Catalysis under Cover: Enhanced Reactivity at the Interface between (Doped) Graphene and Anatase TiO₂

Abstract

The "catalysis under cover" involves chemical processes which take place in the confined zone between a 2D material, such as graphene, h-BN, or MoS2, and the surface of an underlying support, such as a metal or a semiconducting oxide. The hybrid interface between graphene and anatase TiO2 is extremely important for photocatalytic and catalytic applications because of the excellent and complementary properties of the two materials. We investigate and discuss the reactivity of O2 and H2O on top and at the interface of this hybrid system by means of a wide set of dispersion-corrected hybrid density functional calculations. Both pure and boron- or nitrogen-doped graphene are interfaced with the most stable (101) anatase surface of TiO2 in order to improve the chemical activity of the C-layer. Especially in the case of boron, an enhanced reactivity toward O2 dissociation is observed as a result of both the contribution of the dopant and of the confinement effect in the bidimensional area between the two surfaces. Extremely stable dissociation products are observed where the boron atom bridges the two systems by forming very stable B-O covalent bonds. Interestingly, the B defect in graphene could also act as the transfer channel of oxygen atoms from the top side across the C atomic layer into the G/TiO2 interface. On the contrary, the same conditions are not found to favor water dissociation, proving that the "catalysis under cover" is not a general effect, but rather highly depends on the interfacing material properties, on the presence of defects and impurities and on the specific reaction involved.

Ordered Single-Crystalline Anatase TiO2Nanorod Clusters Planted on Graphene for Fast Charge Transfer in Photoelectrochemical Solar Cells

“…This qualitative observation is in agreement with the result of the photoluminescence spectra in Figure d. [8c] Based on above systematic investigations, fast charge transport of rGO/ATRCs for photovoltage performance was undoubtedly ascertained.…”

“…The abundance of oxygen‐containing functional groups (Figure S1, Supporting Information) makes GO an appropriate substrate for the heteroepitaxial growth of TiO 2 . [8a,11b] As shown in Figure a–c, at the early reaction stage (10 h), the TiO 2 nanorods planted sparsely on the surface of rGO, and some of well‐marked wrinkles on rGO remained uncovered, as indicated by the arrow in Figure b. Upon prolonging the reaction time to 14 h, the TiO 2 nanorods grew sideways on the rGO substrate, turning from slightly scattered to densely dotted, as showed in Figure d–f.…”

Confined catalysis under two-dimensional materials

“…Many experiments provide solid evidence that 2D spaces under the 2D material overlayers can act as stable nanoreactors for molecule adsorption and chemical reactions, which provide intriguing confined spaces for catalysis (22,25,(28)(29)(30)(31). A few sophisticated theoretical studies have been conducted to understand reactions under graphene covers in a quantitative way (32,33). Overall, a 2D microenvironment formed under 2D material can provide an ideal and practical model system to explore the fundamentals of confined catalysis.…”

Computational electrochemistry of doped graphene as electrocatalytic material in fuel cells

“…The nature, structure, and electronic properties of the interface can strongly influence the adsorption/dissociation energies as well as the desorption barriers of small gaseous molecules. The dissociation energy of O 2 is highly enhanced (see Figure ) when the reaction takes place at the interface between BG and a semiconducting oxide, such as (101) anatase as well as at the interface with an easily oxidizable metal, such as Cu (111) …”