Wood-derived carbon electrode modified with sulfuric acid-dispersed graphene oxide for high-performance supercapacitors

Nowadays, wood has gained popularity in the field of energy storage due to its availability, renewability and environmental friendliness. The original hierarchical porous structure of wood can be well preserved after carbonization, and carbonized wood (CW) exhibits excellent electrical conductivity and low curvature. This makes CW suitable for direct use as both an active material and a current collector in supercapacitors. However, the pore size of CW is relatively large, leading to inefficient use of pores space and limiting the number of active sites, thus reducing its specific capacity. To optimize the utilization of CW's channel space, we investigated the filling of its channels with reduced graphene oxide (RGO) and prepared the RGO@CW electrode. To prevent RGO stacking and aggregation within the CW channels, sulfuric acid was added to the graphene oxide (GO) impregnation solution, and investigated the effects of varying sulfuric acid concentrations on the electrochemical performance of the produced electrode. The prepared HRGO/CW-1 electrode demonstrated an area specific capacitance of up to 4680 mF cm⁻² at a current density of 5 mA cm⁻². The assembled symmetric supercapacitors (SSCs) exhibited excellent energy densities in both neutral and alkaline systems, reaching 12.12 Wh kg⁻¹ (0.85 mWh cm⁻²) and 3.35 Wh kg⁻¹ (0.23 mWh cm⁻²), respectively. Moreover, the SSCs maintained 97.6 % of their capacity after 20,000 cycles in a 1 M Na₂SO₄ electrolyte, indicating their excellent cycle stability. This study not only enhances the understanding of wood as an energy storage medium, but also provides valuable insights for sustainable energy storage solutions.