NiFe-coordinated zeolitic imidazolate framework derived trifunctional electrocatalyst for overall water-splitting and zinc-air batteries.

Developing high-efficient non-noble metal electrocatalysts toward oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), water-splitting, and the zinc-air battery is essential but challenging. Zeolitic imidazole frameworks (ZIFs) are generally employed as ideal platforms for the design and fabrication of energy-related catalysts by exploiting their porous structure with high surface area and flexibility. This work presents the preparation of NiFe-bimetallic species decorated N-doped porous carbon composite (NiFe@NPC) through pyrolyzing the NiFe-coordinated ZIF precursor. The obtained NiFe@NPC shows a larger surface area and porous nanostructure comprising the active bimetallic species evenly distributed in the conductive carbon matrix. The nanocomposite demonstrates excellent trifunctional catalytic activity toward ORR, OER, and HER. For ORR, NiFe@NPC offers a half-wave potential value of 0.87 V, which is positively shifted by 30 mV relative to that of Pt/C in 1 M KOH. NiFe@NPC exhibits OER activity with superior overpotential, reaction kinetics, and durability to those of IrO. It also demonstrates the desirable HER activity with a low overpotential of 150 mV at 10 mA/cm and excellent durability in an acidic electrolyte. Additionally, the water-splitting configuration and zinc-air battery assembled with NiFe@NPC catalyst reveal superior performance to noble-metal catalysts. Such excellent electrocatalytic performance can be attributed to the distinct chemical composition of evenly distributed bimetallic active sites on highly conductive carbon sheets, and the porous nanostructure with large surface area and fast mass transfer.