Phenylamine-Functionalized rGO/TiO<sub>2</sub> Photocatalysts: Spatially Separated Adsorption Sites and Tunable Photocatalytic Selectivity

Abstract

The preferential adsorption of targeted contaminants on a photocatalyst surface is highly required to realize its photocatalytic selective decomposition in a complex system. To realize the tunable preferential adsorption, altering the surface charge or polarity property of photocatalysts has widely been reported. However, it is quite difficult for a modified photocatalyst to realize the simultaneously preferential adsorption for both cationic and anionic dyes. In this study, to realize the selective adsorption for both cationic and anionic dyes on a photocatalyst surface, the negative reduced graphene oxide (rGO) nanosheets and positive phenylamine (PhNH<sub>2</sub>) molecules are successfully loaded on the TiO<sub>2</sub> surface (PhNH<sub>2</sub>/rGO-TiO<sub>2</sub>) with spatially separated adsorption sites, where the negative rGO and positive PhNH<sub>2</sub> molecules work as the preferential adsorption sites for cationic and anionic dyes, respectively. It was interesting to find that although all the TiO<sub>2</sub> samples (including the naked TiO<sub>2</sub>, PhNH<sub>2</sub>/TiO<sub>2</sub>, rGO-TiO<sub>2</sub>, and PhNH<sub>2</sub>/rGO-TiO<sub>2</sub>) clearly showed a better adsorption performance for cationic dyes than anionic dyes, only the PhNH<sub>2</sub>/rGO-TiO<sub>2</sub> with spatially separated adsorption-active sites exhibited an opposite photocatalytic selectivity, namely, the naked TiO<sub>2</sub>, PhNH<sub>2</sub>/TiO<sub>2</sub>, and rGO-TiO<sub>2</sub> showed a preferential decomposition for cationic dyes, while the resultant PhNH<sub>2</sub>/rGO-TiO<sub>2</sub> exhibited an excellently selective decomposition for anionic dyes. In addition, the resultant PhNH<sub>2</sub>/rGO-TiO<sub>2</sub> photocatalyst not only realizes the tunable photocatalytic selectivity but also can completely and sequentially decompose the opposite cationic and anionic dyes

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