In this work we highlight a peculiar synthesis protocol for the p-type ternary metal oxide system of copper bismuth oxide (CuBi₂O₄), which yields a highly crystalline spherulitic morphology at a low temperature of 78 °C. We associate this growth with the hydrogen bonding effects imparted by the ethanol–water co-solvent system used for the synthesis. We present a detailed growth mechanism by evaluating different synthesis conditions systematically. Furthermore we show that upon the use of the non-stoichiometric (excess copper) precursor mixture under the same experimental conditions the growth of spherulitic CuBi₂O₄ changes the size and type of the spherulites. Interestingly, careful optimization of the non-stoichiometric synthesis presents a complete impediment to the spherulitic growth and produces a composite of nanorods of CuBi₂O₄ and nanosheets of CuO. This anisotropic nanocomposite shows an order of magnitude higher surface area as compared to spherulitic CuBi₂O₄. Since both CuBi₂O₄ and CuO are visible light absorbing p-type semiconductors, when the synthesized nanocomposite materials are examined as photoelectrochemical (PEC) photocathodes for water splitting, they show a remarkable dependence on the morphology and phase constitution. Almost 13-fold stronger PEC response is observed as the morphology changes from spherulites to nanorods.