Enhancement of electrooxidation activity of activated carbon for direct carbon fuel cell

Direct carbon fuel cells are promising power sources using solid carbon directly as fuel. Their performances significantly depend on the electrooxidation activity of carbon fuel. Electrooxidation of activated carbon particulates in molten Li₂CO₃–K₂CO₃ was investigated by potentiodynamic and potentiostatic method. Results indicated that the electrooxidation performance of activated carbon was significantly enhanced by pre-soaking with Li₂CO₃–K₂CO₃ and by treatment with HF, HNO₃ and NaOH, respectively. The onset potential negatively shifted by around 100 mV and the current density increased by around 50 mA cm⁻² after pre-soaking. The non-oxidant acids (HF) treatments are more effective than oxidant acid (HNO₃) and base (NaOH) treatments. HF treated activated carbon exhibited the highest activity among all the samples. The enhancement in electrooxidation performance can be closely correlated with the increase in surface area and porosity caused by acid and base treatments.