Highly Efficient and Selective Metal Oxy-Boride Electrocatalysts for Oxygen Evolution from Alkali and Saline Solutions

With a motivation to discover efficient materials for direct electrolysis of seawater, bimetallic oxy-boride (Co–Fe–O–B) nanostructures were developed using a facile hydrothermal synthesis strategy, with varying content of Fe. The oxygen evolution performance of the optimized Co–Fe–O–B catalyst in alkali water (1 M KOH) showed higher reaction rates owing to a Co3O4–core–Co2B-shell structure, which assists in the formation of active CoOOH species at lower potentials and offers a smaller charge-transfer resistance. The best-performing catalyst in alkali water was found to be highly active (294 mV to achieve 10 mA/cm2) in saline water (1 M KOH + 0.5 M NaCl), with 100% O2 selectivity, establishing its potential for seawater electrolysis. The high activity and selectivity of the oxy-boride catalyst in alkaline saline electrolyte presents a fresh avenue for research in low-cost materials, especially boron-containing compounds, for selective seawater splitting.