Pretreated mesocarp fibre biochars as carbon fuel for direct carbon fuel cells

This work focuses on the effect of acid and alkali pretreatment of palm mesocarp fibre (PMF) on its fuel performance in a direct carbon fuel cell (DCFC). PMF is pretreated with acid and alkali in the range of 0.1 M–4 M and followed by pyrolysis to produce biochar fuel. Performance is evaluated in the DCFC at 750 °C, 800 °C, and 850 °C. This work reveals that 2.0 M HCl treated PMF biochar gives the lowest ash value (0.1 wt%) and the highest O/C ratio among all tested biochars. The acid pretreatment contributes to enhanced electrochemical reactivity of the PMF biochar, which gives a peak power density output of 11.8 mW cm⁻² at 850 °C in the DCFC. This obtained peak power density is higher than the power density of untreated biochar, recorded at a value of 0.70 mW cm⁻². The results indicate that reduced ash, the existence of oxygen functional groups, and porous fibrous structure have increased the electro-oxidation active sites of the pretreated biochar fuel in DCFC.