Enhanced electrochemical performance of porous carbon from wheat straw as remolded by hydrothermal processing

To improve the electrochemical properties of lignocellulose-derived carbon, wheat straw was hydrothermally processed at different temperatures followed by KOH activation for the preparation of porous carbons. Their physical, chemical, and electrochemical properties were analyzed to clarify the effects of hydrothermal processing. The results indicated that high-temperature hydrothermal processing fragmented the wheat straw and increased the heteroatoms content to make the hydrochars more conducive to activation, thereby improving the specific surface area, N-heteroatoms and phenolic hydroxyl groups of activated carbons. A maximum specific surface area of 2034.4 m² g^-1 was achieved by HAC-300 (the activated carbon derived from hydrothermally processed wheat straw at 300 °C) with more N-heteroatoms and phenolic hydroxyl groups. Correspondingly, the excellent electrochemical performance of the three-electrode supercapacitor device assembled by HAC-300 showed a specific capacitance of 286.95 F g^-1 at 0.5 A g^-1, representing an improvement of 89.5 % over than that of the original wheat straw without hydrothermally processing. Its symmetric supercapacitor also realized a good capacitance retention of 95.8 % after 10,000 cycles at 5 A g^-1, suggesting the excellent cycling stability of the porous carbon from the hydrothermally processed wheat straw.