Molybdenum sulfide-modified metal-free graphitic carbon nitride/black phosphorus photocatalyst synthesized via high-energy ball-milling for efficient hydrogen evolution and hexavalent chromium reduction.

Improving the photocatalytic property of metal-free photocatalyst is still a challenging work. Herein, a novel high-efficiency molybdenum sulfide (MoS)-modified metal-free graphitic carbon nitride (g-CN)/black phosphorus (BP) photocatalyst (MCN/BP/MS) was synthesized on a large scale via high-energy ball milling process. The optimized MCN/BP/MS exhibits the excellent hydrogen evolution rate of 2146.8 µmol·g·h, and hexavalent chromium (Cr(Ⅵ)) reduction activity with an apparent rate constant of 0.1464 min and a degradation rate of 100% in 25 min. Detailed characterizations and mechanism research verified that the significantly improved photocatalytic activity of MCN/BP/MS mainly profited from the matched band structure, enhanced light absorption, intense interface contact, as well as the type-Ⅰ/Z hybrid charge transfer mechanism, which gave rise to a consecutive multistep charge migration, thus the photocarriers transfer and separation can be greatly promoted, and the photogenerated electrons with high reducing capacity can be preserved. This work not only provides a high-efficiency g-CN-based noble-metal-free photocatalyst, but also affords a beneficial inspiration for improving the photocatalytic property of the metal free photocatalyst.