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Graphene is thought to be a promising materials for many applications. However, pristine graphene is not suitable for most electrochemical devices, where defect engineering is crucial for its performance. We demonstrate how boron doping of graphene can alter its reactivity, electrical conductivity and potential application for sodium and aluminium storage, with the emphasis on novel metal-ion batteries. Using DFT calculations, we investigate both the influence of boron concentration and the oxidation of the material, on the mentioned properties. It is demonstrated that the presence of boron in graphene increases its reactivity towards atomic hydrogen and oxygen-containing species, in other words, it makes B-doped graphene more prone to oxidation. Additionally, the presence of these surface functional groups significantly alters the type and strength of the interaction of Na and Al with the given materials. Boron-doping and oxidation of graphene is found to increase Na storage capacity of graphene by the factor of up to 4., Comment: 22 pages, 2 of which are supplementary information. 10 figures, 2 tables

Pristine graphene interacts relatively weakly with Al, which is a specie of importance for novel generations of metal-ion batteries. We employ DFT calculations to explore the possibility of enhancing Al interaction with graphene. We investigate non-doped and N-doped graphene nanoribbons, address the impact of the edge sites, which are always present to some extent in real samples, and N-containing defects on the material's reactivity towards Al. The results are compared to that of pristine graphene. We show that introduction of edges does not affect the energetics of Al adsorption significantly by itself. On the other hand, N-doping of graphene nanoribbons is found to affect the adsorption energy of Al to the extent that strongly depends on the type of N-containing defect. While graphitic and pyrrolic N induce minimal changes, the introduction of edge NO group and doping with in plane pyridinic N result in Al adsorption nearly twice as strong as on pristine graphene. The obtained results could guide the further design of advanced materials for Al-ion rechargeable batteries., Comment: 20 pages in total, 2 of which are supplementary information

The development of new electrochromic materials and devices, like smart windows, has an enormous impact on the energy efficiency of modern society. One of the crucial materials in this technology is nickel-oxide. Ni-deficient NiO shows anodic electrochromism whose mechanism is still under debate. Using DFT+U calculations, we show that Ni vacancy generation results in the formation of hole polarons localised at the two oxygens next to the vacancy. Upon Li insertion or injection of an extra electron into Ni-deficient NiO, one hole gets filled, and the hole bipolaron is converted into a hole polaron well-localized at one O atom. Furthermore, the calculated absorption coefficients demonstrate that Li insertion/extraction or rather the addition/removal of an extra electron into Ni-deficient NiO can lead to switching between the oxidized (colored) and the reduced (bleached) states. Hence, our results suggest a new mechanism of Ni-deficient NiO electrochromism not related to the Ni2+/Ni3+ transition but based on the formation and annihilation of hole polarons in oxygen p-states., Comment: main text (19 pages, 6 figures, 1 table, 44 references) and supplementary information (4 pages, 4 figures)

Electrocatalytic properties of materials are governed by the electronic structure, stability, and reactivity of the surface layer which is exposed to the electrolyte. Over the years, different strategies have been developed to tailor electrocatalyst surfaces but also to reduce the cost of these materials, which is the bottleneck for any practical application. When a very thin metallic layer, intended to serve as an electrocatalyst, is placed over a substrate, its configuration is influenced by the structure of the substrate due to lattice mismatch, while the electronic structure is affected due to the strain and the electronic effects of the support. This results in altered bonding within the electrocatalyst layer and the modification of its electronic properties when compared to the pure phase. In this contribution, we address the possibilities of theoretical prediction of surface properties of atomically thin electrocatalyst films formed over different substrates, focusing on the metal side of the electrified interface. While all these properties can be calculated quite easily using modern computational techniques (but used with care), most often based on density functional theory, we also address an attractive, fast screening possibility to estimate the properties of monometallic and multimetallic overlayers using small sets of calculations on model systems. We discuss how lattice mismatch between a substrate and an overlayer can be used to predict the properties of electrocatalytic films, limitations of such approach, and a possibility of deploying of large databases which enable rapid prescreening of different support/overlayer systems for various electrocatalytic applications.

Due to its unique physical and chemical properties, graphene is being considered as a promising material for energy conversion and storage applications. Introduction of functional groups and dopants on/in graphene is a useful strategy for tuning its properties. In order to fully exploit its potential, atomic-level understanding of its interaction with species of importance for such applications is required. We present a DFT study of the interaction of sodium atoms with epoxy-graphene and analyze how this interaction is affected upon doping with boron and nitrogen. We demonstrate how the dopants, combined with oxygen-containing groups alter the reactivity of graphene towards Na. Dopants act as attractors of epoxy groups, enhancing the sodium adsorption on doped oxygen-functionalized graphene when compared to the case of non-doped epoxy-graphene. Furthermore, by considering thermodynamics of the Na interaction with doped epoxy-graphene it has been concluded that such materials are good candidates for Na storage applications. Therefore, we suggest that controlled oxidation of doped carbon materials could lead to the development of advanced anode materials for rechargeable Na-ion batteries., Comment: 16 pages, 6 figures

Molybdenum supported thin films of ScN, MgO and NaF with a Cu adatom have been studied in the framework of density functional theory. We have observed a charge transfer from the metal/film interface to the Cu atom and investigated its relation to surface and interface deformations. We find that a weak interaction between the metal and the film is a promising prerequisite for adatom charging. The detailed study of Cu/NaF/Mo and NaF/Mo indicates that the distortion of the NaF film caused by the Cu adsorption has essentially anharmonic character, as it is coupled to a strong charge redistribution in the system.

The present density functional theory study addresses the question whether the presence of H2O influences the catalytic activity of small gold clusters, Au1-4/MgO(100), towards the oxidation of carbon monoxide. To this end, we studied the (co-)adsorption of H2O and CO/O2 on these gold clusters. The ground state structures in the presence of all three molecular species, that we found, are Au1O2/MgO and Au2-4CO/MgO with H2O adsorbed on the surface in the proximity of the clusters-molecule complex. In this configuration the catalytic activity of Au1-4/MgO is indifferent to the presence of H2O. We also found that a stable, highly activated hydroperoxyl-hydroxyl complex, O2H\dot\dot OH, can be formed on Au1,3/MgO. For the catalytic active system Au8/MgO, it has been predicted that this complex opens an alternative catalytic reaction pathway towards CO oxidation. Our results suggest that this water mediated catalytic cycle is unlikely to occur on Au1,3/MgO. In the case of Au1/MgO the cycle is interrupted by the dissociation of the remaining (OH)2 complex after forming the first CO2 molecule. On Au3 /MgO the O2 H\dot\dot OH complex is likely to decompose upon the impact of a CO molecule, since three of its bond dissociation energies are comparable to the reaction barrier of the CO to CO2 oxidation.