Agradecimentos: The authors acknowledge the financial support from the Brazilian agency FAPESP (Grants 2015/23775-3 and 2014/11736-0), Capes and CNPq. F. L. S and A. F. N gratefully acknowledge support from FAPESP (Grant 2017/11986-5) and Shell and the strategic importance of the support given by ANP (Brazil’s National Oil, Natural Gas and Biofuels Agency) through the R&D levy regulation. We also thank Dr. Frank. E. Osterloh from University of California - UC Davis (USA), for providing access to surface photovoltage spectrometer and Dr. Renato Vitalino Gonçalves from USP-São Carlos for the XPS measurements Ver menos

Abstract: In this work, the role of the single layer graphene as overlayer on hematite photoanodes surface was investigated for water oxidation reaction via photoelectrochemical process. Single layer graphene (SLG) was synthesized by chemical vapour deposition (CVD) and transferred from the copper foil to the a-Fe2O3 photoanode surface. To ensure the purity and quality of SLG, elemental composition of the samples was investigated in all steps and no metal (Cu) trace was found after the transference onto the photoanode surface. The photocurrent density of a-Fe2O3/graphene photoanode was increased from 1.25 to 1.64?mA?cm-2 at 1.23 VRHE in comparison to bare a-Fe2O3 photoanode. The role of SLG added on a-Fe2O3 and the charge carrier dynamics were investigated combining transient absorption spectroscopy (TAS) and surface photovoltage spectroscopy (SPS). These combined techniques revealed that the photogenerated holes had their lifetime increased as a function of applied bias and after the SLG deposition onto the a-Fe2O3 photoanode surface. As consequence, the photochemical separation and transfer of the photogenerated charge carriers became more efficient in the presence of SLG. The incorporation of SLG on a-Fe2O3 photoanode is believed to suppress the surface traps, enabling holes to diffuse into the solid-liquid interface and promoting water oxidation reaction driven by sunlight irradiation Ver menos