Cu-deficient plasmonic Cu2-xS nanocrystals induced tunable photocatalytic activities
Copper sulfide (Cu2-xS) is a kind of cation deficient transition metal sulfides, which have attracted interests greatly due to their unique properties that arise from degenerate vacancy-doping, particularly their tunable localized surface plasmon resonances (LSPR) property. In this work, a range of vacancy-doped Cu2-xS nanocrystals (NCs) (Cu1.2S, Cu1.4S, Cu1.75S, and Cu1.94S NCs) with size around 10 nm were prepared with tunable LSPR through a hot injection method. The doping level was manipulated effectively by varying the injection volume of sulfur powder-oleic acid (S-OA) to finely tune the LSPR wavelength. Cu2-xS NCs with four different doping levels were investigated as photocatalysts for degradation of dyes. The Cu1.94S NCs with the highest LSPR energy exhibited the best photocatalytic activity due to the highest free carrier density, presumably influenced by Cu vacancies and volume of S-OA solution. The theoretical calculations of free carrier density of Cu2-xS NCs are consistent with the order of photocatalytic activity. The results demonstrate that the correlation of photocatalytic activity with corresponding concentration of free holes and LSPR wavelength is of interest, which will provide inspirations for the design of non-noble metal catalysts by regulating the free hole concentration in degenerate p-doped Cu2-xS caused by cation vacancies.