Effect of 3D titanium substrates with TiO2 nanotube arrays on photoelectrocatalysis degradation of phenol

Abstract

TiO2 nanotube array electrodes are coated on 3D titanium foam and mesh by the anodic oxidation procedure to investigate the effect of electrode substrates. Distribution homogeneity, crystal shape, structure, and light absorption of TiO2 nanotube are the same, orientations are different due to the planar structure of the titanium foam and the non-planar structure of the titanium mesh. However, the performance of the photoelectrocatalysis, phenol degradation, and charge transfer significantly influences by anode substrates. Although the photocurrent density of titanium mesh is 3.29 mA·cm−2, which is 1.5% lower than that of titanium foam, 96.1% ± 2% of the phenol can be degraded by the titanium mesh anode in 120 min with a degradation efficiency of 86.5% ± 3% after 4 cycles, demonstrated titanium mesh substrate is better than titanium foam. The mechanism results show that·OH and photoelectric synergy play a primary role in phenol degradation, and electrocatalysis (29.8%) increased by anode substrates, is better than photocatalysis (17.9%). The electric field enhances by electrocatalysis, resulting in accelerating electron transfer and decreasing in the recombination of electron and hole. Due to its porous structure and large specific surface area, the 3D substrate improves mass transport, providing more photocatalysts, reactants, and reaction sites for photoelectrochemical reactions, further enhancing photoelectric synergy, and ultimately promoting phenol degradation. This study confirms the role of 3D anode titanium substrate and encourages electric field enhancement to solve the recombination of electrons and holes.