Oxygen vacancies engineering by coordinating oxygen-buffering CeO₂ with CoO_x nanorods as efficient bifunctional oxygen electrode electrocatalyst

CeO₂ decorated CoO_x rod-like hybrid, supported onto holey reduced graphene (CoO_x/CeO₂/RGO) composite, was fabricated via a surfactant-assisted route. Its corresponding electrocatalytic performance towards oxygen reduction/evolution reactions (ORR and OER) was systematically investigated in alkaline electrolyte. Structural, morphological and compositional studies revealed changes in electronic and surface properties when CeO₂ was introduced as an oxygen buffer material. The oxygen vacancies effectively enhanced the electrocatalytic activity, while the synergistic effect of co-catalyst CeO₂, CoO_x active-centers, and defective graphene with many voids facilitate the charge/mass transfer, making CoO_x/CeO₂/RGO an efficient and stable bifunctional electrocatalyst for OER/ORR with ΔE = 0.76 V (ΔE = E_{10 mA cm}^-2,_OER – E_{1/2, ORR}). This parameter is 70 mV and 270 mV lower than CoO_x/RGO and the benchmark Pt/C, respectively. In addition, the OER/ORR bifunctionality of CoO_x/CeO₂/RGO composite outperforms that of Pt/C catalyst in a H₂-O₂ micro fuel cell platform.