Accelerating oxygen evolution reaction via sodium extraction of Na0.71CoO2

Abstract Developing efficient and cost-effective electroctalysts to accelerate the sluggish kinetics of the oxygen evolution reaction (OER) is of great importance to emerging renewable energy technologies. In this work, a chemical sodium extraction of Na from low-cost Na 0.71 CoO 2 electrocatalyst was demonstrated as an effective way to enhance its catalytic activity and durability toward enhancing OER. By continuously extracting sodium ions out of Na 0.71 CoO 2 for 2 days, a low overpotential η (0.44 V) at 10 mA cm −2 , a good mass activity (65.93 mA mg −1 ) and a small Tafel slope (55 mV dec −1 ) were achieved, which are superior to those of using precious metal oxide IrO 2 . XPS measurements and BET surface areas investigations suggest that the dramatic improved OER performance should be ascribed to several major factors, including formed Co 4+ ions oxidized from Co 3+ , increased surface oxygen vacancies and enlarged specific surface areas occurred during the Na extraction process. The research here highlights the importance of tuning cation deficiency in Na-based oxides for further designing advanced OER electrocatalysts.