Enhancement of the photoelectrocatalytic degradation rate of a pollutant in the presence of a supercapacitor

Biochar was obtained by pyrolysis of spent malt rootlets and further treated with potassium hydroxide at 850 °C. The specific surface area of this biochar reached 1148 m2g-1, while the specific surface area of the micropores became 690 m2g-1. This biochar was used to make a supercapacitor electrode by depositing biochar particles on a carbon cloth and by immerging the electrode in a sodium sulfate aqueous electrolyte. The supercapacitance under the present conditions was 85 Fg-1. This electrode was introduced as a third electrode in a photoelectrochemical cell based on a semiconductor photoanode. A visible-light absorbing photocatalyst was obtained by combining titania with cadmium sulfide. Methylene blue was used as a model pollutant in order to study its photoelectrocatalytic degradation in the presence of the biochar. An impressive increase of the rate of dye removal from the aqueous solution has been observed, resulting to 60% increase under continuous illumination and 300% increase under intermittent light supply. This is attributed to the dual property of the biochar to act as strong adsorber of the dye and as a supercapacitor.