  Kusachiite (copper bismuth oxide) is one of the most promising photocathode
materials for high solar-to-hydrogen production efficiency. Here we attempt to
synthesize phase pure copper bismuth oxide (CuBi2O4) nanopowders using a facile
solid-state reaction technique, subsequently sintered at 750 0C for 4 h in air.
These CuBi2O4 (CBO) powders have been further sequentially ball-milled (SBM) up
to 25 h to elucidate the milling duration effect on the optical bandgap of the
ball-milled CuBi2O4 (SBM-CBO). The X-ray diffractometry (XRD), Raman, X-ray
Photoelectron spectroscopy (XPS), and UV-VIS-NIR Diffuse reflection studies
suggest that phase pure tetragonal CBO could be grown from raw CuO and Bi2O3
powders. The variations in morphology and chemical composition of CBO with
increasing milling hours were examined using field emission scanning electron
microscopy (FE-SEM) and Energy Dispersive X-ray (EDX) microanalysis,
respectively. The optical bandgap of SBM-CBO powders was measured in the range
of approx. 1.70 - 1.85 eV. Photoelectrochemical studies of SBM-CBO slurry atop
the screen-printed electrode with aqueous Na2SO4 electrolyte suggest its
suitability as photocathode materials for sunlight-driven hydrogen production.
