Au/g-C3N4 heterostructure sensitized by black phosphorus for full solar spectrum waste-to-hydrogen conversion

Abstract

Photocatalytic water splitting with simultaneous degradation of organic pollutants is an effective strategy to alleviate the increasingly serious energy and environmental crisis. However, the photocatalytic activity is restricted by the high charge recombination rate and limited sunlight utilization. Herein, black phosphorus (BP) with a broad sunlight response range was utilized as a photosensitizer to enhance the photocatalytic performance of the Au/carbon nitride (CN) heterostructure. The as-prepared BP/Au/CN exhibited a significantly enhanced H2 generation rate of 1400.8 µmol h−1 g−1 under UV-vis light irradiation, which is almost 70 times higher than that of bare CN and BP/CN and 2 folds higher than that of the Au/CN heterojunction. Specifically, the optimal BP/Au/CN sample presented a waste-to-hydrogen production rate of 195.8 µmol h−1 g−1 with the degradation of bisphenol A, verifying the synergistic effect of the ternary heterojunction. The photocatalytic mechanism was systematically studied by the combination of experiments and theoretical calculations. The improved photocatalytic performance was derived from the overall sunlight absorption ability of BP, effective electron transfer media and plasmonic character of Au nanoparticles, as well as the matched work function and strong interaction of the three components. A unidirectional electron transfer from BP to Au and then to CN was established, which effectively improved the charge transfer capability, resulting from the appropriate Ohmic contact of Au and BP and the Schottky barrier constructed in Au/CN hybrid.