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.
This paper reports a facile self‐templated method to prepare hierarchically CuInS2 nanosheet‐constructed nanowire arrays (NCNAs) using Cu2S nanowires arrays (NWAs) as the template. The as‐synthesized CuInS2 nanosheets show ultrathin thickness of ≈1.2 nm, corresponding to the thickness of 4 atomically thick CuInS2 slab along the [221] direction. The CuInS2 nanosheet‐constructed nanowires exhibit diameters of several hundred nanometers and lengths of several micrometers. The novel exchange‐peeling growth mechanism suggests that the In3+ insertion proceeds preferentially along the (−204) facets of pristine Cu2S nanowires, and the distortions and strains sourced from lattice mismatch cause the longitudinal expansion along the c‐axis and the splitting of S−S bond during the formation of 3D CuInS2 NCNAs. It is also found that relative higher In3+ concentration is beneficial to this process. Compared to 0.15 mA cm−2 of the pristine Cu2S NWAs, the CuInS2 photocathodes show an enhanced photocurrent of 0.49 mA cm−2 at −0.1 V versus the reversible hydrogen electrode, and the photocurrent can be further increased to 1.14 mA cm−2 via decoration with CdS quantum dots. The density functional theory calculation results confirm that the ultrathin CuInS2 nanosheets favor for higher carrier mobility, thus ensure promoted photoelectrochemical efficiency.
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