Design of BDD-TiO2 hybrid electrode with P-N function for photoelectroatalytic degradation of organic contaminants.

P-N hybrid electrode of boron-doped diamond (BDD) and TiO2 were designed and fabricated via selective deposition of TiO2 onto BDD electrode. This hybrid electrode exhibit high photoelectrocatalytic activities toward degradation of acid orange II (AOII) and 2, 4-dichloropheonl (2,4-DCP) due to the P-N effect and high electrocatalytic and photocatalytic activities of BDD electrode and TiO2 particles. The structures of TiO2 and BDD were confirmed by Raman spectra analysis. Atom force microscopy and scanning electron microscopy showed that the TiO2 deposits consist of adherent nanomicro-sized particles, scattered on the BDD substrate. AOII and 2,4-DCP in a solution can be efficiently degraded at the hybrid electrode in the photoelectrocatalysis (PEC) process. Effect of applied bias potentials and solution pH values on AOII and 2,4-DCP degradation were investigated. In the electro-oxidation process, some intermediates such as phenols were detected and they accumulated with the reaction evolution based on the analysis of UV-vis and GC-MS variation. By contrast, phenols intermediates will be degraded with the reaction evolution in the photoelectrocatalysis process. And, organic aromatic and aliphatic carboxylic acids were detected. Furthermore, different degradation mechanism of AOII and 2,4-DCP in the electro-oxidation, photocatalysis, and photoelectrocatalysis is proposed.