MXene-SnO₂ modified carbon felt electrode for enhanced performance in vanadium redox flow batteries

Metal oxide catalysts offer low cost, strong activity, and structural diversity, but their use in vanadium redox systems is limited by poor conductivity and small surface area. This study developed a MXene-SnO₂ composite electrode using a hydrothermal technique, followed by thermal annealing, and investigated its electrocatalytic activity in vanadium redox flow battery systems. MXene, a two-dimensional transition metal carbide, was chosen as a conductive support because of its high electrical conductivity, hydrophilicity, and abundance of surface functional groups. These properties enhance rapid electron transport and provide an accessible surface for vanadium ion interactions. SnO₂ nanoparticles, known for catalytic activity and wettability, were uniformly spread over the MXene surface, contributing to better redox and charge transfer processes. The composite demonstrated enhanced electrocatalytic activity for both VO²⁺/VO₂⁺ and V²⁺/V³⁺ couples compared with individual components. The synergistic action of MXene and SnO₂ enhances ion diffusion, electron transport, and interfacial charge transfer. Cell tests confirmed higher electrolyte performance and reduced polarization. At a current density of 100 mA/cm², the energy efficiency reached 85 %, a 5 % increase from the bare electrode. These findings suggest that mixing MXene and metal oxides is an excellent technique for creating high-performance electrocatalysts for vanadium redox flow batteries.