Engineering [Fe(CN)6]3− vacancy via free-chelating agents in Prussian blue analogues on reduced graphene oxide for efficient oxygen evolution reaction

Development of efficient and durable electrocatalysts for the oxygen evolution reaction (OER) is essential for sustainable hydrogen production by water splitting. The physicochemical properties of the electrocatalyst can be tailored by defect engineering. Herein, we report the fabrication of [Fe(CN)6]3− coordination sphere vacancies via the rapid coprecipitation in Ni3Ⅱ[FeIII (CN)6]2-x (x ≤ 0.12) electrocatalyst anchored on reduced graphene oxide (v-NiFe [email protected]) for OER. The formation of [Fe(CN)6]3− coordination sphere vacancies (VFeCN) via the rapid coprecipitation during the synthesis under the absence of chelating agents enables the regulation of electronic states of Ni active site, leading to the improvement in OER. Reduced graphene oxide (rGO) is employed as a substrate to maximize the concentration of VFeCN and exposed active sites by the uniform formation of nano-sized Ni3Ⅱ[FeIII (CN)6]2-x. The presence of VFeCN and hybridization with rGO effectively suppress Fe leaching behavior. The v-NiFe [email protected] shows a low overpotential of 251 mV at 10 mA cm−2 in alkaline condition and the long-term stability for 200 h.