Enhancing Hematite Photoanode Activity for Water Oxidation by Incorporation of Reduced Graphene Oxide

Abstract

Two effective methods to prepare reduced graphene oxide (rGO)/hematite nanostructured photoanodes and their photoelectrochemical characterization towards water splitting reactions are presented. First, graphene oxide (GO) is reduced to rGO using hydrazine in a basic solution containing tetrabutylammonium hydroxide (TBAOH), and then deposited over the nanostructured hematite photoanodes previously treated at 750 °C for 30 min. The second method follows the deposition of a paste containing a mixture of hematite nanoparticles and rGO sheets by the doctor-blade method, varying the rGO concentration. Since hematite suffers from low electron mobility, a low absorption coefficient, high recombination rates and slow reaction kinetics, the incorporation of rGO in the hematite can overcome such limitations due to graphene's exceptional properties. Using the first method, the rGO incorporation results in a photocurrent density increase from 0.56 to 0.82 mA cm(-2) at 1.23 VRHE. Our results indicate that the rGO incorporation in the hematite photoanodes shows a positive effect in the reduction of the electron-hole recombination rate.

Challenges and prospects about the graphene role in the design of photoelectrodes for sunlight-driven water splitting

“…The two-dimensional rGO nanosheets present high electron mobility and π-electron conjugation. 78 Besides the light absorbance improvements, owing to its excellent electronic properties, the presence of rGO on top of the photoanodes can lead to an increase of the charge separation efficiency. As a consequence, a lower bulk recombination is obtained, which makes rGO as an effective electron capturing and transferring material.…”

Efficient Nanoporous Hematite Photoanodes Prepared by Electron Beam Evaporation and Au Modification

“…One approach relies on using porous hematite films in different structural designs including nano‐sheets, nano‐flakes, nanowires, nanorods, and an extremely thin absorber layer of hematite deposited onto a scaffold in order to shorten light propagation distance in thick hematite layers . For these structures, addition of doping materials and surface modification with different co‐catalysts have been demonstrated to improve cell performance. An alternative approach to improve the PEC performance of hematite benefits from light management strategies based on resonant light trapping or plasmonic,, to improve optical absorption in extremely thin hematite layers.…”

Understanding the Role of Reduced Graphene Oxide in the Electrolyte of Dye-Sensitized Solar Cells

“…RGO is less conducting than pristine graphene due to residual oxygen-containing functional groups such as carbonyl, hydroxyl, or epoxy, which still persist in its structure. The electron-accepting ability presented by RGO sheets is still an outstanding property that can be used to enhance electron transport properties when RGO is incorporated in inorganic matrices to form nanocomposites. − Our group has reported interesting results combining RGO sheets with TiO 2 nanoparticles and their applications in methylene blue dye photodegradation, photocatalysis for water splitting, CO 2 photorreduction, and as electron transport layer in organic solar cells (OPV). , …”