Axial Benzotriazole-Coordinated Ni Single Atoms Enable Rapid Interfacial Electron Transfer for Efficient...

Photocatalytic semi-hydrogenation of acetylene (C₂H₂) to ethylene (C₂H₄) often suffers from inefficient interfacial electron transfer from the photocatalysts to adsorbed C₂H₂. Here, we demonstrate that axial coordination of benzotriazole (BTA) to Ni single atoms in C₃N₄ (BTA-Ni SAs-C₃N₄) 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 C₂H₂. Consequently, BTA-Ni SAs-C₃N₄ achieves a very high C₂H₄ production rate of 32.29 mmol g_cat ^-1 h^-1 with a C₂H₄ selectivity of 97.6% under simulated solar irradiation, which is ∼4-times higher than that for Ni SAs-C₃N₄. 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.