Copper oxide photocathodes prepared by a solution based process

Solution based processes are well known by their low-cost trait to fabricate semiconductor devices. In this study, we devised an economical solution based route to photoelectrochemical (PEC) cells, taking copper nitrate as the copper ion source and adding an alkali hydroxide, here NaOH, to produce high aspect ratio (3.1–9.7) CuO nanoparticles. These CuO particles were used for splitting water and generation of hydrogen via a PEC cell. CuO nanoparticle morphology, i.e. rod-like, spindle-like, and needle-like, was dependent on the processing temperature. Sintering the spin coated CuO films, improved crystallinity. The bandgaps for these films were estimated to be 1.35 eV and 1.64 eV for sintering temperatures of 600 °C and 400 °C for 1 h, respectively. The porous structure of the nano-sized CuO films increased surface area and thus led to a high photocurrent, i.e. 1.20 mA/cm², for powder prepared at 60 °C and sintered at 600 °C for 1 h. These films demonstrated 0.91% solar conversion efficiency at an applied voltage of −0.55 V vs. Ag/AgCl in 1 M KOH electrolyte with 1 sun (AM1.5G) illumination. The charge carrier density was estimated to be 6.1 × 10²⁰ cm⁻³. This relatively high charge carrier density may be due to the high surface area and short transport distance to the electrode/electrolyte interface in the porous nanostructure.