Carbon nanostructures embedded with bimetallic CoRu alloy nanoparticles as oxygen reduction electrode for zinc-air batteries

We synthesized CoRu bimetallic nanoparticles with varying metal contents (Co : Ru: 3 : 1, 1 : 1, and 1 : 3) embedded in a graphitized carbon framework and used them as electrocatalysts. Benefiting from the porous nature of the carbon structure, which exposes a large number of active centers and the synergy with bimetallic nanoparticles, the catalysts exhibit excellent performance for both oxygen evolution and reduction reactions (OER/ORR). The catalyst CoRu@C (with a 1 : 1 metallic ratio) introduces a strong synergistic effect between alloy nanoparticles and the carbon layer, enhancing its catalytic activity compared to the other catalysts. This CoRu@C sample exhibits a low overpotential (eta 10) of 310 mV surpassing that of RuO2 (360 mV) for the OER and a half-wave potential (E1/2) of 0.838 V vs. the reversible hydrogen electrode (RHE), which is comparable to that of Pt/C (0.845 V) for the ORR in 0.1 M KOH. For practical feasibility, the fabricated Zn-air battery using this CoRu@C catalyst exhibits a higher open circuit voltage (OCV) of 1.461 V, surpassing that of Pt/C + RuO2 (1.443 V) and achieves a peak power density of 201.3 mW cm-2, outperforming Pt/C + RuO2 (138.1 mW cm-2). The ex situ characterization conducted at each 50 hour interval over the 250 hour cycling period demonstrates the robust nature of CoRu@C. This study provides a new avenue for designing efficient nanostructures for energy storage and conversion.