Seed-mediated growth of heterostructured Cu_1.94S–MS (M = Zn, Cd, Mn) and alloyed CuNS₂(N = In, Ga) nanocrystals for use in structure- and composition-dependent photocatalytic hydrogen evolution

Abstract

Multinary copper-based chalcogenide nanocrystals (NCs) as light-driven photocatalysts have attracted extensive research interest due to their great potential for generating sustainable energy without causing environmental concerns. However, systematic studies on the growth mechanism and related photocatalytic activities involving different valent metal ions (either M²⁺ or N³⁺) as foreign cations and monoclinic Cu_1.94S NCs as the 'parent lattice' have rarely been carried out. In this work, we report an effective seed-mediated method for the synthesis of heterostructured Cu_1.94S-MS NCs (M = Zn, Cd and Mn) and alloyed CuNS₂ NCs (N = In and Ga). A typical cation exchange process took place prior to the growth of heterostructured NCs, while further inter-cation diffusion occurred only for the alloyed NCs. When compared with Cu_1.94S NCs, all the heterostructured Cu_1.94S-MS NCs and CuGaS₂ NCs showed enhanced photocatalytic activities toward hydrogen production by water splitting, owing to their tailored optical band gaps and energy level alignments. Although optically favored, CuInS₂ ANCs were not comparable to others due to their low conduction band minimum for the reduction of H₂O to H₂.