Fabrication of P-doped Co9S8/g-C3N4 heterojunction for excellent photocatalytic hydrogen evolution

Developing lower-cost and higher-efficient photocatalysts is still a major challenge for the solar to hydrogen energy conversion by photocatalytic water splitting. Herein, P-doped Co₉S₈ (P–Co₉S₈) was synthesized by a hydrothermal process using low-cost RP as raw material, and then P–Co₉S₈ was employed to construct heterojunction with g-C₃N₄ via a mechanical-mixing method. Investigation shows that P–Co₉S₈ can not only improve the electrical conductivity and surface area of the composite, but also can lower the over-potential of H₂ evolution, leading to an enhanced H₂ evolution kinetics. The H₂ evolution rate of resultant 25% P–Co₉S₈/g-C₃N₄ reached 4362 μmol g^?1 h^?1 under UV and visible light, being nearly 121.2 times higher than that of g-C₃N₄. The charge transfer between P–Co₉S₈ and g-C₃N₄ follows the Type-I route based on the photoelectrochemical analysis, leading to more electrons on the conduction band of P–Co₉S₈ to participate the H₂ evolution processes. This work provides a new way for preparation of P-doped sulfides with potential applications in the field of photocatalysis.