The photocatalytic properties of different calcium tantalate nanocomposite photocatalysts with optimized phase composition were studied without the addition of any co-catalysts in the photoreforming of different alcohols including the biomass conversion by-product glycerol, as well as after modification with double-layered NiOx (Ni/NiO) co-catalyst in overall water splitting (OWS). Nanocomposite photocatalyst consisting of cubic α-CaTa2O6/orthorhombic β-CaTa2O6 coexisting phases always possesses the highest photocatalytic performance. For overall water splitting, a loading of 0.5 wt. % NiOx exhibits the best activities with stable stoichiometric H2 and O2 evolution rates.