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

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 (de-noted 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 overpo-tential 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 stor-age 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 stor-age 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 oper-ating 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. (c) 2023 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).