BiPO4-coated carbon microtube electrodes: preparation and characterization of their properties and electrocatalytic degradation of methylene blue.

Abstract

Bismuth phosphate (BiPO4), a very attractive candidate for organics electrodegradation, harbors tremendous potential on removing contaminants from water. Here, four carbon microtube electrodes were prepared from corncob, each coated with BiPO4 by a different method to study the electrodegradation of methylene blue (MB). A thorough insight into the composite features of four electrodes was characterized. Better reversibility and electrocatalytic activity of the fourth electrode (BCC4) prepared by digital signal generator was presented with a current density of 5.71mAcm-2 at a potential of 1.6V vs Ag/AgCl. The electrochemical impedances and actual lifetime of BCC4 were 125Ω and 833h, respectively. The effectiveness of each kind of BiPO4/carbon electrode was preliminarily evaluated by analyzing the actual conversion rate of the MB concentration, which confirms MB electrodegradation by the BiPO4/carbon electrode was mainly dominated by the hydroxyl radical oxidation. The mass transfer rate was increased by carbon microtube; thereby, electrocatalysis of BiPO4/carbon electrode increased as revealed by an increase in the MB degradation rate. The rate constants k obtained for the degradation of MB by BiPO4/carbon electrode at 20℃ was 0.0046mM-1s-1, which was 11 times than that of BiPO4. The diffusion layer was decreased by carbon microtube, resulting in MB electrodegradation rate increased. The BiPO4 coated on the surface of the carbon microtube electrodes strengthened their electrocatalytic performance, which shed new light on effective selection of suitable carbon electrode for degradation of organics. Therefore, BiPO4/carbon electrode could be potentially applied in the electrodegradation of organic pollutants.