Incorporation of RuO₂ into charcoal-derived carbon with controllable microporosity by CO₂ activation for high-performance supercapacitor

The use of metal oxides in carbon-based supercapacitors (SCs) is regarded as an efficient strategy to obtain enhanced capacity. However, the poor cycle stability of pseudocapacitive metal oxides and the low capacitance of carbon-based materials limit the performance of SC. In this work, charcoal-derived activated carbon (CAC) is obtained by KOH activation and CO₂ activation of various durations, and RuO₂/CAC is fabricated by a hydrothermal route. The resulting materials yield improved performance. A series of characterizations, including X-ray diffraction measurement, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller analysis, and contact angle measurement prove that RuO₂ nanoparticles are uniformly dispersed on the surface of the as-prepared CAC. Three-dimensional hetero-RuO₂/CAC exhibits high conductivity owing to efficient electron transport and abundant active sites, leading to enhanced supercapacitor performance. A moderate pore size distribution is found to yield optimal electrochemical activity. The as-prepared composites obtained by CO₂ activation for 120 min generate high capacitances of 510 and 402 F/g at current densities of 1 and 20 A/g, respectively, with good stability (87.05% after 3000 cycles).