Electronic Structure Engineering in MXene SACs: Unveiling the Role of Mixed Termination for ORR/OER Bifunctionality

ABSTRACT Based on a pristine Ti ₂ CCl ₂ substrate with single functionalization, this study implemented precise electronic structure modulation to construct a series of Ti ₂ CO _X Cl _Y models, aiming to elucidate the origin of catalytic activity in MXenes with mixed functional groups of varying ratios. It was discovered that precisely tuning the relative content of O/Cl terminal groups on the Ti ₂ C substrate significantly optimizes the adsorption energy of the key intermediate OH ^* in both the oxygen reduction reaction and oxygen evolution reaction, thereby enabling superior bifunctional catalytic performance at the same active site. This work establishes a clear descriptor that clarifies the structure‐activity relationship in catalytic reactions from the unique perspective of mixed functional groups, providing new theoretical insights for designing high‐performance single‐atom catalysts.