Dual-metal synergy of bimetallic TiNbCTx MXene for enhanced poly(benzodifurandione)-based supercapacitor electrodes

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The conductive polymer poly(benzodifurandione) (PBFDO) combines good solution processability with high electrical conductivity, making it an attractive option for supercapacitor electrodes. Nevertheless, its tightly packed molecular chains and significant volume changes during cycling constrain both specific capacitance and cycling stability. Herein, bimetallic TiNbCT x MXene is introduced as a multifunctional modifier to tackle these challenges. The TiNbCT x component offers a dual-metal synergy: Ti sites ensure rapid electron transport, while Nb provides additional Nb 5+ /Nb 4+ redox-active centers and effectively modulates the local electronic environment of adjacent Ti atoms. Combined equal-loading controls, ex situ XPS, and DFT calculations suggest that Nb incorporation shifts the d -band center upward, strengthens interfacial adsorption, and promotes charge transfer, indicating a genuine synergistic effect beyond a simple additive function. After 20,000 cycles, the optimal composite with only 2 wt % TiNbCT x maintains 94.4% of its original capacitance while delivering 194.2 F g −1 at 0.5 A g −1 . Additionally, a constructed quasi-solid-state asymmetric supercapacitor (PBFDO/TiNbCT x //Ti 3 C 2 T x ) achieves 95.7% capacitance retention following 10,000 cycles, obtaining 21.4 Wh kg −1 at 350 W kg −1 . This work demonstrates that high-performance conductive polymer electrodes for improved energy storage can be achieved by bimetallic MXene engineering.