A push-pull organic dye and a cobaloxime catalyst were successfully co-grafted on NiO and CuGaO 2 to form efficient molecular photocathodes for H 2 production with >80% Faradaic efficiency. CuGaO 2 is emerging as a more effective p-type semiconductor in photoelectrochemical cells and yields a photocathode with four-fold higher photocurrent densities and 400 mV more positive onset photocurrent potential compared to the one based on NiO. Such an optimized CuGaO 2 photocathode was combined with a TaON|CoO x photoanode in a photoelectrochemical cell. Operated in this Z-scheme configuration, the two photoelectrodes produced H 2 and O 2 from 2 water with 87% and 88% Faradaic efficiency, respectively, at pH 7 under visible light and in the absence of an applied bias, equating to a solar to hydrogen conversion efficiency of 5.4×10 −3 %. This is, to the best of our knowledge, the highest efficiency reported so far for a molecular-based noble metal-free water splitting Z-scheme.