S-modified oxygen vacancies in iron-cobalt oxide nanosheets: Enabling extremely high activity of oxygen evolution reaction for achieving industrial water splitting benchmark.

The oxygen vacancies of defective iron-cobalt oxide (FeCoOx-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 FeCoOx-Vo-S to exhibit much superior OER activity. FeCoOx-Vo-S exhibits a mass activity of 2440.0 A g(-1)at 1.5 V vs. RHE in 1.0 mKOH, 25.4 times higher than that of RuO2. The Tafel slope is as low as 21.0 mV dec(-1), indicative of its excellent charge transfer rate. When FeCoOx-Vo-S (anode catalyst) is paired with the defective CoP3/Ni2P (cathode catalyst) for overall water splitting, current densities of as high as 249.0 mA cm(-2)and 406.0 mA cm(-2)at a cell voltage of 2.0 V and 2.3 V, respectively, can be achieved.