Fe-doped MnO₂/NiCo₂O₄ as Bifunctional Electrocatalyst for Oxygen Evolution Reaction and Oxygen Reduction Reaction in Alkaline Electrolyte

The catalytic performance of spinel oxide NiCo₂O₄ for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) was investigated. It shows that NiCo₂O₄ synthesized via hydrothermal treatment at 90 ℃ followed by calcination at 350 ℃ exhibits excellent catalytic activity. Furthermore, Fe-doped MnO₂ (marked as Fe-M) was introduced as a modifier to further improve the performance of NiCo₂O₄. As expected, the 20% Fe-M hybrid catalyst (NiCo₂O₄ modified with 20 wt% Fe-M) displays the best ORR and OER catalytic activity. This is evidenced by its high OER current density of 265 mA cm⁻², high ORR current density of 220 mA cm⁻², low OER Tafel slope of 119 mV dec⁻¹, low ORR Tafel slope of 167 mV dec⁻¹. These exceptional results can be attributed to the synergistic effect between NiCo₂O₄ and Fe-M.

Based on synergistic effect, the 20% Fe-M hybrid catalyst exhibits the best catalytic activity for oxygen evolution reaction and oxygen reduction reaction.