Electrochemical Energy Storage Capacity of Surface Engineered Renewable Carbon Derived from Industrial Tea Waste by HNO₃ and K₂CO₃

Direct electrical energy storage by supercapacitors is the leading energy storage technology. The performance of supercapacitors depends mainly upon the electrode material constituents. Carbon is the preferred energy storage material for its some main properties such as a large surface area, electrical conductivity, porosity, thermal stability, etc. Sustainable, green, renewable, low-cost and environmentally friendly carbon energy storage materials can be obtained from biomass. A larger surface area and tunable micro-porosity, which are the most important advantages, could be achieved by chemical activation of K₂CO₃ and HNO₃. In this work, the effect of K₂CO₃ and HNO₃ on the porosity and the electrochemical energy storage capacity of carbon derived from biomass made from the industrial tea waste were evaluated. A carbon material with a high performance of energy storage exhibiting 460 F g^–1, with a surface area of 1261 m² g^–1, could be developed by activation of K₂CO₃ in the 1 : 1 optimum ratio (w/w). The HNO₃ treatment also increased the capacitance but to a very low degree.