Boosting selective chlorine evolution reaction: Impact of Ag doping in RuO electrocatalysts.

The chlor-alkali process is critical to the modern chemical industry because of the wide utilization of chlorine gas (Cl). More than 95 % of global Cl production relies on electrocatalytic chlorine evolution reaction (CER) through chlor-alkali electrolysis. The RuO electrocatalyst serves as the main active component widely used in commercial applications. However, oxygen evolution reaction (OER) generally competes with CER electrocatalysts at RuO electrocatalyst owing to the intrinsically scaling reaction energy barrier of *OCl and *OOH intermediates, leading to decreased CER selectivity, high energy consumption, and increased cost. Here, the effect of Ag doping on selective CER over RuO electrocatalysts prepared by a sol-gel method has been systematically studied. We found that Ag-doping can effectively improve the Faradaic efficiency of RuO electrocatalyst for CER. Furthermore, the improved CER selectivity of Ag-doped RuO electrocatalysts is highly dependent on the Ag-doping concentration. The optimized AgRuO electrocatalyst displays an overpotential of 105 mV along with a selectivity of 84.64 ± 1.84 % in 5.0 M NaCl electrolyte (pH = 2.0 ± 0.05), significantly outperforming undoped one (142 mV, 72.75 ± 1.52 %). Our experiments and density functional theory (DFT) calculations show electron transfer from Ag to Ru suppresses *OOH intermediates desorption on Ag-doped RuO, enabling improved CER selectivity. Such designs of Ag-doped RuO electrocatalysts are expected to be favorable for practical chlor-alkali applications.