Synergistic Regulation of Triple-Phase Interfaces and Mass Transfer via Structure Engineering for High-Performance Oxygen Electrocatalysis

The slow oxygen mass transfer and limited active-site availability at triple-phase interfaces in the air electrode hinder the high-power-density output for Zn-air batteries (ZABs). The development of synergistic optimization strategies to address these issues is critical yet challenging. Herein, we construct NiCu alloy nanoparticles (NPs) on a mesoporous-rich N-doped carbon substrate (Ni_0.67Cu_0.33/meso-NC) as the electrocatalyst to enlarge the micro-triple-phase interface in the catalyst layer of the air electrode. Benefiting from the mesoporous structure, Ni_0.67Cu_0.33/meso-NC shows good ORR activity (<i>E</i>_1/2 = 0.883 V, <i>j</i>_L = 5.83 mA cm^-2), higher than its nonmesoporous counterpart and commercial Pt/C. Electrochemical analysis confirms the more accessible triple-phase interface active sites and accelerates the mass transfer for engineered mesoporosity in catalysts during the ORR process. In air electrodes of ZABs, a mesoporous architecture can serve as "highways" among the catalyst layers to promote oxygen diffusion and enrichment at active sites while simultaneously optimizing the specific surface area and hydrophobic/aerophilic characteristics to increase the accessible triple-phase interfaces and alleviate active-site blockage. These synergistic effects enhance the discharge performance and power density of ZABs. Consequently, the resulting Ni_0.67Cu_0.33/meso-NC-based liquid ZAB achieves a high peak power density of 232.6 mW cm^-2 and stable operation for 400 h without obvious voltage decay. This study offers a synergistic regulation strategy of mesoporous catalysts and air electrodes for high-performance metal-air batteries.