Correlation between oxygen evolution overpotential and selectivity of platinum group metal anodes for hypochlorite formation in low‐concentration NaCl solutions

Abstract BACKGROUND Electrochemical synthesis of hypochlorous acid (HOCl) and sodium hypochlorite (NaOCl) from low‐concentration sodium chloride (NaCl) solutions is becoming increasingly demanded to produce preparations suitable for medical applications. Such processes are complicated by several competing reactions, including oxygen evolution (OER) and the formation of sodium chlorate (NaClO 3 ), the current efficiency (CE) of which is determined by the anode materials. The aim of this work is to establish a correlation between the nature of platinum group metals deposited on platinized titanium (Ti/Pt) anodes and the selectivity of such anodes toward the active chlorine synthesis. RESULTS On Ti/Pt anodes, rapid surface passivation and low (30%–44%) CE (NaOCl) were observed, with significant (16%–25%) chlorate formation. Surface modification with palladium (Pd) followed by heat treatment (HT) prevented passivation. On Ti/Pt‐Pd‐HT anodes, the CE(NaOCl) reached 94%–97%. A direct correlation was found between selectivity and OER overpotential in 1.0 M HClO 4 : maximum HOCl selectivity was achieved at OER potentials within 1.56–1.66 V. Moreover, palladium oxides promote surface hydroxylation, facilitating water adsorption and product desorption. CONCLUSION Ti/Pt anodes modified with Pd provide an optimal combination of characteristics in the active chlorine synthesis from dilute NaCl solutions. The established correlations demonstrate that catalytic activity in the OER can serve as a reliable criterion for screening anode materials. The obtained results offer a practical strategy for the development of highly selective systems to produce chlorine‐active compositions for biomedical applications. © 2026 Society of Chemical Industry (SCI).