We present a one-step approach to polydopamine-modified graphene hydrogel, with dopamine serving as both reductant and surface functionalization agents. The synthetic method is based on the spontaneous polymerization of dopamine and the self-assembly of graphene nanosheets into porous hydrogel structures. Benefiting from the abundant functional groups of polydopamine and the high specific surface areas of graphene hydrogel with three-dimensional interconnected pores, the prepared material exhibits high adsorption capacities toward a wide spectrum of contaminants, including heavy metals, synthetic dyes, and aromatic pollutants. Importantly, the free-standing graphene hydrogel can be easily removed from water after adsorption process, and can be regenerated by altering the pH values of the solution for adsorbed heavy metals or using low-cost alcohols for synthetic dyes and aromatic molecules.

We report the development of a highly efficient photocatalytic system by immobilizing high-quality CdS quantum dots and dendritic Pt nanocrystals on thiol-functionalized graphene substrates. We have demonstrated that the use of QDs with compact sizes leads to a dramatically enhanced performance in comparison with their bulk counterparts. Our design allows for systematic examination of the impact of QD sizes and the loading, morphology, and surface coating of the Pt nanocrystal cocatalyst on the H2 evolution activity. It was found that the CdS-Pt binary system has a high photocatalytic efficiency of 1.37 mmol h(-1) for visible light driven H2 evolution, and there was a 30% improvement by introducing the thiolated reduced graphene oxide to form the three-component CdS-Pt-Gcys nanocomposites. The highest H2 evolution rate of 2.15 mmol h(-1) (λ ≥ 420 nm) with a QE of 50.7% was achieved by further photo-annealing of the CdS-Pt-Gcys nanocomposites prior to the photocatalytic reaction.

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