Nanocarbon-based Photocatalysts: rGO/Metal Oxides Composite Membranes

Abstract

It is widely accepted that graphene as well as reduced graphene oxide (rGO) have shown many superior properties such as electron mobility, excellent thermal and electrical conductivity, and large theoretical specific surface area. Previous research has shown significant enhancement of the photocatalytic property of semiconductors by compositing with rGO, which was largely attributed to the function of rGO or graphene as the electron sink. Moreover, the incorporation of graphene in photocatalytic systems also renders new format and new properties to photocatalysts. This MPhil project focuses on the synthesis of photocatalytic membranes formed by the embedment of Cu2O and/ or TiO2 nanowires in reduced graphene oxide, and their photocatalytic applications in water purification, such as destruction of organic dyes and persistent organic pollutants, as well as hydrogen production from ammonia solution. The literature review summarizes various types of graphene-based photocatalysts through different synthesis methods, and points out major factors that can influence photocatalytic efficiency. In the second part of the research, the research was aimed at fabricating a graphene based photocatalyst which can show superior photocatalytic efficiency under UV-Vis range. For this purpose, a heterojunction photocatalytic membrane consisting of Cu2O and TiO2 nanowires was produced. The resulting membrane benefitted from in- between reduced graphene oxide (rGO) sheets which was fabricated by applying a facile process from colloidal suspension. The designed membrane exhibits significantly enhanced activity under UV-Vis range, surpassing nanowires dispersions, owing to heterojunction formation and concurrent electron and hole transfer on rGO sheets. Furthermore, the membrane also possesses increased permeability and photocorrosion resistance. The described design and fabrication method of a rGO facilitated heterojunction photocatalytic membrane can be used in significant areas of applications including energy and environment developments. The focus of the final part of the research was to design a photocatalyst to produce hydrogen from ammonia solution. My study showed that the rGO/TiO2 NWs membrane results in 30-fold enhancement in photocatalytic H2 production compared with TiO2 NWs alone.