Surface modification of nanosheet oxide photocatalysts

A range of Aurivillius oxides of the form Bi2An−1BnO3n+3 were evaluated for photodegradation of methylene blue dye. Variants included 2-, 3-, and 4-layered materials with B = Ti, Nb, or Ta and A = alkaline earths, alkali and rare earths. All phases were tested as their parent oxides and after acid-exchange to form stacked protonated nanosheets. Several high-activity catalysts were identified and improvements in the photodegradation rates were achieved both by milling to increase surface area and separately by acid protonation followed by dehydration. Both processes yielded marked improvements in the photodegradation rates, some with more than 3 times improvement. The improvement is attributed to improved adsorption after the surface reconstruction that occurs with acid treatment and dehydration.