Crystalline cobalt antimonate as a noble-metal-free electrocatalyst for chlorine evolution: Wastewater treatment application and active site identification

Abstract

Dimensionally stable anodes (DSAs), consisting of a Ti base and platinum group metal (PGM) oxide as the active coating layer, have been employed in chlor-alkali industry and electrochem. wastewater treatment. However, their larger-scale application has been limited by the extensive use of PGM oxides such as RuO₂ and IrO₂, which results in not only high cost, but also long-term instability due to the dissoln. of Ru and Ir. Cryst. cobalt antimonate (CoSb₂O₆) has been recently demonstrated as an acid-stable noble-metal-free electrocatalyst for chlorine evolution and oxygen evolution, which makes it an ideal alternative to RuO₂ and IrO₂ in wastewater electrolysis. However, so far, the development of CoSb₂O₆ has relied on quartz or fluorine-doped tin oxide (FTO) glass as the substrate, which hinders its real-world application. Furthermore, the active catalytic site has not been identified. Herein, Ti-based CoSb₂O₆ has been fabricated by electrodeposition. The electrocatalytic performance was studied using linear sweep voltammetry (LSV), with the c.d. normalized to electrochem. active surface area (ECSA). Under an applied potential of 1.5 V vs. SCE, the CoSb₂O₆ electrode had a c.d. of 1.36 mA cm⁻² in 5 M NaCl soln., approaching the performance of RuO₂ (1.68 mA cm⁻²). On the other hand, the CoSb₂O₆ electrode had a c.d. of 2.22 mA cm⁻² at 3 V in 100 mM NaClO₄ soln., substantially higher than that of RuO₂ (0.64 mA cm⁻²). The wastewater treatment performance of the CoSb₂O₆ electrode was assessed under const. current condition. Meanwhile, DFT calcn. was employed to unravel the catalytically active site.