Sulfur‐Modified Oxygen Vacancies in Iron–Cobalt Oxide Nanosheets: Enabling Extremely High Activity of the Oxygen Evolution Reaction to Achieve the Industrial Water Splitting Benchmark

Abstract

Water electrolysis is a promising strategy for high‐purity hydrogen production but restrained by the high electricity cost. Developing an oxygen evolution reaction (OER) electrocatalyst with excellent activity and low price is indispensable for reducing water electrolysis cost. The modulation of electronic structure of catalysts can be an efficient strategy to boost their activities. Herein, the oxygen vacancies of defective iron‐cobalt oxide (FeCoO x ‐Vo) nanosheets are modified by the homogeneously distributed sulfur (S) atoms. S atoms can not only effectively stabilize oxygen vacancies (Vo), but also form the Co‐S coordination with Co active site in the Vo, which can modulate the electronic structure of the active site, enabling FeCoO x ‐Vo‐S to exhibit much superior OER activity. Remarkably, FeCoO x ‐Vo‐S exhibits a mass activity of 2440.0 A g ‐1 at the voltage of 1.5 V vs. RHE in 1.0 M KOH, which is 25.4 times higher than that of RuO 2 (96.0 A g ‐1 ). Meanwhile, its Tafel slope can as low as 21.0 mV dec ‐1 , indicative of its excellent charge transfer rate. When FeCoO x ‐Vo‐S (anode catalyst) is paired with the defective CoP 3 /Ni 2 P (cathode catalyst) for overall water splitting, the current densities can be achieved as high as 249.0 mA cm ‐2 and 406.0 mA cm ‐2 at the cell voltage of 2.0 V and 2.3 V, respectively, which meet well the requirement of industrial water splitting.