Increasing Chlorine Selectivity through Weakening of Oxygen Adsorbates at Surface in Cu Doped RuO2 during Seawater Electrolysis

Abstract

During seawater electrolysis, both oxygen and chlorine evolve at anode and their selectivity can be modulated through variation of surface and electronic structure of the electrocatalyst. In this context, the selectivity toward chlorine evolution reaction (CER) during seawater electrolysis using electrodeposited Cu-doped RuO2 with lower doping concentration (2%) has been found to better than RuO2. Though Cu does not behave as an active site it reduces the binding energy of oxygen evolution reaction (OER) related intermediates (e.g. HO-, O-, HOO-) in neighboring Ru active sites and promotes both specific activity and selectivity of CER as suggested by both experimental and Density Functional Theory studies. However, due to aliovalent nature of Cu-dopant in RuO2 host, phase segregation and surface enrichment of dopants occur with increase in dopant concentration which reduces the overall activity and selectivity toward CER. Furthermore, increase in Cu-dopant would lower surface oxygen vacancy formation energy and promotes additional lattice-oxygen-vacancy aided water dissociation pathway resulting in enhancement of selectivity of OER. The present work offers insight on catalyst design taking account of selectivity of chlorine and oxygen evolution during seawater electrolysis.