Boosting selective chlorine evolution reaction: Impact of Ag doping in RuO2 electrocatalysts

The chlor-alkali process is critical to the modern chemical industry because of the wide utilization of chlorine gas (Cl 2 ). More than 95 % of global Cl 2 production relies on electrocatalytic chlorine evolution reaction (CER) through chlor-alkali electrolysis. The RuO 2 electrocatalyst serves as the main active component widely used in commercial applications. However, oxygen evolution reaction (OER) generally competes with CER electrocatalysts at RuO 2 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 2 electrocatalysts prepared by a sol–gel method has been systematically studied. We found that Ag-doping can effectively improve the Faradaic efficiency of RuO 2 electrocatalyst for CER. Furthermore, the improved CER selectivity of Ag-doped RuO 2 electrocatalysts is highly dependent on the Ag-doping concentration. The optimized Ag 0.15 Ru 0.85 O 2 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 4+ suppresses *OOH intermediates desorption on Ag-doped RuO 2 , enabling improved CER selectivity. Such designs of Ag-doped RuO 2 electrocatalysts are expected to be favorable for practical chlor-alkali applications.