Chemical recycling of the waste anodic electrolyte from the TiO2 nanotube preparation process to synthesize facet-controlled TiO2 single crystals as an efficient photocatalyst

Abstract

Anodization has been reported to be an effective electrochemical method to prepare vertically ordered, upright oriented TiO₂ nanotubes for efficient photocatalysis, solar cells and many other fields. However, this process generates a large amount of residual anodic electrolytes that are rich in toxic fluorides, which are usually discarded and cause environmental contamination. Here, we propose a facile and effective method to prepare both pristine and N-doped TiO₂ nanocrystals based on the recycling of waste ethylene glycol electrolyte from the widely-used anodic process. Under identical conditions, both the pristine and N-doped TiO₂ nanocrystals exhibited nearly twice as high photocatalytic activity in decomposition of humic acids and bentazone than Degussa P25, one of the best commercial TiO₂ photocatalysts. The preparation method had obvious economic and environmental benefits. The prepared TiO₂ nanocrystals possessed superior photocatalytic degradation capacities for refractory pollutants, and could be used for efficient water treatment.