Nemanja Gavrilov

Carbonised polyaniline and polypyrrole: towards advanced nitrogen-containing carbon materials

Polyaniline (PANI) and polypyrrole (PPY) undergo carbonisation in an inert/reduction atmosphere and vacuum, yielding different nitrogen-containing carbon materials. This contribution reviews various procedures for the carbonisation of PANI and PPY precursors, and the characteristics of obtained carbonised PANI (C-PANI) and carbonised PPY (C-PPY). Special attention is paid to the role of synthetic procedures in tailoring the formation of C-PANI and C-PPY nanostructures and nanocomposites. The review considers the importance of scanning and transmission electron microscopies, XPS, FTIR, Raman, NMR, and EPR spectroscopies, electrical conductivity and adsorption/desorption measurements, XRD, and elemental analyses in the characterisation of C-PANIs and C-PPYs. The application of C-PANI and C-PPY in various fields of modern technology is also reviewed.

Hydrogen Adsorption on Palladium and Platinum Overlayers: DFT Study

Hydrogen adsorption on twenty different palladium and platinum overlayer surfaces with (111) crystallographic orientation was studied by means of periodic DFT calculations on the GGA-PBE level. Palladium and platinum overlayers here denote either the Pd and Pt mono- and bilayers deposited over (111) crystallographic plane of Pd, Pt, Cu, and Au monocrystals or the (111) crystallographic plane of Pd and Pt monocrystals with inserted one-atom-thick surface underlayer of Pd, Pt, Cu, and Au. The attention was focused on the bond lengths, hydrogen adsorption energetics, mobility of adsorbed hydrogen, and surface reactivity toward hydrogen electrode reactions. Both the ligand and strain effects were considered, found to lead to a significant modification of the electronic structure of Pd and Pt overlayers, described through the position of the d-band center, and tuning of the hydrogen adsorption energy in the range that covers approximately 120 kJmol−1. Mobility of hydrogen adsorbed on studied overlayers was found to be determined by hydrogen-metal binding energy. Obtained results regarding Pd layers on Pt(111) and Au(111) surfaces, in conjunction with some of the recent experimental data, were used to explain its electrocatalytic activity towards hydrogen evolution reaction.

DFT study of interaction of O, O2, and OH with unreconstructed Pt(hkl) (h, k, l = 0, 1) surfaces—similarities, differences, and universalities

Adsorption of O, O2, and OH on Pt(111), Pt(100), and Pt(110) surfaces was studied using periodic DFT calculations. It was found that generally adsorbate-surface interaction strengths increase with the decrease in surface packing density. On the Pt(111) surface the dissociation of O2 molecule was not predicted, but it was predicted on Pt(100) and Pt(110) surfaces. While the strength of the adsorbate-substrate interaction decreases with the rise in surface coverage by O atoms, in the case of OH adsorption adsorbate layer gets stabilized at higher surface coverage through the hydrogen bonding. In spite of all the mentioned differences, single parameter of surface electronic structure was identified, being useful for the explanation of the adsorption trends at different adsorption sites for O and OH adsorption on Pt surfaces of various crystallographic orientations and also provided a deeper understanding of atomic oxygen adsorption as a function of surface coverage.

Adsorption of Acetonitrile on Platinum and its Effects on Oxygen Reduction Reaction in Acidic Aqueous Solutions—Combined Theoretical and Experimental Study

AbstractCombined theoretical and experimental study of acetonitrile (AcN) adsorption on platinum was performed and its effects on the kinetics of oxygen reduction reaction in HClO4 and H2SO4 solutions were examined. Using periodic density functional theory calculations, it was shown that AcN molecule can interact with Pt surface either through the unsaturated π electron system or via lone electron pair of nitrogen atom. In both cases, adsorption energy decreases upon increasing coverage, while the modification of electronic structure of Pt surface is localized to the adsorption site. By combining the results of the DFT calculations with the results of blank cyclic voltammetry and rotating disk electrode voltammetry in O2-saturated solutions, it was concluded that the effects of AcN on Pt surface chemistry and ORR kinetics are primarily steric in nature. Resulting measured ORR activities of polycrystalline platinum in the presence of AcN are due to the combination of (i) suppression of (bi)sulfate adsorption (in H2SO4 solution), (ii) suppression of surface oxidation (in both H2SO4 an HClO4 solution), and (iii) site blockage by adsorbed AcN (or products of its electrochemical transformations). Graphical Abstractᅟ