Constructing low-cost Ni₃C/twin-crystal Zn_0.5Cd_0.5S heterojunction/homojunction nanohybrids for efficient photocatalytic H₂ evolution

The development of low-cost semiconductor photocatalysts for highly efficient and durable photocatalytic H₂ evolution under visible light is very challenging. In this study, we combine low-cost metallic Ni₃C cocatalysts with twin nanocrystal Zn_0.5Cd_0.5S (ZCS) solid solution homojunctions for an efficient visible-light-driven H₂ production by a simple approach. As-synthesized Zn_0.5Cd_0.5S-1% Ni₃C (ZCS-1) heterojunction/homojunction nanohybrid exhibited the highest photocatalytic H₂-evolution rate of 783 μmol h^-1 under visible light, which is 2.88 times higher than that of pristine twin nanocrystal ZCS solid solution. The apparent quantum efficiencies of ZCS and ZCS-1 are measured to be 6.13% and 19.25% at 420 nm, respectively. Specifically, the homojunctions between the zinc blende and wurtzite segments in twin nanocrystal ZCS solid solution can significantly improve the light absorption and separation of photogenerated electron-hole pairs. Furthermore, the heterojunction between ZCS and metallic Ni₃C NP cocatalysts can efficiently trap excited electrons from ZCS solid solution and enhance the H₂-evolution kinetics at the surface for improving catalytic activity. This study demonstrates a unique one-step strategy for constructing heterojunction/homojunction hybrid nanostructures for a more efficient photocatalytic H₂ evolution compared to other noble metal photocatalytic systems.