Glycine-induced ultrahigh-surface-area IrO2@IrOx catalyst with balanced activity and stability for efficient water splitting.

Polymer electrolyte membrane water electrolysis (PEMWE) uses intermittent renewable energy and plays a key role in storing energy in the form of hydrogen. However, its widespread application is limited owing to issues associated with oxygen evolution reaction (OER) catalysts, including activity and stability. Thus, it is necessary to develop highly active and durable catalysts in this regard. Herein, an IrO x @IrO 2 catalyst with an ultrahigh surface area (G-450) was synthesized by a simple Adams fusion method and calcined at 450 °C with glycine as an additive. Owing to its micro/mesoporous structure, this catalyst exhibited an ultrahigh specific surface area (SSA) of 403 m2 g-1 and an amorphous structure with average oxidation states of Ir(IV). A trade-off between its OER activity and stability was achieved by controlling its SSA and Ir oxidation states via the optimization of the calcination temperature. Surface-rich Ir(III) species and high SSA enhanced the OER activity of G-450 (309 mV overpotential at 10 mA cm-2) compared with the IrO 2 catalyst prepared without glycine (A-450, 351 mV overpotential at 10 mA cm-2). Further, the G-450 exhibited an Ir dissolution rate that was 2.5-fold lower than that of the IrO 2 catalyst prepared at 350 °C (G-350) after 6 h chronopotentiometry at 10 mA cm-2, implying a higher stability owing to the presence of Ir(IV) species. Additionally, G-450 was introduced into the anode of the polymer electrolyte membrane (PEM) water electrolyzer single cell and demonstrated higher performance than A-450. The balanced activity and stability of IrO x @IrO 2 enhanced the PEM water electrolyzer performance. Moreover, this facile synthetic method is also applicable to the synthesis of binary oxide compounds and other transition metal oxides. [Display omitted] [ABSTRACT FROM AUTHOR]