Constructing Stake Structured TiO₂-NTs/Sb-Doped SnO₂ Electrode Simultaneously with High Electrocatalytic and Photocatalytic Performance for Complete Mineralization of Refractory Aromatic Acid

This Article puts forward a new idea to construct an electrode combining the advantages of a TiO 2 nanotube photocatalyst and an excellent Sb-doped SnO 2 electrocatalyst, which realized high electrocatalytic (EC) and photocatalytic (PC) oxidation efficiency at the same time. Under vacuum conditions, in virtue of the titanium oxide nanotubes (TiO 2 -NTs) as a template, well dispersed Sb-doped SnO 2 (particle size 20 nm) was embedded into TiO 2 -NTs (diameter 60−90 nm and wall thickness 10−20 nm), resulting in the stake structured TiO 2 -NTs/Sb-doped SnO 2 electrode (TiO 2 -NTs/SnO 2 ). The loading amount of Sb-doped SnO 2 on a TiO 2 -NTs/SnO 2 electrode is 21.4 g m −2, which is increased by 2 times compared with the situation of direct loading Sb-doped SnO 2 on the Ti substrate (Ti/SnO 2 ). The crystal lattice parameter of SnO 2 becomes smaller, and crystal lattice parameter of TiO 2 is larger, so the combination between TiO 2 -NTs and Sb-doped SnO 2 becomes more tight. Compared with the electrochemical properties of Ti/SnO 2, the apparent rate constant of benzoic acid (BA) conversion ( k s ) on the TiO 2 -NTs/SnO 2 electrode is (1.44 ± 0.04) × 10 −4 s −1 and that of Ti/SnO 2 is (1.01 ± 0.03) × 10 −4 s −1 . Furthermore, its electrochemical stability and antideactivation properties are greatly improved, and the accelerated service lifetime of the TiO 2 -NTs/SnO 2 electrode is increased by 1.0 time. The initial instantaneous current efficiency of the degradation of BA on the TiO 2 -NTs/SnO 2 electrode is 26.8%, and that on the Ti/SnO 2 electrode is 13.3%. Compared with the PC properties of TiO 2 -NTs, the band gap of TiO 2 -NTs/SnO 2 decreases from 3.22 to 2.93 eV, and the photoconversion efficiency is raised to 26.1% from 8.2%. k s on TiO 2 -NTs/SnO 2 is (0.82 ± 0.02) × 10 −4 s −1, and that of TiO 2 -NTs is (0.41 ± 0.02) × 10 −4 s −1 . In the photoelectrocatalytic (PEC) aspect of BA, the current densities under 3.0 V increase by 4.0, 2.1, and 0.09 mA cm −2 on the TiO 2 -NTs/SnO 2, Ti/SnO 2, and TiO 2 -NTs electrodes, respectively. The initial instantaneous current efficiency of the TiO 2 -NTs/SnO 2 electrode increases to 100%, which is much higher than 41.7% and 31.3% on Ti/SnO 2 and TiO 2 -NTs electrodes, respectively. k s on TiO 2 -NTs/SnO 2 is (5.26 ± 0.16) × 10 −4 s −1, which is 3.2 times that of Ti/SnO 2 and 4.8 times that of TiO 2 -NTs. The TiO 2 -NTs/SnO 2 electrode has both excellent PC properties and excellent EC properties. After PEC degradation of BA on the electrode for 3.5 h, chemical oxygen demand (COD) removal is 100%. This research has enriched the PEC theory on the electrode’s microstructured interface and developed a new idea for exploring highly efficient PEC technology.