Highly Active Oxide Photocathode for Photoelectrochemical Water Reduction

A clean and efficient way to overcome the limited supply of fossil fuels and the greenhouse effect is the production of hydrogen fuel from sunlight and water through the semiconductor/water junction of a photoelectrochemical (PEC) cell, where energy collection and water electrolysis are combined into a single semiconductor electrode. We present a highly active photocathode for solar H₂ production, consisting of electrodeposited cuprous oxide, which was protected against photocathodic decomposition in water by nanolayers of Al-doped zinc oxide and titanium oxide deposited by atomic layer deposition (ALD) and activated for hydrogen evolution with electrodeposited Pt nanoparticles. The roles of the different surface protection components were investigated, and in the best case electrodes showed photocurrents up to –7.6 mA cm^–2 at a potential of 0 V vs. RHE  (Reversible Hydrogen Electrode) at mild pH. The electrodes remained active after 1h of testing, cuprous oxide was found to be stable during the water reduction reaction and the Faradaic efficiency was estimated to be close to 100%.