One-Step Synthesis of Ni/NiO Nanoparticles on Nitrogen-Doped Carbon Foam as Bifunctional Electrocatalysts for Oxygen Reduction and Oxygen Evolution Reactions

The development of effective bifunctional electrocatalysts for the oxygen reduction (ORR) and evolution (OER) reactions is crucial for advancing electrochemical technologies. However, the high cost and scarcity of noble metals present a significant challenge for the widespread application of these reactions. To address this, we synthesized a novel Ni and NiO nanocomposite on nitrogen-doped carbon foam (Ni and NiO/N-CF) via a single-step pyrolysis of urea, glucose, and a nickel salt in NaCl salt as a templet. The resulting catalyst, which displayed cubic crystalline Ni and NiO nanoparticles, was thoroughly characterized using a variety of physical and chemical methods. The Ni and NiO/N-CF catalyst demonstrates promising OER performance, with an overpotential of 300 mV (at 10 mA cm^–2), a Tafel slope of 86.2 mV dec^–1, and an electrochemical active surface area of ∼45 cm² g^–1, maintaining activity for over 60 h. The catalyst is also effective for ORR, exhibiting a half-wave potential of 0.78 V vs RHE and a Tafel slope of 80 mV dec^–1 in KOH. The bifunctional overpotential of the Ni and NiO/N-CF composite has a minimal potential difference (ΔE) of 820 mV, comparable to that of benchmark catalysts (10% Pt/C for ORR and IrO₂ for OER, combined: 680 mV), highlighting its potential for zinc- air practical applications.