Co/Fe3O4 nanoparticles embedded in N-doped hierarchical porous carbon derived from zeolitic imidazolate frameworks as efficient oxygen reduction electrocatalysts for zinc–air battery-based desalination

Abstract

Zinc–air battery-based desalination (ZABD) is a potential solution to effectively desalinate brackish water and supply energy simultaneously, which requires catalysts with high and durable electrocatalytic activity for the oxygen reduction reaction (ORR) on the cathode of zinc–air batteries. Herein, a N-doped hierarchically porous carbon material encapsulating Co/Fe₃O₄ nanoparticles was successfully prepared using zeolitic imidazolate framework-8 (ZIF-8) as the precursor. Due to the integration of large specific surface area, hierarchically porous structure, and Co/Fe₃O₄ nanoparticles, the Co/Fe₃O₄@ZIF-8C catalyst exhibits a limiting current density of 5.93 mA cm⁻² and a half-wave potential of 0.83 V, which is comparable to that of commercial platinum/carbon (Pt/C). It also presents outstanding durability and methanol endurance, superior to the Pt/C catalyst. More importantly, Co/Fe₃O₄@ZIF-8C achieved the dual functions of a fast salt removal rate (32.9 μg cm⁻² min⁻¹) and high energy output (91.6 KJ mol⁻¹) when employed as the cathode catalyst of ZABD, which can process brine of 3000 ppm to a drinking water level of 128 ppm. The employment of Co/Fe₃O₄@ZIF-8C enables ZABD to possess stable batch cyclability and durable desalination performance. This is the first time that a non-noble metal catalyst has been applied in ZABD, realizing an outstanding desalination performance comparable to that of commercial Pt/C. Accordingly, the high-efficiency and low-cost ORR catalytic material provided by this work has significant application prospects in seawater desalination and metal–air discharge batteries.