Carbon quantum dots decorated Cu2S nanowire arrays for enhanced photoelectrochemical performance

Abstract

The photoelectrochemical (PEC) performance of Cu₂S nanowire arrays (NWAs) has been demonstrated to be greatly enhanced by dipping-assembly of carbon quantum dots (CQDs) on the surfaces of Cu₂S NWAs. Experimental results show that the pristine Cu₂S NWAs with higher aspect ratios exhibit better PEC performance due to the longer length scale for light absorption and the shorter length scale for minority carrier diffusion. Importantly, the CQDs decorated Cu₂S NWAs exhibit remarkably enhanced photocurrent density, giving a photocurrent density of 1.05 mA cm⁻² at 0 V vs. NHE and an optimal photocathode efficiency of 0.148% under illumination of AM 1.5G (100 mW cm⁻²), which is 4 times higher than that of the pristine Cu₂S NWAs. This can be attributed to the improved electron transfer and the energy-down-shift effect of CQDs. We believe that this inexpensive Cu₂S/CQD photocathode with increased photocurrent density opens up new opportunities in PEC water splitting.