Controlled crystal facet of tungsten trioxide photoanode to improve on-demand hydrogen peroxide production for in-situ tetracycline degradation.

Advanced oxidation processes utilizing hydrogen peroxide (HO) are widely employed for the treatment of organic pollutions. However, the conventional anthraquinone method for HO synthesis is unsuitable for this application owing to its hazardous and costly nature. Alternative approaches involve a photoelectrochemical method. Herein, tungsten trioxide (WO) photoanode has been used for the conversion of HO into HO through oxidation reaction from a PEC system, simultaneously utilizing in-situ generated hydroxyl (OH) radicals for tetracycline degradation. By manipulating the ratio of crystal facets between (020) and (200) of the WO photoanode, a significant improvement in HO production has been achieved by increasing the proportion of (020) facet. The production rate of WO photoanode enriched with the (020) facet is approximately 1.9 times higher than that enriched with (200) facet. This enhanced HO production performance can be attributed to the improved formation of OH radicals and the accelerated desorption of HO on the (020) facet. Simultaneously, the in-situ generated OH radicals are applied for tetracycline degradation. Under illumination of sunlight stimulator for 180 min, the optimal photoanode achieves a degradation rate of 86.7% for tetracycline. Furthermore, the resulting chemicals have been analyzed, revealing that CHO and CHO were formed as the primary products. Notably, these products exhibit significantly lower toxicity compared to tetracycline. This study presents a promising approach for the rational design of WO based photoanodes for oxidation reaction, including not only HO production but also the efficient degradation of organic pollutants.