Self-assembling reduced graphene quantum dots on hematite photoanode for passivating surface states toward significantly improved water splitting

Hematite is a promising photoanode material but limited by its large overpotential (0.5-0.6 V) toward water splitting. The slow kinetics and high density of trapping states are the main factors. The former could be improved by catalyst modification for improved kinetics, while the latter is normally suppressed by passivating trapping states with atomic layer deposition-formed conformal overlayers. Up to date only a few of oxides and carbon materials were used to passivate hematite photoanode via wet chemical method, such as A1(2)O(3), TiO2 and reduced graphene oxide sheets. Herein, rGQDs as another carbon material are self-assembly onto hematite for the first time, which remarkably increases the photocurrent by 8.0 times at 1.23 V. The passivation of surface states confirmed by photoluminescence spectroscopy has significantly change in the radiative recombination, and can used well explain the great improvement. Importantly, this work clearly demonstrates a mass-productive and inexpensive solution-based self-assembly approach is also an efficient surface passivation technique. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.