Constructing sewage waste sludge supported ZnCo2S4 with 1D g-CNNR S-scheme ZnCo2S4/g-CNNRs/SWS heterojunction with efficient charge separation through metallic elements for stimulating photocatalytic H2 production

Well-designed sewage-waste-sludge (SWS) derived metallic elements to construct novel S-scheme ZnCo 2 S 4 /g-CNNRs heterojunctions for photocatalytic hydrogen production have been investigated. The role of SWS as a mediator with the influential effect of metal elements (M = Ni, Cu, Fe, and Mn) for higher charge separation and utilization were explored. The pure SWS was found promising to work as a support and co-catalyst, enabling 25 μmol g −1 h −1 of H 2 production due to the presence of metal oxides activated under visible light. Altering g-C 3 N 4 structure to 1D g-C 3 N 4 nanorods (g-CNNRs) and coupling with SWS stimulated H 2 production to 195 μmol g −1 h −1 due to efficient charge separation and transfer. Constructing S-scheme heterojunction of ZnCo 2 S 4 /g-CNNR/SWS enabled 393 μmol g −1 h −1 of H 2 , which is 9.14 and 15.72 folds higher than using g-CNNRs and SWS, respectively. The significant enhancement in photocatalytic efficiency was due to maximizing redox potential with a larger exposed surface, higher visible light utilization and synergetic effects of SWS elements for efficient charge carrier separation. The ternary composite assisted by SWS was also beneficial to maximize the stability for continuous H 2 production in multiple cycles. Thus, waste sludge with these structured materials can be used in developing low-cost catalysts and would be promising for other energy applications. • Sewage waste sludge (SWS)-based composite catalyst synthesized for H 2 production. • ZnCo 2 S 4 /g-CNNR/SWS has higher light absorbance and charge separation efficiency. • ZnCo 2 S 4 /g-CNNR/SWS produced highest H 2 yield due to S-scheme heterojunction. • High stability was obtained due to SWS with layered structures of ZnCo 2 S 4 /g-CNNR.