A dual-functional integrated Ni₅P₄/g-C₃N₄ S-scheme heterojunction for high performance synchronous photocatalytic hydrogen evolution and multi-contaminant removal with a waste-to-energy conversion

With a goal of waste-to-energy conversion, herein we report synchronous hydrogen evolution and pollutant degradation via photocatalysis utilizing novel Ni₅P₄/g-C₃N₄ S-scheme (Step scheme) heterojunction. The 25 %Ni₅P₄/g-C₃N₄ (25NP/CN) sample generates 40.1 mmol g^-1h^-1hydrogen evolution and 94.4 % carbamazepine degradation simultaneously under visible light and anaerobic conditions. Furthermore, the hydrogen evolution with carbamazepine, bisphenol A, sulfamethoxazole and rhodamine B is manifolds higher than in water. From The in-situ XPS results confirm the S-scheme transfer between Ni₅P₄ and g-C₃N_4. The presence of Ni⁰@Ni₅P₄ where strong covalent interactions between Ni⁰ and Ni-P single layers on Ni₅-P₄ not only enhanced the visible absorption, charge transfer but also leads to hydrogen formation by H⁺ transfer via a cyclic intermediate in a co-ordinate complex of degradation intermediates with Ni. This route is in addition to obvious e^-/H⁺. The CBZ degradation and hydrogen evolution in aerobic/oxic conditions was also studied and 25NP/CN performs well under this atmosphere, inferring that oxidised intermediates act as electron donors and maintains the H₂ evolution in longer run too. The photogenerated holes directly oxidized the pollutant in addition to ^[rad]OH radicals in anoxic medium and separated/accumulated electrons leads to hydrogen evolution. The scavenging experiments reveal that photogenerated holes directly oxidized the pollutant in addition to ^[rad]OH radicals in anoxic medium and separated/accumulated high potential electrons (via S-scheme transfer) leads to hydrogen evolution. The clean energy production and pollutant mineralization are synchronously achieved. Henceforth, a waste-to-energy route is proposed by coupling photocatalytic hydrogen evolution to environmental restoration.