Selective deposition of cocatalyst NiS on a g-C3N4/ZnIn2S4 heterojunction for exceptional photocatalytic H2 evolution

Abstract

Photocatalytic H₂ generation has long been supposed to be an intriguing approach for obtaining clean energy, but it is challenging to achieve a satisfactory efficiency mainly restricted by the high recombination rate of photoexcited carriers. The designing of a directional channel for the spatial separation of photogenerated electrons and holes to different components may be an ideal solution. To prove this point, a ternary hybrid g-C₃N₄/ZnIn₂S₄/NiS, in which NiS is directionally anchored onto ZnIn₂S₄, is successfully synthesized according to the Fajans rule. Compared with single g-C₃N₄, ZnIn₂S₄ and the counterpart in which NiS is randomly deposited onto g-C₃N₄/ZnIn₂S₄, the designed g-C₃N₄/ZnIn₂S₄/NiS exhibits the highest photocatalytic activity, with an H₂ evolution rate of 16310 μmol g⁻¹. The mechanism research showed that the matched band structure and interfacial electric field oriented from ZnIn₂S₄ to g-C₃N₄ facilitate the photo-induced electron transfer from g-C₃N₄ to ZnIn₂S₄. NiS nanoparticles that attached to ZnIn₂S₄ can act as electron trappers, thus further promoting the electron-hole separation efficiency. This work sheds light on the rational design and synthesis of heterojunctions for photocatalytic applications.