Light-assisted rapid preparation of a Ni/g-C3N4 magnetic composite for robust photocatalytic H2 evolution from water

The precise combination of graphitic carbon nitride (g-C3N4) and nickel compounds is greatly desirable for the development of robust and low-cost photocatalytic systems made of earth-abundant elements. Herein, a rapid light-assisted method is proposed to prepare effectively combined Ni/g-C3N4 composite photocatalysts. In this process, the Ni(0) was formed from the reduction of Ni(II) by photogenerated electrons and was loaded on the electron outlet points of g-C3N4 within 30 min; the ratio of Ni/g-C3N4 can be adjusted by changing the amount of nickel salt added. When the loaded Ni was 7.40 wt%, a high photocatalytic H2 production rate of 4318 μmol g−1 h−1 was obtained and no noticeable decrease in the photocatalytic H2 evolution rate was observed after four runs for 48 h in an aqueous triethanolamine solution. Furthermore, the Ni/g-C3N4 composite photocatalyst presented the ability for sunlight-driven H2 production of 4000 μmol g−1 h−1 under natural sunlight outdoors. In addition, the mechanism for the efficient and stable activity of the Ni/g-C3N4 hybrid photocatalyst was investigated in detail through photoelectrochemical experiments and steady-state photoluminescence spectra. It was found that Ni effectively prevented the recombination of the photogenerated electrons and holes of g-C3N4 and improved the H2 evolution activity.