A unique hybrid of vanadium carbide and oxycarbide derived carbon from a preceramic polymer route with faradaic and supercapacitive charge storage

Polymer-derived ceramics are a versatile class of multifunctional materials synthesized <i>via</i> the high-temperature treatment of a preceramic polymer. In this work, we report the synthesis of a vanadium carbide-embedded carbonaceous hybrid by pyrolyzing a modified preceramic polymer incorporating vanadium acetylacetonate in a polysilsesquioxane followed by hydrofluoric acid etching. The structural and microscopic characterisation confirmed the uniform distribution of nanoparticulate vanadium carbide in the matrix. Electrochemical behaviour was analyzed in a three-electrode set-up in sodium sulfate electrolyte, which exhibited a unique combination of supercapacitive and faradaic charge storage mechanisms. The broad redox peak found around -0.4 V suggested the presence of a faradaic charge storage mechanism, whereas the current across the entire potential range indicated supercapacitive behaviour. The material exhibited a specific capacitance of 123.7 F g^-1 at a scan rate of 20 mV s^-1. The high point of this work is that the specific capacitance of the hybrid did not deteriorate even at a high potential scan rate of 100 mV s^-1. The solution resistance (<i>R</i>₁) and charge transfer resistance (<i>R</i>₂) were found to be approx. 2.8 Ω and 3.1 Ω, respectively. The frequency, potential, and complex capacitance relationship with the charge storage mechanism was elucidated by the 3D graphical analysis of the Bode plot. Furthermore, a symmetric supercapacitor fabricated from the developed hybrid demonstrated robust cyclability, retaining 78% of its initial capacitance after 5000 cycles. The device achieved an energy density and power density of 254 Wh kg^-1 and 58 W kg^-1, respectively, with a coulombic efficiency of 95% at the end of cycling. This study demonstrates an innovative approach for the synthesis of a hybrid material from the preceramic polymer route with faradaic and supercapacitive charge storage mechanisms.