Seed-mediated phase-selective growth of Cu2GeS3 hollow nanoparticles with huge cavities

Abstract

Although significant progress has been achieved in the synthesis of hollow nanoparticles (NPs), research on copper-based multinary chalcogenide (CMC) semiconductor NPs with hollow structures is still less developed. In this work, we demonstrate an effective method for the phase-selective synthesis of cubic Cu₂GeS₃ hollow NPs (HNPs) with huge cavities and thin shells. This method includes the nucleation of Cu_2−xS seeds, followed by unequal diffusion between Cu⁺ and Ge⁴⁺. A common rule for the phase-selective growth of CMC NPs has been revealed: the nucleation step is the crystal phase-determining step in the growth process of CMC NPs, and the sulfur sources govern the crystal phase of the nucleus. Because of their huge cavities, the as-prepared large Cu₂GeS₃ HNPs are proved to be macroporous materials with a specific surface area of 22.1 m² g⁻¹. Besides, cubic Cu₂GeS₃ HNPs with small cavities are also synthesized, following the same method with little modification. By integrating the advantages of the large Cu₂GeS₃ HNPs (high surface-to-volume area) and the small Cu₂GeS₃ HNPs (good dispersibility and monodispersity), a new kind of two-layer photoelectrode is prepared. Compared with the photoelectrodes prepared using pure large and small Cu₂GeS₃ HNPs, the two-layer photoelectrode exhibits superior performance for photoelectrochemistry due to the high interface area of the upper layer and the ideal compactness of the bottom layer.