Enhanced Oxygen Evolution Reaction Performance of Niobium–Cobalt Oxide Catalysts in Acidic and Alkaline Media

Designing and achieving active and stable oxygen evolution reaction (OER) catalysts for both acidic and alkaline media is essential but challenging. Herein, we are reporting Nb-doped Co3O4 catalys synthesized via hydrothermal route. The optimized CoNb0.6 catalyst showcases an overpotential of 260 and 250 mV at 10 mA cm−2 for the OER in 1 M KOH and 0.5 M H₂SO₄, respectively, significantly lower than that of Co₃O₄, which requires 440 and 310 mV under the same conditions. Nb doping significantly enhances the electrochemically active surface area (ECSA) and charge transfer kinetics of CoNb0.6 exhibiting a 7.8-fold and 10-fold increase in ECSA in 1 M KOH and 0.5 M H₂SO₄, respectively. The catalyst can operates at a current density of 10, 30, and 100 mA cm−2 for over 35 h under 1 M KOH, but it operates for ≈80 h at a current density of 10 and 50 mA cm−2 under 0.5 M H2SO4. The higher activity emanated from the synergistic effect between the Nb5+ dopant and Co3O4. Whereas the long-term durability emanates from the formation of Nb5+ in Co3O4 during OER suppresses dissolution of Co and strengthens the Co─O bonds in Co3O4 to prevent the formation of soluble high-valent Nb species.