Unraveling Electron Structure and Reaction Mechanisms of Functionalized Nickel-Based Complexes for Efficient Hydrogen Evolution

Developing an advanced photocatalytic water-splitting system for hydrogen evolution reaction (HER) remains a challenge. Herein, a series of easily available pyridine-functionalized nickel-based photocatalysts with elaborate electronic structures were predicted by density functional theory (DFT). The results indicated that the migration of photoinduced electrons could be significantly improved after functionalization of the photocatalysts, leading to a high performance for HER. Under the optimized conditions, as high as 1613.51 μmol of H₂ can be produced over 25 mg of Ni­(dpi)­(pys)₂ (dpi = 2,2′-dipyridyl) (pys = 2-mercaptopyridine) (PNSP 1) after irradiation for 3 h, corresponding to a turnover number (TON) of 5470. The reaction mechanism was further explored by experimental and DFT calculation results. The outstanding HER performance is primarily associated with a high photoelectron transfer rate, a weak binding energy between the photocatalyst and hydrogen molecules, and enhanced active sites for HER, which might benefit the reduction of the energy barrier of HER intermediates, ultimately boosting the performance for HER. This report on the use of DFT to predict molecular complexes with high-efficiency catalytic properties affords significant insights for the design of new and inexpensive photocatalysts.