In-Situ Deposition of Red Phosphorus onto BN: A Metal-Free Heterojunction for Efficient Photocatalytic Pure Water Splitting to Produce H ₂ and H ₂ O ₂

Developing metal-free photocatalysts for solar-driven pure water splitting to simultaneously produce H2 and H2O2 is an environmentally friendly ideal approach. Hexagonal boron nitride (BN), with high chemical and thermal stability, is a promising nonmetallic photocatalyst. However, its wide bandgap (5 ∼ 6 eV) results in extremely low photocatalytic efficiency. This work developed a method for promoting the decomposition of PH3 by boron species (BH3) to achieve the in situ deposition of red phosphorus (Red P) on BN, thereby constructing a nonmetal heterojunction. In the B-Red P/BN heterojunction, Red P, due to its narrow bandgap (1.5 ∼ 2.1 eV), can be excited by visible light to generate electron–hole pairs. Meanwhile, the electronegative BN acts as an effective hole extractor, enhancing the separation of charge carriers on the Red P surface and reducing the probability of holes being captured and recombined with electrons. Therefore, the B-Red P/BN heterojunction exhibits good visible light photocatalytic activity for pure water splitting to simultaneously produce H2 (212.5 μmol h–1 g–1) and H2O2 (172.0 μmol h–1 g–1) without any sacrificial agent. The methods described in this paper can also be extended to the construction of other Red P-based nonmetallic composites for photocatalysis.