BiPO 4 -coated carbon microtube electrodes: preparation and characterization of their properties and electrocatalytic degradation of methylene blue.

Bismuth phosphate (BiPO 4 ), 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 BiPO 4 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 5.71 mA cm -2 at a potential of 1.6 V vs Ag/AgCl. The electrochemical impedances and actual lifetime of BCC4 were 125 Ω and 833 h, respectively. The effectiveness of each kind of BiPO 4 /carbon electrode was preliminarily evaluated by analyzing the actual conversion rate of the MB concentration, which confirms MB electrodegradation by the BiPO 4 /carbon electrode was mainly dominated by the hydroxyl radical oxidation. The mass transfer rate was increased by carbon microtube; thereby, electrocatalysis of BiPO 4 /carbon electrode increased as revealed by an increase in the MB degradation rate. The rate constants k obtained for the degradation of MB by BiPO 4 /carbon electrode at 20 ℃ was 0.0046 mM -1  s -1 , which was 11 times than that of BiPO 4 . The diffusion layer was decreased by carbon microtube, resulting in MB electrodegradation rate increased. The BiPO 4 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, BiPO 4 /carbon electrode could be potentially applied in the electrodegradation of organic pollutants.