Layer-by-Layer Assembly of Graphene Oxide Nanosheets and Molecular Metal Oxides on Hematite for Solar Water Splitting

Abstract

Solar to chemical conversion, the so-called artificial photosynthesis has drawn great attention for decades as a promising solution to modern energy and environmental problems. For example, we can produce valuable chemicals (e.g., formate, synthesis gas, and methanol) from abundant carbon dioxide and water through a series of photoelectrochemical process. For the successful development of efficient and stable photosynthetic devices, it is imperative to precisely assemble various functional materials such as semiconducting materials for exciton generation, conducting materials for exciton dissociation and charge transport, and redox catalysts for target-chemical reactions. Here, we report the development of an efficient and stable photoanode for solar water oxidation by layer-by-layer assembly of cationic graphene oxide (GO) nanosheets and anionic molecular metal oxides. GO and molecular metal oxides were used as a charge-transporting layer and water oxidation catalyst, respectively, and readily deposited on hematite without alteration of their properties, according to electron microscopy and spectroscopic analysis. It was found that their sequential deposition significantly improves the photocatalytic performance and stability of hematite. The present study demonstrate the validity of layer-by-layer assembly techniques for the fabrication of electrochemical/photoelectrochemical devices and can provide a new insight for the design of novel devices.