Bimetal selenide NiSe/ZnSe heterostructured nanoparticals decorated porous g-C3N4 nanosheets to boost H2 evolution and urea synthesis

• Heterostructured NiSe/ZnSe nanoparticles were prepared by one-step selenization. • NiSe/ZnSe/g-C 3 N 4 shows superior photocatalytic performance compared to g-C 3 N 4 . • NiSe/ZnSe heterojunction plays two important roles - constructing heterojunction and cocatalyst. • The synergistic effect of heterojunction and cocatalyst is more conducive to the separation and transfer of photocarries. Promoting the separation and transfer of photocarries is very critical in designing an effective photocatalyst. In this study, a novel bimetal selenide Zn x Ni 1−x Se with NiSe/ZnSe heterostructure prepared by one-step selenization to construct ternary catalytic system NiSe/ZnSe/g-C 3 N 4 (Zn x Ni 1−x Se/g-C 3 N 4 ). Consequently, the photocatalytic activity of Zn x Ni 1−x Se/g-C 3 N 4 is greatly enhanced and higher than that of binary ZnSe/g-C 3 N 4 or NiSe/g-C 3 N 4 . The hydrogen production rate of 7 % Zn 0.7 Ni 0.3 Se/g-C 3 N 4 reaches 410.15 μmol h −1 g −1 , which is 34 times of pure g-C 3 N 4 and 1.5 times of 1 % Pt/g-C 3 N 4 . For urea synthesis, 10 % Zn 0.7 Ni 0.3 Se/g-C 3 N 4 show the highest urea synthesis rate of 1.12 μmol h −1 g −1 , which is about 6 times of pure g-C 3 N 4 . The intrinsic mechanism analysis indicates that bimetal selenide NiSe/ZnSe heterojunction plays two roles in Zn x Ni 1−x Se/g-C 3 N 4 system. Both ZnSe and g-C 3 N 4 forms a type II heterojunction to effectively separate photocarriers. Meanwhile, NiSe provides hydrogen evolution active sites due to its smaller H adsorption free energy, making hydrogen more easily generated and released on it. The synergistic effect of ZnSe/g-C 3 N 4 type II heterojunction and NiSe co-catalyst is more conducive to the separation and transfer of photocarries, thereby resulting in a remarkably enhanced activity. This work provides a unique construction method to design an effective ternary photocatalysts with a double stimulative effect.