Heterointerface engineering of uniformly dispersed MnCo₂O₄ nanoparticles on α-MnO₂ nanotubes as efficient oxygen reduction reaction electrocatalysts

The exploration of non-precious metal catalysts (NPMCs) with high activity and excellent stability for the oxygen reduction reaction (ORR) is significant to develop the fuel cells and metal-air batteries (MABs) for large-scale applications. Heterointerface engineering is deemed as a prospective strategy to improve the ORR activity by modulating the inner electronic structure and enhancing the surface properties. Herein, the uniformly dispersed MnCo₂O₄ nanoparticles on α-MnO₂ nanotubes were fabricated via a two-step route, and the nanoparticle size was regulated at different calcination temperatures to obtain MnCo₂O₄/α-MnO₂ catalysts (MCM-T, T = 450 ℃, 600 ℃, 750 ℃, 900 ℃). Benefiting from the large specific surface area, hierarchical porous structure and high ratio of (Mn³⁺+Mn⁴⁺)/Mn²⁺, the MCM-450 catalyst exhibits superior ORR activity with a half-wave potential of 0.78 V (vs. RHE) and remarkable stability in 0.1 M KOH solution. Correspondingly, an impressive specific capacity (875.6 mAh g⁻¹), a high discharge plateau (1.37 V) and a noticeable peak power density (151.1 mW cm⁻²) are achieved in MCM-450-based liquid aluminum-air batteries (LAABs), surpassing the performance of the commercial 20 wt% Pt/C catalyst (601.0 mAh g⁻¹, 1.31 V, and 128.2 mW cm⁻²). This work provides a new strategy on developing transition metal oxides (TMOs) catalysts and endows an opportunity for efficient sustainable energy storage.