Novel visible-light-sensitized Chl-Mg/P25 catalysts for photocatalytic degradation of rhodamine B

- Chlorophyll and free-Mg loading increased visible light photoactivity of P25.
- Electrons donated from chlorophyll to P25 nanoparticles improved photoactivity.
- Free-Mg and chlorophyll complex structures result in a positive synergistic effect.
- Remaining free-Mg in the Mg2+ form inhibited the charge recombination.
- Complex structure between free-Mg and chlorophyll enhanced reusability of catalyst.

Photocatalytic reaction is known as one of the most promising processes to reduce global warming and environmental problems as well as offer sustainable energy sources. As nano-bio hybrid materials are potential alternatives for improving the efficiency of photocatalytic reactions, a unique chlorophyll and Mg co-modified P25 (Degussa P25, which consists of mixed phases between anatase and rutile) catalyst was synthesized and used as a visible light reactive photocatalyst in this research. The activity of obtained catalysts was evaluated from photocatalytic degradation of rhodamine B (RhB) under visible light, and the effect of chlorophyll source, co-modified chlorophyll and magnesium, and their loading amounts on photodegradation of RhB were investigated. It was found that the loading of extracted chlorophyll gave higher activity than that of Spirulina due to its greater possibility for direct contact between chlorophyll and P25, leading to more efficient electron transfer from chlorophyll to P25. In addition, loading free Mg together with chlorophyll led to the formation of a new complex structure, resulting in synergistic effect between chlorophyll-Mg and P25, and therefore an increase in photocatalytic performance and good reusability of catalysts. Proper amounts of chlorophyll and Mg loading on P25 (0.5Chl-0.1Mg/P25) could promote the photocatalytic activities such that they are approximately 2.3, 1.3 and 2.1 times those of P25, 0.5Chl/P25 and 0.1Mg/P25, respectively.

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