Seed-mediated growth of heterostructured Cu1.94S-MS (M=Zn, Cd, Mn) and alloyed CuNS2 (N=In, Ga) nanocrystals with structure- and composition-dependent photocatalytic hydrogen evolution
Multinary copper-based chalcogenides nanocrystals (NCs) as light-driven photocatalysts have attracted extensive research interests due to their great potential for sustainable energy without environmental concerns. Nevertheless, systematic studies on the growth mechanism and related photocatalytic activities involving different valent metal ions (either M2+ or N3+) as foreign cations and monoclinic Cu1.94S NCs as the ‘parent lattice’ have been rarely carried out. In this work, we report an effective seed-mediated method for the synthesis of heterostructured Cu1.94S-MS NCs (M= Zn, Cd and Mn) and alloyed CuNS2 NCs (N=In and Ga). A typical cation exchange process was taken place prior to the growth of heterostructured NCs, while further inter-cation diffusion was occurred only for the alloyed NCs. By benchmarking to the Cu1.94S NCs, all the heterostructured Cu1.94S-MS NCs and CuGaS2 NCs showed enhanced photocatalytic activities toward the water-splitting hydrogen production, owing to their tailored optical band gaps and energy level alignments. Though optically favored, CuInS2 NCs were not comparable to others due to their low conduction band minimum for reduction of H2O to H2.