Revealing the Origin of Graphene Anchored Single Palladium Atom for Electrochemical CO2 Reduction to Syngas with Tunable CO/H2 Ratios

Abstract Pd based catalysts are rare metal‐based catalyst to yield tunable CO/H 2 ratios for Fischer‐Tropsch synthesis. How to achieve the co‐production of CO and H 2 with as little Pd as possible is extremely meaningful for C n industry. Recent experiment revealed single Pd atom anchored on graphene exhibits high activity for CO 2 electroreduction to syngas, yet the origin of activity and controllable CO/H 2 ratios, especially the exact Pd coordination structure, remains elusive. Here we employ grand‐canonical density functional theory to show that Pd−N 1 , rather than the commonly accepted Pd‐N 4 , serves as the active center, and the charge‐carrying capability is an effective descriptor. The site with more Pd−C coordination can better submerge in graphene‘s delocalized π electrons for higher charge‐carrying capacity to carry excess charges that occupy Pd 4d z 2 orbital and promote electron injection. Importantly, the tunable CO/H 2 ratio can be explained with difference in charge‐carrying capability of transition state for *COOH and *H 2 formation. This work solves the puzzle of coordinating structure of Pd active site and demonstrates the important role of charge‐carrying capability in electrochemical process, which shall provide a reference for further exploration of efficient electrocatalysts.