Development of metal-supported catalysts for graphene production from spent tea grounds

Abstract

Graphene, a single-atom-thick 2-dimensional sheet of carbon atoms densely arranged in a hexagonal lattice, has captured much attention from scientists and engineers due to its unique mechanical and electrical properties. Synthesis of graphene by catalytic chemical vapor deposition (CVD) using gaseous hydrocarbons has been widely investigated. However, researchers are still seeking for precursors which are sustainable and accessible to obtain a high quality of graphene. This work delivers a comprehensive study on catalyst development for graphene fabrication from the spent tea ground. Various kinds of catalysts were developed for pyrolysis of spent tea grounds to produce methane, which is the carbon source for graphene fabrication. The catalysts were characterized by analytical techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) to evaluate the metal/metal oxide crystallinity, metal oxidation states, morphology, and crystallinity nature, correspondingly. Moreover, the effect of the reaction temperature, catalyst dosage, catalyst calcination temperature and types of spent tea grounds on the methane generation were studied. With the optimized metal catalyst and pyrolysis reaction, the whole catalytic system was practically applied in the graphene synthesis. The commercial spent tea grounds were used as the sole carbon source for growing graphene monolayer on copper foil by catalytic CVD. This method utilizes the optimized monometallic and bimetallic catalysts to efficiently catalyse the pyrolytic reaction of the spent tea ground and the generated fragments subsequently are deposited on the copper foil substrate. Raman spectroscopy confirmed that the graphene was successfully deposited on the copper foil substrate using either specifically designed Ru/alumina, or bimetallic CoRu-based catalysts. This new approach not only demonstrates a new route of transforming the spent tea grounds into useful graphene material, but also promotes a concept of “waste-to-functional materials” to achieve the goal of “carbon-zero” by Year 2050.

Date of Award	2022
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Xijun HU (Supervisor)