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

Based on a pristine Ti₂CCl₂ substrate with single functionalization, this study implemented precise electronic structure modulation to construct a series of Ti₂CO_XCl_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 Ti₂C 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.