A novel composite hard carbon from waste Camellia oleifera shell modified by phenol-formaldehyde resin for supercapacitor electrode with high specific capacitance

Abstract

The lower specific capacitance of biochar electrode material limits its practical application. Therefore, this study attempts to develop a novel supercapacitor biochar electrode material with high specific capacitance from waste camellia oleifera shell (COS). COS shell powder was pre-impregnated with phenol-formaldehyde (PF) resin then carbonization-KOH activation. An orthogonal experiment (L9(33)) was designed to explore the influence of mass mixing ratio of PF/COS, activation time, and temperature on the electrochemical property of COS-based biochar. The optimal process parameters were: 800 °C, 1 h and mass mixing ratio of 5:1. Compared with c. oleifera shell-activated carbon (COS-AC) and phenol-formaldehyde-activated carbon (PF-AC) controls, the phenol-formaldehyde modified c. oleifera shell-activated carbon (PMC-AC) exhibited micro-morphology of carbon microspheres and a three-dimensional network pore. The internal orientation of PMC-AC tended to be disordered, and had a superior specific surface area of 3037.68 m2 g−1 and total pore volume of 1.7 cm3 g−1. Electrochemical tests used PMC-AC as the negative electrode, with high specific capacitance (375.9 F g−1 at 0.5 A g−1), good rate property (49.3 % of capacitance retention at 0.5–10 A g−1), and charging/discharging stability. It is supposed that it was a convenient and feasible way to modify biochar into high-quality hard carbon for supercapacitors.