Noble-metal-free Co-N-graphene/PDI for significant enhancement of photocatalytic performance

Abstract

Single-atom based photocatalysts have been widely used in the degradation of organic pollutants due to their excellent activity, nearly 100 % atomic utilization efficiency and well-defined active centers. Here, we propose a single Co atom cocatalyst coordinated by nitrogen-doped graphene (Co-NG) to enhance the photocatalytic activity of perylene diimide (PDI) toward bisphenol A (BPA) degradation. Firstly, the self-assembled PDI on the surface of Co-NG exhibits a uniform dispersion state, which facilitates electron transport across the interface. Secondly, Nitrogen-doped graphene can act as a charge transfer bridge to facilitate charge migration from PDI to single Co atom catalytic center. Therefore, in the photocatalytic degradation of BPA, the Co-NG/PDI composite photocatalyst showed a significant increase in activity. 7 % Co-NG/PDI composite possesses the best photocatalytic performance, and the apparent rate is 6.64 times and 7.6 times higher than those of self-assembled PDI and Co-NG. The excellent activity is due to its high photogenerated carrier migration and transfer efficiency. Furthermore, the results of free radical capture experiment and ESR test confirm that singlet oxygen, superoxide radical, hydroxyl radical and hole are the main active species in the degradation process of BPA. We detected the intermediate products and proposed the degradation by LC-MS analysis. This study may provide a promising sunlight-driven photocatalyst for the treatment of the BPA in wastewater.