Electronic Reallocation in MOF-Derived Co<sub>4</sub>N–Ni<sub>3</sub>N Heterostructure Renders Chlorine-Free Overall Seawater Splitting under Large Current Density
Rajdeep Kaur, Ashish Gaur, Aashi, Vikas Pundir, Jatin Sharma, Chandan Bera, Vivek Bagchi
Abstract
As a viable method, electrocatalytic water splitting for hydrogen production, particularly in seawater, appears to be an appealing technique. Herein, the Co 4 N–Ni 3 N heterostructure was derived by controlled nitridation of a bimetallic NiCo-based metal–organic framework. The Co 4 N–Ni 3 N heterostructure shows a very low overpotential of 330 and 319 mV at a very high value of 500 mA cm –2 in alkaline freshwater for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, and can perform at a very large current density of nearly 1.2 A cm –2 for the OER and 1 A cm –2 for the HER. Since the overpotential is less than the limit of the chlorine evolution reaction, it provides a potential platform for chlorine-free OER for seawater electrolysis. The Co 4 N–Ni 3 N catalyst exhibits exceptional durability, maintaining stability for over 230 h at 500 mA cm –2 in the OER and 100 h at 500 mA cm –2 in the HER without experiencing significant loss in the activity. For total water decomposition, Co 4 N–Ni 3 N shows a cell potential of 1.97 and 2.19 V at 500 mA cm –2 in 1 M KOH and simulated seawater, respectively. This enhanced heterostructure activity is due to a synergistic impact caused by the in situ development of the interface between Co 4 N and Ni 3 N phases during the controlled nitridation process.