Axial Benzotriazole‐Coordinated Ni Single Atoms Enable Rapid Interfacial Electron Transfer for Efficient Photocatalytic Acetylene Semi‐Hydrogenation

ABSTRACT Photocatalytic semi‐hydrogenation of acetylene (C 2 H 2 ) to ethylene (C 2 H 4 ) often suffers from inefficient interfacial electron transfer from the photocatalysts to adsorbed C 2 H 2 . Here, we demonstrate that axial coordination of benzotriazole (BTA) to Ni single atoms in C 3 N 4 (BTA‐Ni SAs‐C 3 N 4 ) facilitates interfacial electron‐transfer processes. Femtosecond transient absorption spectroscopy, in situ transient surface photovoltage spectroscopy, in situ photochemical infrared spectroscopy, and theoretical simulations reveal that BTA‐coordinated Ni SAs serve as the centers for rapid electron transfer by upshifting the Ni d‐band center and strengthening the orbital overlap between Ni SA and adsorbed C 2 H 2 . Consequently, BTA‐Ni SAs‐C 3 N 4 achieves a very high C 2 H 4 production rate of 32.29 mmol g cat −1 h −1 with a C 2 H 4 selectivity of 97.6% under simulated solar irradiation, which is ∼4‐times higher than that for Ni SAs‐C 3 N 4 . The apparent quantum yield at 365 nm is up to 4.65%, superior to reported photocatalytic acetylene semi‐hydrogenation. This work highlights the importance of interfacial charge transfer in photocatalytic acetylene hydrogenation and provides a rational strategy for designing high‐performance photocatalysts.