Hetero-interfacial nickel nitride/vanadium oxynitride porous nanosheets as trifunctional electrodes for HER, OER and sodium ion batteries

Abstract

The development of single electrode with multifunctional purposes for electrochemical devices remains a symbolic challenge in recent technology. This work explores interfacially-rich transition metal nitride hybrid that consist of nickel nitride and vanadium oxynitride (VO0.26N0.52) on robust carbon fiber (denoted CF/Ni3N/VON) as trifunctional electrode for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and sodium ion batteries (SIBs). The as-prepared CF/Ni3N/VON exhibits low HER overpotential of 48 mV@10 mA cm−2, OER overpotential of 287 mV@10 mA cm−2, and sodium-ion anode storage reversible capacity of 555 mA h g−1@0.2 C. Theoretical analyses reveal that the Ni3N effectively facilitates hydrogen desorption for HER, increases the electrical conductivity for OER, and promotes the Na-ion storage intercalation process, while the VON substantially elevates the water dissociation kinetics for HER, accelerates the adsorption of OH* intermediate for OER and enhances the Na-ion surface adsorption storage process. Owing to the excellent HER and OER performances of the CF/Ni3N/VON electrode, an overall water splitting device denoted as CF/Ni3N/VON//CF/Ni3N/VON was not only assembled showing an operating voltage of 1.63 V at current density of 10 mA cm−2 but was also successfully self-powered by the assembled CF/Ni3N/VON//CF/Na3V2(PO4)3 flexible sodium ion battery. This work will contribute to the development of efficient and cost-effective flexible integrated electrochemical energy devices.