Metal–OrganicFramework-Derived Amorphous Cobalt–VanadiumOxide on MWCNT: A Superior Bifunctional Catalyst for Oxygen Evolutionand Reduction Reactions

The development of nonprecious metal bifunctional catalysts capable of catalyzing both the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) has become important for metal–air regenerative batteries. Metal–organic framework (MOF)-derived materials, such as oxides, sulfides, phosphides, etc., offer a facile approach to designing porous, cost-effective bifunctional catalysts. In this study, we report the synthesis of MOF-derived amorphous cobalt–vanadium oxide supported on multiwalled carbon nanotubes (MWCNT), represented as CV@MWCNT, through a facile hydrothermal and calcination process. The OER and ORR activities of CV@MWCNT surpass those of cobalt–vanadium oxide on MWCNT synthesized directly from metal precursors. Various compositions of CV@MWCNT, along with control samples, were synthesized and characterized using physicochemical, spectroscopic, and electrochemical techniques. The optimal composition, Co:V = 2:1 (CV21@MWCNT), shows an OER overpotential of 337 mV at 10 mA.cm^–2. The ORR onset potential (E_onset) and half-wave potential (<i>E</i>_1/2) were determined to be 0.92 and 0.80 V vs RHE, respectively. Notably, the potential gap (Δ<i>E</i>) for CV21@MWCNT was 0.76 V outperforming the state-of-the-art RuO₂/(Pt/C) catalyst pair (Δ<i>E</i> = 0.80 V).