Bridging the charge gap: Nb2CTx/Nb2O5 Schottky heterojunctions as electronic highways in vanadium redox flow battery

Vanadium redox flow battery (VRFB), as a potential technology for next-generation energy storage system, is restricted by the slow redox kinetics of vanadium ions. Implementing interface engineering strategies to functionalize the surface of MXene can effectively address this challenge. Herein, a Nb 2 CT x /Nb 2 O 5 Schottky heterostructure is constructed to facilitate high-speed charge transfer at the VRFB electrode through controllable in-situ oxidation. The loading amount of Nb 2 O 5 nanorods on the surface of Nb 2 CT x nanosheets was regulated by varying the hydrothermal reaction time. Density functional theory calculations confirm that the Schottky barrier formed between Nb 2 CT x and Nb 2 O 5 leads to the establishment of an internal electric field and reconfigures the electronic structure of surficial active sites. The rich pore structure of Nb 2 CT x /Nb 2 O 5 electrode effectively shortens the diffusion path for vanadium ions, while its excellent hydrophilicity enhances the interaction between vanadium ions and the electrodes. Compared with graphite felt, Nb 2 CT x /Nb 2 O 5 -2@GF cell shows a 20% increase in energy efficiency (EE) at 150 mA cm −2 cycling, reaching 75%, while maintaining stable performance for over 800 cycles. This means a significant advancement in the development of high-performance electrodes for VRFBs. This work offers an efficient and scalable strategy for the design of redox flow batteries.