Novel Sieve-Like SnO2/TiO2 Nanotubes with Integrated Photoelectrocatalysis: Fabrication and Application for Efficient Toxicity Elimination of Nitrophenol Wastewater

A novel electrode with excellent photocatalytic (PC) and electrocatalytic (EC) performances was prepared by assembling sieve-like macroporous Sb-doped SnO2 (Mp-SnO2) film on vertically aligned TiO2 nanotubes (TiO2NTs) through a block copolymer soft-template method. The pore size of Mp-SnO2 ranges from 150 to 400 nm. The construction of the macropore can increase the specific surface area and provide more active sites. The band gap of the Mp-SnO2/TiO2NTs is 2.93 eV, and it presents outstanding light absorption and photoelectrochemical properties. Under the light irradiation of 365 nm, a high photoelectric conversion efficiency of 35.2% can be obtained on Mp-SnO2/TiO2NTs, 3.1 times higher than that on TiO2NTs. Compared with traditional SnO2/Ti electrodes, the Mp-SnO2/TiO2NTs displays smaller electrochemical impedance, a larger electrochemical surface absorption volume, and lower reaction activation energy. The integrated photoelectrocatalytic (PEC) oxidation of p-nitrophenol wastewater on Mp-SnO2/TiO2NTs is investigated. Because of the remarkable synergistic effect between PC and EC performances of Mp-SnO2/TiO2NTs, toxic intermediates are easily incinerated, resulting in relatively low accumulated concentrations. In 4 h, the p-nitrophenol and TOC removal reaches 98% and 91%, respectively, and the toxicity of the wastewater vanishes. The mechanism of synergistic PEC degradation of refractory pollutants is also proposed. This study provides a distinctive integrated photoelectric material and a promising technique for treatment of highly concentrated refractory wastewater effluent.