Direct Observation of Z-Scheme Route in Cu₃₁S₁₆/Zn_xCd_1-xS Heteronanoplates for Highly Efficient Photocatalytic Hydrogen Evolution

Although photocatalytic hydrogen production from water holds great potential as a renewable and sustainable energy alternative, the practical application of the technology demands cost-effective, simple photocatalytic systems with high efficiency in hydrogen evolution reaction (HER). Herein, the synthesis and characterization of Cu₃₁S₁₆/Zn_xCd_1-xS heterostructured nanoplates (Cu₃₁S₁₆/ZnCdS HNPs) as a high photocatalytic system are reported. The cost-effective, hierarchical structures are easily prepared using the Cu₃₁S₁₆ NPs as the seed by the epitaxial growth of the ZnCdS nanocrystals (NCs). The Cu₃₁S₁₆/ZnCdS without the noble metal cocatalyst exhibits a high HER rate of 61.7 mmol g⁻¹ h⁻¹, which is 8,014 and 17 times higher than that of Cu₃₁S₁₆ and ZnCdS, respectively, under visible light irradiation. The apparent quantum yield (AQY) of Cu₃₁S₁₆/ZnCdS reaches 67.9% at 400 nm with the highest value so far in the reported ZnCdS-based photocatalysts. The excellent activity and stability of the Cu₃₁S₁₆/ZnCdS are attributed to the formation of a strong internal electric field (IEF) and the Z-scheme pathway. The comprehensive experiments and theoretical calculations provide the direct evidences of the Z-scheme route. This work may offer a way for the design and development of efficient photocatalysts to achieve solar-to-chemical energy conversion at a practically useful level.