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

Abstract

Promoting the separation and transfer of photocarries is very critical in designing an effective photocatalyst. In this study, a novel bimetal selenide ZnxNi1−xSe with NiSe/ZnSe heterostructure prepared by one-step selenization to construct ternary catalytic system NiSe/ZnSe/g-C3N4 (ZnxNi1−xSe/g-C3N4). Consequently, the photocatalytic activity of ZnxNi1−xSe/g-C3N4 is greatly enhanced and higher than that of binary ZnSe/g-C3N4 or NiSe/g-C3N4. The hydrogen production rate of 7 % Zn0.7Ni0.3Se/g-C3N4 reaches 410.15 μmol h−1 g−1, which is 34 times of pure g-C3N4 and 1.5 times of 1 % Pt/g-C3N4. For urea synthesis, 10 % Zn0.7Ni0.3Se/g-C3N4 show the highest urea synthesis rate of 1.12 μmol h−1 g−1, which is about 6 times of pure g-C3N4. The intrinsic mechanism analysis indicates that bimetal selenide NiSe/ZnSe heterojunction plays two roles in ZnxNi1−xSe/g-C3N4 system. Both ZnSe and g-C3N4 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-C3N4 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.