Adapting Early Transition Metal and Nonmetallic Dopants on CoFe Oxyhydroxides for Enhanced Alkaline and Neutral pH Saline Water Oxidation

The development of earth-abundant electrocatalysts that are highly active and stable in saline electrolytes is a prerequisite toward the commercial realization of seawater electrolysis. In this work, we synthesized S,B-(CoFeCr) and S,B-(CoFeV) oxyhydroxides using a facile solution combustion synthesis (SCS) method for Co3O4 production followed by a simple wet chemistry doping strategy in an alkaline environment. Dopants of early transition metals (i.e., Cr and V) and nonmetals (i.e., S and B) were employed to synergistically enhance activity through surface modulation and to improve hydrophilicity toward water oxidation in neutral and near-neutral pH saline electrolyte. We performed an array of characterization techniques including high-resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) (pre- and post-OER) to characterize intrinsic properties of the developed catalysts. The as-prepared S,B-(CoFeCr)OOH and S,B-(CoFeV)OOH electrocatalysts required low oxygen evolution reaction (OER) overpotentials of 174 and 242 mV to achieve a current density of 10 mA cm–2 with low Tafel slopes of 45.8 and 52.3 mV dec–1, respectively, in an alkaline saline (1 M KOH + 0.5 M NaCl) electrolyte. Chronopotentiometric stability tests indicated a stable performance in a neutral pH saline environment for prolonged times with a curbed chlorine evolution reaction.