Supporting IrO_x nanosheets on hollow TiO₂ for highly efficient acidic water splitting

The efficiency of proton exchange membrane water electrolysis (PEM-WE) for hydrogen production is heavily dependent on the noble metal iridium-based catalysts. However, the scarcity of iridium limits the large-scale application of PEM-WE. To address this issue, it is promising to select an appropriate support because it not only enhances the utilization efficiency of noble metals but also improves mass transport under high current. Herein, we supported amorphous IrO_x nanosheets onto the hollow TiO₂ sphere (denoted as IrO_x), which demonstrated excellent performance in acidic electrolytic water splitting. Specifically, the annealed IrO_x catalyst at 150 °C in air exhibited a mass activity of 1347.5 A·g_Ir⁻¹, which is much higher than that of commercial IrO₂ of 12.33 A·g_Ir⁻¹ at the overpotential of 300 mV for oxygen evolution reaction (OER). Meanwhile, the annealed IrO_x exhibited good stability for 600 h operating at 10 mA·cm⁻². Moreover, when using IrO_x and annealed IrO_x catalysts for water splitting, a cell voltage as low as 1.485 V can be achieved at 10 mA·cm⁻². The cell can continuously operate for 200 h with negligible degradation of performance.