Prussian Blue Analogues Derived Bimetallic CoNi@NC as Efficient Oxygen Reduction Reaction Catalyst for Mg-Air Batteries

The magnesium-air (Mg-air) batteries are regarded as a highly promising system for electrochemical energy conversion and storage, owing to their exceptional energy density, notable safety and eco-friendliness. The development of high-performance and durable non-noble metal catalysts for the cathodic oxygen reduction reaction (ORR) is crucial for advancing the practical use of Mg-air batteries. The synergistic interaction between different metals in bimetallic catalysts is an effective strategy for enhancing the activity and stability of the catalysts. Herein, various prussian blue analogues (PBA) were selected as precursors to synthesis the bimetallic CoNi@NC, monometallic Co@NC and Ni@NC catalysts due to tunable chemical compositions. Compared with Co@NC and Ni@NC, the bimetallic CoNi@NC pyrolyzed at 600 degrees C (CoNi@NC-600) exhibits outstanding ORR performances and stability in alkaline (0.1 M KOH) and neutral (3.5 wt % NaCl) electrolytes. Following 5000 CV cycles, the half-wave potentials for CoNi@NC-600 show only minor negative shifts of 8 and 7 mV, respectively. Meanwhile, the CoNi@NC-600 possesses the similar ORR reaction mechanism and activity with Pt/C. The primary Mg-air battery assembled with CoNi@NC-600 displays better discharge performances than that of Co@NC and Ni@NC. This study lays the foundation for future investigations into the advancement of non-precious bimetallic catalysts for ORR in Mg-air batteries.