Surface Modification and Work-Functional Engineering of Hematite Photoanodes via Layer-by-Layer Assembly for Solar Water Oxidation

Abstract

Artificial photosynthesis has drawn great attention for decades as a promising solution to 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 processes in a carbon-neutral manner. 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, hematite-based photoanode for solar water oxidation by layer-by-layer assembly of cationic graphene oxide (GO) nanosheets and anionic molecular metal oxides as a charge transporting/separation material and water oxidation catalyst, respectively. It was found that their sequential deposition significantly improves the photocatalytic performance and stability of the hematite photoanode by facilitating charge transport and transfer across the electrode/electrolyte interface. Unexpectedly, it was also found that deposition of alternating layers of cationic and anionic functional materials allow us to engineer work-function of hematite electrode beneficial for charge transport by forming an interfacial dipole layer. We believe that the present study can provide not only a general and simple method to fabricate an efficient photosynthetic device, but also an insight to scientists and engineers for designing of a novel electrochemical/photoelectrochemical device.