On Tuning The Coordination Environment Of Transition Metal Single-atom Catalysts

The conversion of pollutants and the development of new energy sources are important tools to solve the environmental pollution and energy crisis.The process will involve a variety of catalysts,and the improvement of catalytic efficiency of any catalyst will have a significant impact on the whole industry and society.Transition metal single-atom catalysts are currently a hot topic of research,and there is still much room for research on the structural performance modulation of single-atom catalysts.In this paper,we have used various modulation strategies to modify the ligand environment of various transition metal monatomic catalysts and obtained remarkable results.The work carried out in this paper is as follows:（1）The effect of Ga atom doping on the performance of Pd/CeO₂ monatomic catalyst system was investigated.The calculated results show that Ga doping significantly enhances the stability of Pd single-atom loading on the surface of CeO₂（111）.In addition,the oxygen vacancies readily generated near the Ga and Pd sites can activate the adsorbed oxygen molecules.Transition state calculations show that the doping of Ga significantly reduces the highest energy barrier during the CO oxidation reaction,which implies that the catalytic performance of the CO oxidation reaction is effectively enhanced.This study provides a new perspective for the modification of single-atom catalysts.（2）The effect of Fe-Se atoms on the synergistic coordination on the electrocatalytic performance was investigated.In this study,we replaced one N atom in the FeN₄ coordination with a Se atom,thus constructing Fe-Se atom pair synergistically coordinated Fe-SeN₃ monatomic catalysts,and investigated their ORR performance.The results show that FeSeN₃ with the synergistic coordination structure exhibits excellent bifunctional electrocatalytic performance with an OER overpotential of 0.47 V and an ORR overpotential of 0.87 V,which are much lower than those of FeN₄ and SeN₄ catalysts.The introduction of Se atoms can disrupt the symmetric electron distribution of FeN₄ by unconventional p-d orbital hybridization,thus modulating the electronic structure and microenvironment of Fe sites and optimizing the adsorption/desorption behavior between active sites and intermediates during the ORR/OER process.（3）The effect of carrier curvature on the electrocatalytic performance was investigated.A novel curved graphene model was constructed by compressing the lattice constant and bending the C-C bond.Single-atom catalysts based on bent graphene were obtained by doping pyridine nitrogen-coordinated Co,Ni or CoNi atoms on the bent graphene.The results show that curvature has a significant effect on the electronic structure and electrocatalytic performance of graphene and graphene-based single-atom catalysts.The catalytic performance and stability of graphene-based monatomic catalysts can be effectively tuned by adjusting the curvature of graphene,which provides theoretical guidance for the design of these materials.