FeNi Nanoalloys Encapsulated in N-Doped CNTs Tangled with N-Doped Carbon Nanosheets as Efficient Multifunctional Catalysts for Overall Water Splitting and Rechargeable Zn-Air Batteries

The exploration of high-efficiency and cost-effective multifunctional electrocatalysts is of significant importance for future sustainable energy conversion and storage systems. Herein, 3D hybrid structures composed of OD FeNi nanoalloys embedded in 1D N-doped bamboo-like CNTs tangled with 2D N-doped carbon nanosheets (FeNi@N-CNT/NCSs) are rationally fabricated through a feasible carbonization strategy. Benefiting from the firmly N-doped carbon-wrapped FeNi nanoalloys as catalytic sites and hierarchically porous nanoarchitecture for efficient mass diffusion and electron transport, the fabricated FeNi@N-CNT/NCSs exhibit high multifunctional electrochemcial activities, comparable to that of noble-metal-based benchmarks, associated with impressive stability. It is indicated that the FeNi alloys evidently determine electrocatalytic activities, and the presence of FeNi alloys obviously improve long-term reaction stability. In addition, the atomic ratio of Fe to Ni in FeNi alloys can significantly affect the electrochemical performance toward oxygen evolution reaction, oxygen reduction reaction, and hydrogen evolution reaction. By using FeNi@N-CNT/NCSs as the anodic and cathodic electrocatalysts, an outstanding overall water splitting performance is obtained with the low cell potential and good durability in 1.0 KOH. The assembled Zn-air batteries with the FeNi@N-CNT/NCSs air cathode using the liquid-state and all-solid-state electrolyte exhibit the superior charging discharging performance, robust lifetime, and high flexibility, capturing the critical potential in actual implementation of metal air batteries with portable or wearable characteristics. This work will shed advanced inspiration for the fabrication of highly-efficient multifunctional catalysts for various energy technologies.