Inside-Out: The Role of Buried Interfaces in Hybrid Cu₂ZnSnS₄-Noble Metal Photocatalysts

Metal-semiconductor hybrids are a promising architecture for functional nanostructures because they efficiently promote charge separation. The morphology of the hybrid supports two mechanisms of charge generation and transfer, namely, the excitation of electrons to the conduction band of the semiconductor or the induction of surface plasmon resonance on the metal. Here, we compared the photocatalytic activity of nanoparticles with a core-shell or dimer morphology, using Pt, Pd, or Au as the metal and Cu₂ZnSnS₄ (CZTS), which comprises abundant and environmentally friendly elements, as the semiconductor. Their performance as photocatalysts was evaluated by using Methylene Blue (MB) degradation under light irradiation. We found that although large Au cores improved the photocatalytic activity of the CZTS nanoparticles, the highest catalytic activity was that of Pt-CZTS and Pd-CZTS dimers. Conversely, using small metal particles as cores degraded the activity of the CZTS due to the formation of an internal boundary and the occupation of potentially optically active volume. In addition, the results point out that depositing multiple metal particles is not beneficial for photocatalysis.