Theoretical Study On Hydrogen Peroxide Catalysis Of Carbon Based Monoatomic Catalysts

Hydrogen peroxide（H₂O₂）is a versatile oxidant with various industrial applications,including energy storage,pulp bleaching,chemical synthesis,and water treatment.Traditional methods for H₂O₂ synthesis,such as the Riedl-Pfleiderer process,are costly and require the use of toxic auxiliaries,making them environmentally unfriendly.In recent years,electrochemical methods have shown great promise for the green synthesis of H₂O₂ production,but most of the catalysts used for H₂O₂ production are precious metals or precious metal-based alloys,which are not only scarce but even toxic.Single-atom catalysts（SACs）have emerged as promising alternatives to noble metal catalysts and can be enhanced by appropriate supports.Graphene-like carbon nitride（g-C₃N₄）and graphyne（γ-GY）are two popular two-dimensional carbon-based materials that have recently been widely applied in electrocatalysis research due to their unique electronic and geometric properties.However,the current primitive carbon materials exhibit poor selectivity and activity for2e^-ORR.In this paper,first-principles calculations will be conducted to form carbon-based single-atom catalysts by studying the transition metal atoms loaded on g-C₃N₄ andγ-GY.The high-performance 2e^-ORR catalysts with high activity,selectivity,and stability will be screened.This provides a theoretical basis for the design and preparation high-performance catalysts.The main research content and innovative points are as follows:First,we employed density functional theory to construct transition metal single-atom catalysts supported on g-C₃N₄,and investigated their 2e^-ORR electrocatalytic activity and the influence of their electronic structure in this study.We then carried out electronic structure characterization analyses,including partial density of states（PDOS）,differential charge,and bader charge,for the lowest overpotential Ag@g-C₃N₄.The 2e^-ORR catalytic mechanism of Ag@g-C₃N₄ is attributed to the strong hybridization between the 4d orbitals of Ag and the 2p orbitals of O,which provides appropriate adsorption strength for O₂ molecules and intermediate OOH*species on Ag@g-C₃N_4。In order to simulate the catalytic performance of Ag@g-C₃N₄in real environment,we have calculated the model of explicit solvent.Although the overpotential of Ag@g-C₃N₄ was slightly increased,the two-electron pathway was still the preferred pathwaySecond,we constructed TM@γ-GY single-atom catalysts and used a three-step screening strategy to quickly identify five catalysts（Ag,Cu,Ni,Pd,Pt）@γ-GY.However,we found that these five catalysts exhibited extremely weak adsorption capacity for O₂.We then studied the modification of the catalysts by constructing carbon defects and doping with B and N atoms,and screened out two highly efficient catalysts.Cu@V-γ-GY and Ni@B-γ-GY,with overpotentials of 0.03 V and 0.08 V,respectively.We investigated the process of O₂ adsorption on the surfaces of Cu@V-γ-GY and Ni@B-γ-GY from several aspects,including differential charge density,bader charge,PDOS,and COHP.We found that carbon defects and B atom doping altered the coordination environment of Cu and Ni atoms,strengthening the hybridization for 3d orbitals of Cu/Ni with 2p orbital of O.This is the origin of the high 2e^-ORR catalytic activity exhibited by Cu@V-γ-GY and Ni@B-γ-GY.The results of this paper explain well the performance of these two systems in catalyzing hydrogen peroxide,and also predict that Cu@V-γ-GY and Ni@B-γ-GY have excellent catalytic ability,hoping to provide theoretical information for the optimization of catalysts in industrial production of hydrogen peroxide and the direct application of catalysts.