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This work reports a simple chemical route to synthesize high surface area ceria (CeO2) nanoparticles which exhibit remarkable radical scavenging activity. Synthesized CeO2 nanoparticles are characterized by thermogravimetric analysis (TGA), X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR) and Raman spectroscopy, scanning electron microscopy (SEM), energy‐dispersive X‐ray analysis (EDX), transmission electron microscopy (TEM), and Brunauer‐Emmett‐Teller surface area (BET surface area) analyses. The characterization results reveal the formation of cubic phase of CeO2 with particles sizes of 10 nm and a remarkably high specific surface area of 236.8 m2/g. The nanoparticles are explored for 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) and hydroxyl radical scavenging activity that is to assess the antioxidant property of nanoceria by in‐vitro spectrophotometric approach.

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are considered as the core reactions in several alternative energy devices. Engineering the electronic structure of low-cost transition metal oxides (MOs) for the ORR and OER is highly demanding for such devices. Herein, a nonprecious mixed MO hybrid is reported that comprised of nanostructured Co 3 O 4 and CeO 2 supported on carbon (Co 3 O 4 −CeO 2 /C) with adequate oxygen vacancies and strong oxide/oxide and oxide/carbon heterointerfaces. The Co 3 O 4 −CeO 2 /C hybrid is highly active toward the ORR with values of the onset potential (−0.12 V) and Tafel slope (69 mV decade −1 ) comparable to that of benchmark Pt/C with a high limiting current density in alkaline medium. It can catalyze the OER efficiently at a less positive onset potential (0.23 V) and low Tafel slope (176 mV decade −1 ), in contrast with the standard RuO 2 catalyst (0.45 V and 179 mV decade −1 ). The remarkable activity of the Co 3 O 4 − CeO 2 /C hybrid represents a promising route to replace noble metals and to develop low-cost bifunctional electrodes for energy devices.