With the rapid development of industry, bismuthbased semiconductors have been widely used for the photocatalytic degradation of organic contaminants discharged into wastewater. Herein, a Bi 2 O 3 /BiOCl (BBOC) heterojunction was constructed with high photocatalytic activity toward Rhodamine B (RhB) in the first cycle of the photocatalysis test, while the photocatalytic performance was drastically reduced after repeated testing. The adsorbed RhB molecules occupying the facial active sites of BBOC contributed to the decline of photocatalytic activity. The spent BBOC can be reactivated by the decomposition of the adsorbed RhB and the introduction of oxygen vacancies during calcination under an air atmosphere. The BBOC thus recovered exhibited a superior apparent rate constant of 0.08087 min −1 compared with 0.05228 min −1 of pristine BBOC. This study provided an effective strategy to investigate the deactivation/activation mechanism of bismuth-based heterojunction photocatalysts.

Photocatalytic water splitting is a convenient method to produce hydrogen as a renewable energy resource. GaZnNO solid solution with a controllable band gap of 2.3−2.8 eV is considered a promising photocatalyst, while the specific reaction mechanism is still not clear. In this research, the mechanism of photocatalytic water splitting by RuO 2 -modified GaZnNO solid solution was investigated. X-ray diffraction and scanning electron microscopy detection were used to verify the crystal form of the prepared photocatalysts. Brunauer−Emmett−Teller test was used to analyze the surface properties, and UV−vis diffuse reflection and photoluminescence spectra were used to investigate the abilities of light. Importantly, the hydroxyl radicals and photocatalytically generated oxygen were quantitively measured under different conditions. In conclusion, H 2 O 2 molecules were speculated to be the intermediates and • OH radicals were generated as the byproducts during the water oxidization reaction with GaZnNO solid solution photocatalysts. Ru deposition enhanced the photocatalytic activity by promoting the decomposition of hydrogen peroxide to oxygen. The photocatalytic organic decomposition of the catalysts was also investigated, and it is believed that the organics were mainly oxidized by photogenerated holes. The effect of Ru deposition on the mechanism of photocatalytic water splitting by GaZnNO solid solution was proposed in the end.

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