RuO₂-decorated Cs_xWO₃ composite nanorods as transparent photothermal negative electrode material for enhancing supercapacitor performance in acid electrolyte

With the development of wearable and portable electronics, flexible transparent photothermal supercapacitors which improve the performance via the utilization of sunlight have received increasing attention. The high performance electrode materials, particularly those for negative electrodes in acid electrolytes, are needed. Herein, we developed a novel flexible transparent photothermal supercapacitor using RuO₂-decorated Cs_xWO₃ nanorods as the negative electrode material for acid electrolytes. It was demonstrated that the resulting electrodes possessed good pseudocapacitive performance in the potential window of −0.5–0.0 V in 1 M H₂SO₄ and the appropriate decoration of RuO₂ on Cs_xWO₃ nanorods could raise the pseudocapacitance effectively. Also, the fabricated all-solid-state supercapacitor was shown to possess high visible light transparency, flexibility, capacitive performance and stability. Its electrochemical performances could be remarkably enhanced by simulated sunlight illumination because the photothermal conversion-induced temperature increase might reduce the electrolyte and charge-transfer resistances effectively. Further kinetic analysis revealed that the enhanced capacitance was contributed by both the diffusion-limited and surface-limited processes. Accordingly, the strategy to improve the capacitive performance of Cs_xWO₃ nanorods by RuO₂ decoration was successful and made the resulting composite have great potential as the negative electrode material for transparent photothermal supercapacitors.