Computational Electrochemistry With Explicit Potential Method To Study Active Structures For Oxygen Reduction Reaction And Carbon Dioxide Reduction Reaction

Currently,various energy and environmental problems have promoted the rapid development of the research on electrochemical energy storage and transformation.However,the design and development of electrocatalysts for highly reactive energy conversion reactions requires a deep understanding of their active structures and the electrocatalytic processes.At present,computational electrochemical simulations based on“Density Functional Theory”（DFT）are the main method of obtaining these understandings.The“Computational Hydrogen Electrode”（CHE）method based on the electrical neutral model is widely used in the theoretical simulation of electrocatalysis due to its simplicity.But in recent years,it has been found that this method of implict potential consideration will produce large errors in 2D material models and lead to the misjudgment of active structures.In this study,we improve the CHE method by adding/removing electrons to match the work functions under different electrode potentials,and the electrode potential effect is explicitly introduced to make the simulation closer to the real electrochemical environment.Here,we studied the active structures of recently reported catalysts in two important electrochemical reactions for energy conversion（Oxygen Reduction Reaction（ORR）and Carbon Dioxide Reduction Reaction（CO₂RR））.（1）To solve the controversy on the highly active structures of Fe-N/C ORR electrocatalysts,we collected eleven proposed Fe-N/C ORR configurations,and compared their activities under the same electrode potentials for the first time.The results show that the Fe N₄ located at the carbon zigzag edge and decorated by OH ligand is the best one among all the proposed moieties.The detailed analysis shows that the edge-hosting and ligand-decoration can lower the d-band center of the Fe center to tune the adsorption of ORR intermediates,thus increasing the ORR activity.This study not only demonstrates the significance of electrode potential in the computational electrochemistry,but also suggests a feasible experimental strategy to increase the ORR performance of Fe-N/C electrocatalysts by creating edges defects and coordinating with axial the anion ligands,which is of practical significance for exploring the advanced nonprecious metal-based ORR electrocatalysts and related devices.（2）There are some studies demonstrate that the activity of metal-free P-N co-doping carbon materials can compete with the transition metal-based catalysts for CO₂RR.The previous theoretical studies all used the traditional CHE method,and believed that the active site was pyridine nitrogen or the ortho-carbon of P,and P only played the role of an electronic assistant.We used the modified CHE method with explicit potential to re-explore this kind of active structure.The results show that the electrode potential will change the structure of P based active sites.In the range of the potential of CO₂RR（-0.8 V～-0.4 V）,a new type of highly active structure P=O will be generated in situ,which can directly absorb CO₂ to complete efficient transformation.These results not only show the variation of the active structure with the electric potential,but also provide a new idea for the preparation of carbon-based metal-free CO₂RR,that is,using the precursor containing the P-N bond to create high-density P-N sites.