Single-step solution plasma synthesis of bifunctional CoSn(OH)6–carbon composite electrocatalysts for oxygen evolution and oxygen reduction reactions†

Abstract

Development of efficient bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is highly required for the application in rechargeable metal–air batteries. Many research groups continue to develop active materials that enhance ORR and/or OER, aiming to improve the electrocatalytic properties and durability of electrodes in metal–air batteries. Currently, the most commonly used materials for ORR/OER catalysts are precious metals, that need to be replaced by low-cost catalysts with comparable performance. We have successfully synthesized non-precious metal-based catalytic composite materials composed of perovskite hydroxide, CoSn(OH)₆ (CSO), and carbon materials via the solution plasma process (SPP). SPP realized the single step synthesis of carbon composite materials with the formation of CSO nanoparticles and provides excellent control over the nanostructure of the catalysts. The process can induce unique surface properties due to the plasma environment, potentially enhancing catalytic activity. The synthesized CSO and carbon composite catalysts exhibited promising catalytic properties for both ORR and OER. For ORR, the CSO and Ketjen Black (KB) composites, synthesized at pH 12, achieved the highest potential value at a current density of −3 mA cm⁻². In OER, the same CSO and KB composite material synthesized at pH 12 reached the lowest potential value at a current density of 10 mA cm⁻², surpassing the performance of RuO₂. This study demonstrated the potential to customize and manufacture high-performance and low-cost bifunctional electrocatalysts for energy conversion systems by single-step synthesis, offering a sustainable materials alternative to commercialized precious metal-based electrocatalysts.