Electrocapacitive and electrocatalytic performances of hydrochar prepared by one-step hydrothermal carbonization without further activation

Hydrochar was produced from extracted avocado seed using one-step hydrothermal carbonization (HTC) at a temperature of 200 °C for 12 h. The effects of various feedstock solutions on the specific surface area, morphology, pore characteristics, crystallinity, and chemical bonding were investigated to confirm the changes in the electrochemical performances of the produced hydrochar. The presence of potassium permanganate (KMnO₄) and ammonia (NH₄OH) solution in the HTC process successfully produced a porous graphite-like structure of hydrochar with the highest surface area and specific capacitance. Moreover, it also exhibits excellent electrocatalytic performance toward the Oxygen Reduction Reaction (ORR), with a current density of 2.15 mA cm⁻² via the 2-electron pathway. These results imply that the HTC process can produce hydrochar with high electrocapacitive and electrocatalytic performances even without further activation at high temperatures.