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 (rH2) of 3 wt% MnCoSe2/RP can reach up to 2223.9 mu mol center dot g- 1 center dot 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 mu mol center dot g-1 center dot h-1) and MnCoSe2 (108.4 mu mol center dot g-1 center dot 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 rH2 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 RPbased S-scheme photocatalyst for solar photocatalysis.