Intercalated iridium diselenide electrocatalysts for efficient pH-universal water splitting

Developing bifunctional catalysts for both hydrogen and oxygen evolution reactions is a promising approach to the practical implementation of electrocatalytic water splitting. However, most of the reported bifunctional catalysts are only applicable to alkaline electrolyzer, although a few are effective in acidic or neutral media that appeals more to industrial applications. Here, a lithium-intercalated iridium diselenide (Li-IrSe${}_2$) is developed that outperformed other reported catalysts toward overall water splitting in both acidic and neutral environments. Li intercalation activated the inert pristine IrSe${}_2$ via bringing high porosities and abundant Se vacancies for efficient hydrogen and oxygen evolution reactions. When Li-IrSe${}_2$ was assembled into two-electrode electrolyzers for overall water splitting, the cell voltages at 10 mA cm${}^{-2}$ were 1.44 and 1.50 V under pH 0 and 7, respectively, being record-low values in both conditions. (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)