Enhancing Photocatalytic Water Splitting for H2 Production Over Znln2S4 Photocatalysts by Forming Heterostructure

Abstract

Using solar energy for H₂ production by photocatalytic water splitting is considered a green approach to replace heavily polluted steam methane reforming. Upon certain modification, Znln₂S₄ (ZIS) has been considered as a promising candidate for H₂ production via water splitting. In this study, non-metal doping and the formation of heterostructure were applied to synthesize Mo₂C (MC)/ZIS heterosystem and N-ZIS. Their H₂ evolution via water splitting was compared with TiO₂. After determining the optimal photocatalyst, both generations of total gases and individual gases (i.e., H₂ and CO₂) were maximized by studying different reaction conditions (i.e., photocatalyst concentration and type and dosage of sacrificial agent). Finally, the stability of the best photocatalyst at the optimal H₂ production conditions was investigated. Results show that the MC/ZIS was identified as the best photocatalyst. The optimal reaction conditions were determined to be: photocatalyst concentration of 0.015 wt%, methanol as the sacrificial agent, 20 vol% methanol dosage for 2 h reaction time, producing the highest evolution of total gases of 22,024 µmol/g_catalyst. It was also observed that the highest amount of H₂ evolution was obtained at 990 µmol/g_catalyst at 0.104 wt% concentration of photocatalyst and using 20 vol% methanol as a sacrificial agent for 2 h. For the stability of MC/ZIS, there were no considerable changes in the first two cycles. However, the amount of H₂ evolution was reduced by 26.78% after 3rd cycle. Overall, this study provides new insights into H₂ production via photocatalytic water splitting can be enhanced by forming a heterojunction system.

Graphical Abstract