Au/TiO2 thin film with ultra-low content of gold: An efficient self-supported bifunctional electrocatalyst for oxygen and hydrogen evolution reaction

Electrochemical water splitting has triggered much attention for the cost-effective production of hydrogen (H2) to alleviate the energy crises around the globe. Searching for efficient and scale able electrode materials to efficiently catalyze both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) at low overpotential is direly needed. Herein we report a scalable method to develop a thin film of Au@TiO2 on fluorinated tin oxide (FTO) with ultra-low content of Au (0.573 µg/cm2), which can dramatically sensitize the mesoporous TiO2 for OER and HER in alkaline medium (1 M KOH). The thin film was developed via spin coating with layer-by-layer deposition of TiO2 and Au at optimum concentration and temperature. The catalyst needed a small overpotential of 200 and 240 mV for the HER and OER, revealing a sustainable behavior for more than 60 h, mainly depending on the nature of the thin film, uniformly distributed small particles of Au, and their oxidation states/orbital occupancy. It is anticipated that sensitization of thin film of mesoporous TiO2 with an ultrasmall amount of Au could simultaneously realize the role of synergistic interaction of Au and TiO2, the oxidation state of Au0/1+ and self-supported/free standing nature of electrodes which are indeed very appealing to facilitate the mass and charge transport during energy intense water splitting process. We believe that such a facile and scalable pathway could provide a guiding principle to rationally design more efficient electrode material with minimum use of precious metals for the viable electrochemical water splitting processes.