Bimetallic Co–Ni alloy nanoparticles loaded on nitrogen-doped wrinkled carbon nanospheres as high-performance bifunctional ORR/OER electrocatalyst in alkaline media

Preparation of an advanced bifunctional oxygen electrocatalyst is important for fuel cells, water splitting, etc. Herein, we report an oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) electrocatalyst with CoNi alloy nanoparticles uniformly distributed on nitrogen-doped carbon (N–C) nanospheres through a simple melamine-assisted pyrolysis strategy, in which a soft template approach is employed to prepare wrinkled N–C nanospheres. The Co₃Ni₁-N–C electrocatalyst exhibits higher onset potential (E₀ = 0.960 V vs. RHE (Reversible hydrogen electrode)), half-wave potential (E_1/2 = 0.81 V vs. RHE), and limiting diffusion current (j_L = 5.5 mA cm⁻²) for ORR. Meanwhile, Co₃Ni₁-N–C electrocatalyst has a lower overpotential of 0.360 V vs. RHE at 10 mA cm⁻² for OER, and a lower value for Tafel slope of 100 mV dec⁻¹, a potential difference between OER and ORR (ΔE = E_j=10-E_1/2) with a ΔE value of 0.779 V vs. RHE, which is close to the benchmark ΔE value of the combination of commercial noble metal catalysts (Pt/C-RuO₂, 0.744 V vs. RHE). In addition, Co₃Ni₁-N–C also shows remarkable stability, maintaining a relative current of 81.45% after 10 h at 0.8 V. The relative current of Co₃Ni₁ -N–C is also found to be stable, superior to commercial Pt/C by 34.5%. These excellent properties are due to its unique wrinkled structure, large surface area, and high content of CoNi-Nx and pyridine nitrogen active centers.