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.