Facile low temperature ammonolysis synthesis of CeO2-xNx for enhanced photoelectrochemical H2 generation

[Display omitted] •Low temperature synthesis of CeO2-xNx phases by ammonolysis of cerium nitrate.•Method of synthesis and photoelectrochemical HER efficiency correlated.•Tuning redox properties by substituting N and creating anionic vacancies.•Carbon-free oxynitride materials for overall water splitting. A facile solid–gas interface method for anionic substitution of nitrogen in CeO2 lattice is reported. In this study, a low temperature ammonolysis method is developed as an alternate to high temperature ammonolysis of CeO2. Cerium nitrate precursor is thermally treated directly by ammonia gas at 550 °C to prepare cerium-oxy-nitride samples which are tested for photoelectrochemical hydrogen evolution activity (HER). The CeO2-xNx material synthesized by low temperature ammonolysis of cerium nitrate shows lower onset potential ηlight = -1.04 V vs Ag/AgCl under light, large photocurrent density of 0.2 µA/cm2 at −0.4 V applied potential. The proposed method of ammonolysis of salt precursors is an excellent method for the synthesis of oxy-nitrides at low temperatures without residual carbon impurities for higher photocatalytic efficiencies.