Solution plasma synthesis of perovskite hydroxide CoSn(OH)6 nanocube electrocatalysts toward the oxygen evolution reaction

Abstract

To realize high-performance lithium–air batteries, it is necessary to develop a catalyst material that promotes the redox reaction of oxygen. Perovskite-type oxides and hydroxides are known as catalyst materials for accelerating the oxygen evolution reaction (OER). CoSn(OH)₆ (CSO) is a perovskite-type hydroxide that is a promising catalyst for the OER. In this study, the synthesis and characterization of CSO using a solution plasma process were reported. By using this process, CSO could be synthesized in 20 min. X-ray diffractometry (XRD) results revealed that highly crystalline CSO can be synthesized by adjusting the pH of the precursor solution to more than 10 to 12. The synthesized CSO had a cubic shape and its size was approximately 100 to 300 nm. X-ray photoelectron spectroscopy (XPS) results showed that the valences of Co and Sn in CSO were divalent and tetravalent, respectively. The catalytic properties of the synthesized CSO for the OER were evaluated using an electrochemical method. The overpotential at 10 mA cm⁻² and Tafel gradient of the synthesized samples at pH12 (CSO_pH12sp) were estimated to be 350 mV and 69.58 mV per decade, respectively. The CSO_pH12sp sample showed the most superior catalytic properties among all samples synthesized and the catalytic properties were slightly superior to those of commercial RuO₂. When the current density reached 10 mA cm⁻², the potential of CSO_pH12sp was the lowest, which was 104 mV lower than that of commercially available RuO₂vs. RHE. From the results of optical emission spectroscopy, the active species formed in the plasma were clarified and the mechanism of CSO synthesis was discussed based on the active species.