Crystalline nickel, cobalt, and manganese antimonates as electrocatalysts for the chlorine evolution reaction

The chlorine-evolution reaction (CER) is a common, commercially valuable electrochemical reaction, and is practiced at industrial scale globally. A precious metal solid solution of RuO₂ or IrO₂ with TiO₂ is the predominant electrocatalyst for the CER. Herein we report that materials comprised only of non-precious metal elements, specifically crystalline transition-metal antimonates (TMAs) such as NiSb₂O_x, CoSb₂O_x, and MnSb₂O_x, are moderately active, stable catalysts for the electrochemical oxidation of chloride to chlorine under conditions relevant to the commercial chlor-alkali process. Specifically, CoSb₂O_x exhibited a galvanostatic potential of 1.804 V vs. NHE at 100 mA cm^-2 of Cl₂(g) production from aqueous pH = 2.0, 4.0 M NaCl after 250 h of operation. Studies of the bulk and surface of the electrocatalyst and the composition of the electrolyte before and after electrolysis indicated minimal changes in the surface structure and intrinsic activity of CoSb₂O_x as a result of Cl₂(g) evolution under these conditions.