Design of VN anode catalyst towards enhanced kinetics for vanadium flow batteries

The all-vanadium flow battery (VFB) constantly suffers from sluggish kinetics for the negative electrodes, restricting its operation ability at high current density. To develop an effective catalyst for anode materials, vanadium nitride (VN) is synthesized to decorate the carbon felt (VN-CF). The unique 1-dimension structure and mesoporous character of VN nanorods are beneficial to the mass transfer in the liquid phase. More importantly, by DFT calculation, VN demonstrates strong adsorption energy to the hydrated vanadium ions, thus effectively shortening the distance between reactants and the electrode and accelerating the electron transfer process, which could significantly improve the electrochemical kinetics, from the perspective of the classical electric double layer model theory. As a result, the VN-CF anode exhibits an energy efficiency up to 72.17% at a high current density of 200 mA cm−2, 3.84% higher than the pristine carbon felt electrode. Additionally, the VFB equipped with VN-CF electrode demonstrates superior cycling stability and high-capacity retention. This work provides an innovative idea to uncover the underlying catalytic mechanism of VN, which can also guide the research direction for the high-performance electrocatalyst of VFB in the future.