Epitaxial graphene boosts photocatalysis in titania nanoparticles

The choice of an interfacial layer of epitaxial graphene to support titania nanoparticles has been revealed as a key ingredient to dramatically increase their capability to split water and produce hydrogen. 

D. De Angelis et al., Carbon 157, 350 (2020)
The long-standing seek for efficient, sustainable and naturally-abundant materials for catalysis has recently targeted carbonaceous material as an ideal candidate for several technologically-relevant applications, of which the hydrogen production is the most captivating. In particular, graphene, owing to its unique electronic and transport properties, is a very good candidate to improve the efficiency of photo-absorbers in photocatalysis and photo-electrocatalysis. Since the first titania-graphene nanocomposites have been developed, large efforts have been devoted to employ graphene in photocatalytic materials, since it reduces the electron-hole (e-h) recombination rate, it allows the modification of the band alignment, it reduce overpotentials and the titanium oxide the band gap, thus allowing electrons to be excited into the conduction band by visible light. While most of these graphene-titania hybrids have been obtained by employing graphene oxide or reduced graphene oxide, which are characterized by poorer transport properties than high-quality epitaxial Gr. Moreover, the presence of structural defects and functional groups in GO and RGO, are known to be centers of e-h recombination, thus lowering the photocatalysis efficiency. 
In this paper, we discuss the growth, the structural/electronic characterization and the photocatalytic activity trends of a nano-architecture designed with the aim to investigate the role of the substrate below graphene on the electronic band structure and alignment of the supported photoabsorbers. By using epitaxial graphene grown on Ir(111) as a prototype of quasi free-standing system, we have prepared a novel interface consisting of TiO2 nanoparticles supported by a layered structure based on high-quality epitaxial monolayer graphene, two-dimensional titanium-oxide and metal. 


Our study has proven that the photocatalytic activity of these architectures in the production of hydrogen via the hydrogen evolution reaction is spectacularly enhanced if a 2D TiO1.5 layer is intercalated between graphene and the metallic substrate. We attribute this enhancement to the different doping level induced in graphene by the TiO1.5 layer and by the shifts of the Ti d band of the titania nanoparticles.

The change in the electronic structure of the layered material is indicative of a reduced probability of recombination of electrons and holes that are produced in the photoexcitation process. Our results are a proof that the use of 2D materials, and in particular of transfer-free epitaxially grown materials and their heterostructures, could be applied for the design of novel energy related materials with greatly improved functionalities.

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Interfacial two-dimensional oxide enhances photocatalytic activity of graphene/titania via electronic structure modification
Dario De Angelis, Francesco Presel, Naila Jabeen, Luca Bignardi, Daniel Lizzit, Paolo Lacovig, Silvano Lizzit, Tiziano Montini, Paolo Fornasiero, Dario Alfè, and Alessandro Baraldi
Carbon 157, 350 (2020)

Last Updated on Sunday, 09 October 2022 16:19