An insight into the trifunctional roles of Cu2(OH)2CO3 cocatalyst in boosting the photocatalytic H2 evolution activity over Zn0.5Cd0.5S nanoparticles

The construction of efficient semiconductor/cocatalyst heterojunction is a promising strategy to promote the photocatalytic H₂-production efficiency from water reduction. Herein, a novel Cu₂(OH)₂CO₃/Zn_0.5Cd_0.5S heterojunction composite with superior photocatalytic H₂-generation activity and stability was prepared via a facile in situ synthetic route, in which Cu₂(OH)₂CO₃ served as cocatalyst stimulating the photocatalytic H₂-evolution performance of Zn_0.5Cd_0.5S. The Cu₂(OH)₂CO₃/Zn_0.5Cd_0.5S heterojunction photocatalyst containing 5 wt% of Cu₂(OH)₂CO₃ exhibited a prominent H₂-evolution efficiency of 275.7 μmol h⁻¹, which is superior to the noble metal Pt-modified Zn_0.5Cd_0.5S photocatalyst (237.3 μmol h⁻¹) and much higher than bare Zn_0.5Cd_0.5S (90.8 μmol h⁻¹). The active Cu⁺/Cu⁰ species generated during the photoreaction process is responsible for the prominent H₂-production activity of the heterojunction photocatalyst, which plays triple roles in enhancing the photoactivity of Zn_0.5Cd_0.5S via accelerating the charge separation, decreasing the overpotential of H₂-generation and improving the reduction ability of photoinduced electrons. Moreover, the formed Cu⁺/Cu⁰ species during photoreaction can be readily oxidized back to Cu₂(OH)₂CO₃ upon exposure to air, thus restores the photoactivity and therefore enables good reusability of the Cu₂(OH)₂CO₃/Zn_0.5Cd_0.5S heterojunction photocatalysts. This work provides a new insight into the fabrication of Cu₂(OH)₂CO₃-assisted heterojunction photocatalysts with the highly stable and efficient performances for solar-to-chemical energy conversion.