Computational screening of transition metal/p-block hybrid electrocatalysts for CO reduction.

Among all the pollutants in the atmosphere, CO has the highest impact on global warming, and with the rising levels of this pollutant, studies on developing various technologies to convert CO into carbon-neutral fuels and chemicals have become more valuable. In this work, we present a detailed computational study of electrochemical reduction of CO reaction (the CO RR) to methane and/or methanol over different transition metal-p block catalysts using density functional theory calculations. In addition to the catalyst structure, we studied reaction mechanisms using free energy diagrams that explain the product selectivity with respect to the competing hydrogen evolution reaction.

Size, Composition, and Support-Doping Effects on Oxygen Reduction Activity of Platinum-Alloy and on Non-platinum Metal-Decorated-Graphene Nanocatalysts.

Recent investigations reported in the open literature concerning the functionalization of graphene as a support material for transition metal nanoparticle catalysts have examined isolated systems for their potential Oxygen Reduction Reaction (ORR) activity. In this work we present results which characterize the ability to use functionalized graphene (via dopants B, N) to upshift and downshift the adsorption energy of mono-atomic oxygen, O* (the ORR activity descriptor on ORR Volcano Plots), for various compositions of 4-atom, 7-atom, and 19-atom sub-nanometer binary alloy/intermetallic transition metal nanoparticle catalysts on graphene (TMNP-MDG). Our results show several important and interesting features: (1) that the combination of geometric and electronic effects makes development of simple linear mixing rules for size/composition difficult; (2) that the transition from 4- to 7- to 19-atom TMNP on MDG has pronounced effects on ORR activity for all compositions; (3) that the use of B and N as dopants to modulate the graphene-TMNP electronic structure interaction can cause shifts in the oxygen adsorption energy of 0.

Similarities and differences for atomic and diatomic molecule adsorption on the B-5 type sites of the HCP(101̅6) surfaces of Co, Os, and Ru from DFT calculations.

The differences in relative adsorption energies for mono-atomic and diatomic prototype species (C,N,O,S,H,CO,NO,SO,CH,NH,H,O) relevant to catalytic processes such as Fischer-Tropsch and Ammonia Synthesis chemistry are investigated on the previously un-studied surface(s) of Co, Os, and Ru. Recent work in the literature has confirmed that catalytically relevant nanoparticles of HCP elements such as Co, Os, and Ru typically possess highly active 'B5' sites; unfortunately many early and extant theory and model-ing treatments of "stepped HCP surfaces" use created steps via manual deletion of atoms from an ideal HCP(0001) slab model. To date the differences in adsorption energies at various B5 step edge types, and any possible trends across the same type of B5 sites on various HCP catalyst species has not been thoroughly characterized.

Elucidation of Pathways for NO Electroreduction on Pt(111) from First Principles.

The mechanism of nitric oxide electroreduction on Pt(111) is investigated using a combination of first principles calculations and electrokinetic rate theories. Barriers for chemical cleavage of N-O bonds on Pt(111) are found to be inaccessibly high at room temperature, implying that explicit electrochemical steps, along with the aqueous environment, play important roles in the experimentally observed formation of ammonia. Use of explicit water models, and associated determination of potential-dependent barriers based on Bulter-Volmer kinetics, demonstrate that ammonia is produced through a series of water-assisted protonation and bond dissociation steps at modest voltages (<0.

Chiral "pinwheel" heterojunctions self-assembled from C60 and pentacene.

We demonstrate the self-assembly of C60 and pentacene (Pn) molecules into acceptor-donor heterostructures which are well-ordered and--despite the high degree of symmetry of the constituent molecules--chiral. Pn was deposited on Cu(111) to monolayer coverage, producing the random-tiling (R) phase as previously described. Atop R-phase Pn, postdeposited C60 molecules cause rearrangement of the Pn molecules into domains based on chiral supramolecular "pinwheels".

Rational Development of Ternary Alloy Electrocatalysts.

Improving the efficiency of electrocatalytic reduction of oxygen represents one of the main challenges for the development of renewable energy technologies. Here, we report the systematic evaluation of Pt-ternary alloys (Pt3(MN)1 with M, N = Fe, Co, or Ni) as electrocatalysts for the oxygen reduction reaction (ORR). We first studied the ternary systems on extended surfaces of polycrystalline thin films to establish the trend of electrocatalytic activities and then applied this knowledge to synthesize ternary alloy nanocatalysts by a solvothermal approach.

Trends in methanol decomposition on transition metal alloy clusters from scaling and Brønsted-Evans-Polanyi relationships.

A combination of first principles Density Functional Theory calculations and thermochemical scaling relationships are employed to estimate the thermochemistry and kinetics of methanol decomposition on unsupported subnanometer metal clusters. The approach uses binding energies of various atomic and molecular species, determined on the pure metal clusters, to develop scaling relationships that are then further used to estimate the methanol decomposition thermodynamics for a series of pure and bimetallic clusters with four atoms per cluster. Additionally, activation energy barriers are estimated from Brønsted-Evans-Polanyi plots relating transition and final state energies on these clusters.

Structures of dense glycine and alanine adlayers on chiral Cu(3,1,17) surfaces.

Density Functional Theory calculations have been used to predict the structures of dense glycine and alanine adlayers on Cu(3,1,17)(S). Facets of this chiral Cu surface result from adsorbate-induced surface reconstruction when glycine or alanine are adsorbed and annealed on Cu(100). We have calculated the surface energy changes associated with this surface reconstruction.

Structures of glycine, enantiopure alanine, and racemic alanine adlayers on Cu(110) and Cu(100) surfaces.

We have determined the structures of dense adlayers of glycine and alanine on the Cu(110) and Cu(100) surfaces using plane wave density functional theory. These calculations resolve several experimental controversies regarding these structures. Glycine exists on Cu(110) as a single adlayer structure, while on Cu(100) two distinct glycine adlayers coexist.

First-principles studies of chiral step reconstructions of Cu(100) by adsorbed glycine and alanine.

Adsorption of amino acids on Cu(100) is known experimentally to induce surface reconstructions featuring intrinsically chiral Cu(3,1,17) facets, but no information about the geometry of the molecules on these chiral facets is available. We present density-functional theory calculations for the structure of glycine and alanine at moderate coverages on Cu(3,1,17). As might be expected, molecules prefer to bind at the step edges on this surface rather than on the surface's (100)-oriented terraces.