Ir-free polymetal oxide electrode for efficient chlorine evolution reaction in acidic media

The chlorine evolution reaction is an anodic reaction in the chlor-alkali process, which utilizes dimensionally stable anodes (DSA) with large amounts of noble metals like iridium. Cheaper chlorine evolution anodes with high selectivity and stability are highly appealing but challenging. Here, a polymetallic oxide consisting of Sn, Ru, Nb, and Ti elements is synthesized on Ti felt for catalyzing chlorine evolution reaction. In particular, the Ru 0.3 Sn 0.6 Nb 0.1 O 2 film on Ti felt (i.e., Ru 0.3 Sn 0.6 Nb 0.1 O 2 /Ti) demonstrates a low overpotential of 42 mV at 10 mA cm −2 in 5 M NaCl (pH= 2) along with high Cl 2 selectivity (96.0 %) and mass activity (54.2 A g Ru −1 ) at 1.41 V versus reversible hydrogen electrode, which is 16 times higher than that of DSA electrode (3.2 A g Ru+Ir −1 ). Significantly, this anode can stably work for > 500 h at a current density of 100 mA cm −2 without attenuation. The flow cell fabricated with the Ru 0.3 Sn 0.6 Nb 0.1 O 2 /Ti anode and Pt/C cathode possesses excellent stability with a Cl 2 selectivity of 93 %, surpassing the flow cell fabricated with the DSA anode (81 %). The Ru 0.3 Sn 0.6 Nb 0.1 O 2 /Ti electrode exhibits low noble metal costs (7 % of DSA), and lower energy cost (82.5 % of DSA), but similar durability, showing great potential for industrial application.