One-pot hydrothermal synthesis of Co(OH)2 nanoflakes on graphene sheets and their fast catalytic oxidation of phenol in liquid phase.

A cobalt hydroxide (Co(OH)2) nanoflake-reduced graphene oxide (rGO) hybrid was synthesized by a one-pot hydrothermal method using glucose as a reducing agent for graphene oxide (GO) reduction. The structural and surface properties of the material were investigated by scanning and transmission electron microscopies, energy-dispersive X-ray spectrometry, powder X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Catalytic activities of GO, rGO, Co(OH)2 and Co(OH)2-rGO in aqueous phenol degradation using peroxymonosulfate as an oxidant were compared. A synergetic effect on the catalytic activity was found on the Co(OH)2-rGO hybrid. Although rGO has weak catalytic activity, Co(OH)2-rGO hybrid showed a higher catalytic activity than Co(OH)2. The phenol degradation on Co(OH)2-rGO was extremely fast and took around 10 min for 100% phenol removal. The degradation was found to follow the first order kinetics and a mechanism for phenol degradation was presented.