Photocatalytic H2 evolution over MnCoSe2 decorated red phosphorus with S-scheme charge transfer route

The improvement of charge separation and utilization efficiency plays a vital role in attaining efficient photocatalytic conversion processes. In this study, MnCoSe₂/RP heterojunctions were synthesized using the hydrothermal method and solvent evaporation method. The investigation indicates that the H₂ evolution rate (r_H2) of 3 wt% MnCoSe₂/RP can reach up to 2223.9 μmol·g⁻¹·h⁻¹ in 0.35 M Na₂S/0.25 M Na₂SO₃ solution, which is 9.3 and 19.5 times higher than those of the RP (214.8 μmol·g⁻¹·h⁻¹) and MnCoSe₂ (108.4 μmol·g⁻¹·h⁻¹), respectively, as well as better than that of 3 wt% MnSe₂/RP and 3 wt% CoSe₂/RP prepared under similar conditions. This enhancement is ascribed to the synergistic promoting effect exerted by Co and Mn, leading to fast photoelectric response, low charge transfer resistance, efficient electron-hole separation capability, and suitable H₂ evolution overpotential. Besides, it is found that the charge transfer between MnCoSe₂ and RP follow S-scheme route, which can maintain the active electrons and holes with good redox properties. Furthermore, the r_H2 can be further improved by adding appropriate amount of (NH₄)₂HPO₄, which can induce more H⁺ for H₂ evolution by HPO₄⁻ dissociation. Overall, this work shows that transition metal selenide can be a good candidate to form RP-based S-scheme photocatalyst for solar photocatalysis.