Promoted Overall Water Splitting Catalytic Activity and Durability of NiFe Alloy by Designing N-Doped Carbon Encapsulation.

Combining an electrochemically stable material onto the surface of a catalyst can improve the durability of a transition metal catalyst, and enable the catalyst to operate stably at high current density. Herein, the contribution of the N-doped carbon shell (NCS) to the electrochemical properties is evaluated by comparing the characteristics of the NiFe@NCS catalyst with the N-doped carbon shell, and the NiFe catalyst. The synthesized NiFe@NCS catalyst has a distinct overpotential difference from the NiFe catalyst (η = 468.8 mV, η = 462.2 mV) at (200 and -200) mA cm in 1 m KOH. In stability test at (10 and -10) mA cm, the NiFe@NCS catalyst showed a stability of (95.47 and 99.6)%, while the NiFe catalyst showed a stability of (72.4 and 95.9)%, respectively. In addition, the in situ X-ray Absorption Near Edge Spectroscopy (XANES) results show that redox reaction appeared in the NiFe catalyst by applying voltages of (1.7 and -0.48) V. The decomposition of nickel and iron due to the redox reaction is detected as a high ppm concentration in the NiFe catalyst through Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) analysis. This work presents the strategy and design of a next-generation electrochemical catalyst to improve the electrocatalytic properties and stability.