Noble metals doped tin dioxide for sodium hypochlorite synthesis from low concentrated NaCl solutions

Abstract BACKGROUND Creation of anode materials with high selectivity to the target process is the main problem in low concentration sodium chloride (NaCl) solutions. A specificity of such solutions is the achievement of high potentials at which the anodes traditionally used for the synthesis of chlorine [rutile oxide/titania (RuO 2 ‐TiO 2 )] are destroyed. The main aim of the work concerns the eveluation of the effect of platinum (Pt) group metals in a tin oxide (SnO 2 ) matrix on the electrocatalytic activity and selectivity in reactions of the synthesis of sodium hypochlorite and chlorate (NaClO and NaClO 3 ) and oxygen (O 2 ) evolution. RESULTS It was revealed that palladium (Pd) in oxide Ti/SnO 2 ‐Pd and Ti/SnO 2 ‐Pt‐Pd coatings existed in the PdO form, which has a high affinity for hydroxylation. Electrocatalytic activity of coatings in anode processes in low concentrated chloride‐containing solutions would be determined by the bond strength of chemisorbed with the surface O‐containing particles. Participation in the process of Cl ‐ oxidation of labile O‐containing particles increased the rate of formation of NaClO and led to inhibition of adverse reactions of O 2 evolution and synthesis of chlorates and chlorites. CONCLUSION A correlation between the selectivity of formation of NaClO and NaClO 3 , and the activity of the catalyst in the O 2 evolution reaction is proposed. Significant formation of chlorates occurred only at the anodes, where in 1 mol L –1 HClO 4 the O 2 evolution potential was >1.58 V. Parameters influencing the electrocatalytic activity and selectivity of electrode materials in the target process were proposed based on this dependence. © 2021 Society of Chemical Industry (SCI).