SCHEDULED MAINTENANCE
Integrating reduced graphene oxide with microwave-subcritical water for cellulose depolymerization†
Abstract
Catalyst design and surface chemistry have long been regarded as the major foundations for the catalytic activity of carbon-based catalysts. However, surface modification of carbon-based catalysts typically involves huge quantities of strong acids that eventually leach into the solution contaminating the target compounds. We have previously demonstrated that the mixture of reduced graphene oxide (rGO) and residual cellulose would generate additional glucose after the first cycle by simply elevating the temperature. In this study, we sought to understand how rGO under microwave (MW)-subcritical water (subH2O) facilitates the depolymerization of cellulose. It was found out that the MW sensitizing properties of rGO improved, enhancing the electronic transport properties. The partial removal of functional groups has resulted into much smaller particles and formation of nanopores and nanovoids which facilitated the precise cleaving of the glycosidic bonds with glucose yields reaching up to 66 ± 4 wt% in as short as 5 min. The yield highly correlates with the H3O+/OH− concentration and hugely depends on the rGO structure that varies according to the synthesis method, preferably in the absence of water. The depolymerization mechanism takes place via random scission. This study indicates that rGO, in spite of having fewer functionalities than pristine graphene oxide (GO), can still be used for catalysis even without surface modification in combination with MW and subH2O.
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