(560cg) The Role of Sulfur in CoSe(1-x)Sx for Enhanced Oxygen Electrocatalysis

Advanced electrochemical energy systems like metal air batteries, metal ion batteries, PEM fuel cells, and water electrolyzers have garnered a lot of interest. Limitation in efficiency and cost has been the critical barrier for any commercialization of these systems. Primary reactions occurring in a fuel cell or a battery consists of oxygen electrocatalysis i.e. oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Tremendous efforts have been made to study different aspects of Transition Metal Chalcogenides (TMDs) like its ORR/OER kinetics, facet interactions with O_ads and metal vacancy effects. Employing solvothermal techniques, we synthesized a series of CoSe_(1-x)S_x. With increasing sulfur incorporation, a phase transformation from hexagonal to cubic crystal structure. The formation and stability of Co₉S₈ comes from the octahedral Co atom linking at the center of the structure as opposed to CoS. Pure sulfide or selenide exhibited excellent current density with a low overpotential (0.767 V). The catalyst also exhibits low tafel slope of 57 and 44 mV/dec respectively. Pure CoSe showed stability upto 2000 cycles of CV. For exploring the fundamental aspects in detail, temperature programmed reduction studies to generate S vacancies leading to altered electron cloud densities at the active sites are in progress. Introduction of S_vac can also enhance charge transfer properties in the bulk.