Interfacial engineering of hematite photoanodes through layer-by-layer assembly for solar water splitting

Abstract

Solar to chemical conversion is considered as a promising solution to energy and environmental problems because various chemicals (e.g., hydrogen, formate, and syngas) can be produced from wasted carbon dioxide and abundant water in a carbon-neutral manner. It can be enabled by a series of photoelectrochemical processes with various functional materials, which include semiconducting materials for exciton generation, conducting materials for exciton dissociation and charge transport, and redox catalysts for target-chemical reactions. For the development of efficient and stable solar to chemical energy conversion devices, it is imperative to precisely assembly these components. Here, we report that an efficient and stable photoanode for solar water oxidation can be readily fabricated by layer-by-layer (LbL) assembly. In particular, cationic graphene oxide (GO) nanosheets and anionic molecular metal oxide catalysts were readily deposited on hematite without alteration of their properties using the LbL method. It was found that their sequential deposition significantly improves the photocatalytic performance and stability of hematite for solar water oxidation. In addition, the deposition of multilayers of cationic and anionic polymer electrolyte prior to the GO and catalyst layers improve the photoanode performance even further by allowing the engineering of the flat band potential of the underlying hematite photoanode. We believe that the present study opens a new avenue for an efficient photosynthetic device, as well as an academic insight to scientists and engineers for designing novel electrochemical/photoelectrochemical devices.