Electrochemical and photoelectrochemical oxygen evolution reactions by Group X hetero-metal oxides

Electrochemical and photoelectrochemical water splitting methods must be developed to establish a sustainable energy system. In this study, we prepared Group X hetero-metal oxides and studied their (photo)electrochemical properties. Their electrochemical oxygen evolution activities improved as follows: PtO ≪ Ni/NiO < PdO + Ni/NiO < PtO_x + Ni/NiO. During deposition of the nanoparticles on a nanorod-shaped TiO₂ surface, we observed interesting chemical and photoelectrochemical reactivities varied by the hetero-metal oxides nanoparticles. The Group X hetero-metal oxides on the TiO₂ photoanode systematically enhanced catalytic activities for the photoelectrochemical oxygen evolution reaction, while decreasing the surface charge recombination and modulating the TiO₂ band gap. The Pt/PtO_x + Ni/NiO hetero-metal oxides acted as the most efficient cocatalyst on the TiO₂ surface with a photocurrent of 2.62 mA/cm² at 1.23 V vs. RHE and 70% IPCE value, which is ~4 times higher than a pristine TiO₂.