Construction of Three-Dimensional Hemin-Functionalized Graphene Hydrogel with High Mechanical Stability and Adsorption Capacity for Enhancing Photodegradation of Methylene Blue

A three-dimensional hemin-functionalized graphene hydrogel (Hem/GH) was prepared by a facile self-assembly approach. The as-prepared Hem/GH showed good mechanical strength with a storage modulus of 609-642 kPa and a high adsorption capacity to organic dye contaminants (341 mg g-1 for rhodamine B). Moreover, Hem/GH could be used as a photosensitizer for the photocatalytic degradation of organic dyes and displayed superior photodegradation activity of methylene blue (MB). This result was better than that of counterparts such as graphene hydrogel (GH) and commercial catalyst P25. The excellent cycling performance of the Hem/GH was well maintained even after multiple cycles on adsorption process and photocatalytic reaction. Interestingly, after the photodegradation of MB, a light-induced pH change of the solution from alkaline pH 8.99 to acidic pH 3.82 was observed, and 10 wt % total organic carbon remained. The liquid chromatography/time-of-flight mass spectrometry (LC/TOF-MS) analysis confirmed the generation of acidic degradation products. The photocatalytic mechanism was further investigated by trapping experiments, which revealed that the MB degradation was driven mainly by the participation of O2•- radicals in the photocatalytic reaction. As an extended application, visually intuitive observation showed the as-prepared Hem/GH also had strong antibacterial properties. These results suggest that Hem/GH could be potentially used for practical application due to its high adsorption ability, excellent photocatalytic activity, and strong antibacterial properties.