IrO2-Modified RuO2 Nanowires/Nitrogen-Doped Carbon Composite for Effective Overall Water Splitting in All pH

Development of active catalysts for the electrochemical hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are of prime importance for the commercialization of the proton-exchange membrane (PEM)/anion-exchange membrane (AEM) water electrolyzer. Here, we report synthesis of an IrO2-modified RuO2 nanowires/nitrogen-doped carbon composite for overall water splitting at all pH. This catalyst exhibits excellent OER activity in 0.5 M H2SO4 solution with a low overpotential of 188 mV at 10 mA/cm2 current density, a low Tafel slope value of 42 mV/dec, and ∼96% faradic efficiency. The OER of this catalyst in neutral and base media is also higher than that of commercial RuO2 and IrO2. IrO2–RuO2/C also showed very good HER activity with 10 mA/cm2 current density at 82 and 75 mV overpotential in acid and base, respectively. The HER performance of this catalyst is better than that of commercial Pt/C in base and slightly lower in neutral and acid. The catalyst shows excellent OER and HER stability compared to the state-of-art catalysts. In addition, the overall water-splitting performance of IrO2–RuO2/C was also studied, which shows 10 mA/cm2 current density at 1.52 and 1.51 V cell voltage in 1.0 M KOH and 0.5 M H2SO4, respectively. The outstanding activity of the IrO2–RuO2/C catalyst can be attributed to a unique one-dimensional nanowire structure, synergistic interaction, high surface area, high oxophilicity, and high mass and electron transportation between IrO2, RuO2, and the carbon support. This work may provide an opportunity to design and synthesize a highly durable and efficient electrocatalyst for renewable energy conversion.