Ru-optimized geometric sites of cations in CoFe/CoFe2O4 electrocatalysts with graphitic carbon shells for boosting water oxidation

Rational fabrication of an electrocatalyst with excellent stability, conductivity, and activity is urgently demanded for oxygen evolution reaction (OER). In this work, Ru-regulated hierarchical CoFe/CoFe 2 O 4 nanoparticles with graphitic carbon shells were successfully fabricated via self-assembling and vapor reduction strategies. Our investigation uncovers high concentrations of octahedral Co 3+ sites in electrocatalysts can be triumphantly acquired via moderate Ru doping, which could give rise to excellent electrocatalytic activities during OER. In addition, the design of CoFe alloys and graphitic carbon shells can compensate for the weak conductivity of cobalt ferrites. Based on the intrinsic stability, improved conductivity and activity, the as-prepared electrocatalyst yields a low overpotential of 237 mV at 10 mA cm −2 and a small Tafel slope of 47 mV dec −1 in 1.0 M KOH electrolyte, exhibiting outstanding electrocatalytic activities for OER.