On the Synergism between Cu and Ni for Photocatalytic Hydrogen Production and their Potential as Substitutes of Noble Metals

A series of Cu(OH) 2 –Ni(OH) 2 /P25 photocatalysts was prepared by co‐deposition–precipitation (total metal loading ≈1 wt %) and their performance was evaluated for H 2 production. Among this series, the 0.8 Cu(OH) 2 –0.2 Ni(OH) 2 /P25 photocatalyst demonstrated very high H 2 production rates in 20 vol % ethanol/water and 5 vol % glycerol/water mixtures (10 and 22 mmol h −1 g −1 , respectively). Detailed analyses based on reaction kinetics, photoluminescence, X‐ray photoelectron spectroscopy (XPS), and charge carrier scavenging suggest that both working catalysts are composed of Cu and Ni metals in their active phases. Cu 0 is produced directly by the transfer of electrons from the conduction band of TiO 2 to surface Cu(OH) 2 nanoclusters, whereas Ni 0 is formed indirectly through a process of gradual dissolution of Ni(OH) 2 to yield aqueous Ni 2+ owing to the acidic environment of the medium, followed by Ni 2+ reduction by electrons from the TiO 2 conduction band. The high rates of H 2 production that match those obtained with noble metals can be explained owing to a considerably less negative Δ G o of Cu oxide formation when compared with that of Ni oxide formation and higher work function of Ni than that of Cu.