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Graphene oxide (GO) is a versatile 2D material whose properties can be tuned by changing the type and concentration of oxygen-containing functional groups attached to its surface. However, a detailed knowledge of the dependence of the chemo/physical features of this material on its chemical composition is largely unknown. We combine classical molecular dynamics and density functional theory simulations to predict the structural and electronic properties of GO at low degree of oxidation and suggest a revision of the Lerf-Klinowski model. We find that layer deformation is larger for samples containing high concentrations of epoxy groups and that correspondingly the band gap increases. Targeted chemical modification of the GO surface appears to be an effective route to tailor the electronic properties of the monolayer for given applications. Our simulations also show that the chemical shift of the C-1s XPS peak allows one to unambiguously characterize GO composition, resolving the peak attribution  uncertainty often encountered in experiments.

An understanding of the interaction of water with the anatase (101) surface is crucial for developing strategies to improve the efficiency of the photocatalytic reactions involved in solar water splitting. Despite a number of previous investigations, it is still not clear if water preferentially adsorbs in its molecular or dissociated form on anatase (101). With the aim of shedding some light on this controversial issue, we report the results of periodic screened-exchange density functional theory calculations of the dissociative, molecular and mixed adsorption modes on the anatase (101) surface at various coverages. Our calculations support the suggestion that surface adsorbed OH groups are present which has been made on the basis of recently measured X-ray photoelectron spectroscopy, temperature programmed desorption and scanning tunnelling microscopy data. It is also shown that the relative stability of water adsorption on anatase (101) can be understood in terms of a simple model based on the number and nature of the hydrogen bonds formed as well as the adsorbate-induced atomic displacements in the surface layers. These general conclusions are found to be insensitive to the specific choice of approximation for electronic exchange and correlation within density functional theory. The simple model of water-anatase interactions presented here may be of wider validity in determining the geometry of water-oxide interfaces.

A new approach for the study of photocatalytic heterojunctions based on a layer-by-layer PDOS has been developed. Our combination of experimental and theoretical calculations reveals the importance of interfacial effects when a heterojunction is formed that can dictate the performance of a heterojunction.