Copper-hybridized lignin-derived carbon nanotube as a supercapacitor electrode material

Advances in supercapacitor energy storage rely on innovations in electrode materials. Although hybrid carbon materials provide large surface areas and abundant active sites, they often suffer from limited conductivity and cycling stability. Metal oxide composites introduce Faradaic pseudocapacitance but face challenges in achieving uniform dispersion and scalable green synthesis. Here, we report a copper-hybridized lignin-derived carbon nanotube (Cu@LCNT) nanocomposite synthesized from renewable sodium lignosulfonate and copper chloride. The Cu@LCNT exhibits uniformly distributed cuprous oxide and copper nanoparticles that enhance conductivity and contribute pseudocapacitance. It delivers a high specific capacitance of 847.9 F/g at 0.5 A/g. The capacitance retention reaches 107.3% after 10,000 cycles. The slight increase above 100% retention arises from an activation process that improves electrode-electrolyte contact and exposes additional active sites during cycling. This study demonstrates a sustainable and efficient approach to designing metal-carbon nanocomposites from biomass resources for high-performance supercapacitor electrodes.