Brand new 1D branched CuO nanowire arrays for efficient photoelectrochemical water reduction

Developing high surface area nanostructured electrodes with fast charge separation is one of the main challenges for exploring cupric oxide (CuO)-based photocathodes in solar-driven hydrogen production applications. Herein, brand new 1D branched CuO nanowire arrays have been achieved on fluorine-doped tin oxide-coated glass (FTO) through a two-step wet chemical redox reaction. X-ray diffraction patterns, Raman spectra and X-ray photoelectron spectroscopy confirm the pure phase characteristic of the resulting branched CuO. In addition to the enlarged surface area of this advanced functional structure as compared with that of the 1D wire trunk, the charge injection and separation have been improved by rationally controlling the density of defects and size of branches. As a result, the optimized branched CuO exhibits photocurrent as high as 3.6 mA·cm-2 under AM 1.5G (100 mW·cm-2) illumination and 3.0 mA·cm-2 under visible light (λ > 420 nm) at 0.2 V vs. RHE in 0.5 M Na2SO4, which are 2.8- and 3.0-fold greater than those of 1D wire samples, respectively. In addition, the solution-processed approach established herein seems quite favourable for large-scale and low-cost manufacturing.