Covalent Functionalization of GaP(110) Surfaces via a Staudinger-Type Reaction with Perfluorophenyl Azide

Ugeda, Miguel M.; Bradley, Aaron J.; Rodrigo, Lucía; Yu, Min; Liu, Wenjun; Doak, Peter; Riss, Alexander; Neaton, Jeffrey B.; Tilley, T. Don; Pérez, Rúben; Crommie, Michael F.

doi:10.1021/acs.jpcc.6b10691

Cited by 3 publications

(1 citation statement)

References 24 publications

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“…Another reason, on the basis of results and discussions in our work, is that these types of sites have some partial positive charge leading to an ESP well which electrostatically polarizes and stabilizes the HOMO. On the basis of our calculations, the class of closed-shell molecules discussed here always bind preferably to the most electropositive surface constituent even when the difference of electronegativity is small − (examples are given in section 21 of the Supporting Information).…”

Section: Resultsmentioning

confidence: 96%

Nature of Lone-Pair–Surface Bonds and Their Scaling Relations

et al. 2018

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We investigate the (surface) bonding of a class of industrially and biologically important molecules in which the chemically active orbital is a 2 p electron lone pair located on an N or O atom bound via single bonds to H or alkyl groups. This class includes water, ammonia, alcohols, ethers, and amines. Using extensive density functional theory (DFT) calculations, we discover scaling relations (correlations) among molecular binding energies of different members of this class: the bonding energetics of a single member can be used as a descriptor for other members. We investigate the bonding mechanism for a representative (HO) and find the most important physical surface properties that dictate the strength and nature of the bonding through a combination of covalent and noncovalent electrostatic effects. We describe the importance of surface intrinsic electrostatic, geometric, and mechanical properties in determining the extent of the lone-pair-surface interactions. We study systems including ionic materials in which the surface positive and negative centers create strong local surface electric fields, which polarize the dangling lone pair and lead to a strong "electrostatically driven bond". We emphasize the importance of noncovalent electrostatic effects and discuss why a fully covalent picture, common in the current first-principles literature on surface bonding of these molecules, is not adequate to correctly describe the bonding mechanism and energy trends. By pointing out a completely different mechanism (charge transfer) as the major factor for binding N- and O-containing unsaturated (radical) adsorbates, we explain why their binding energies can be tuned independently from those of the aforementioned species, having potential implications in scaling-driven catalyst discovery.

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Section: Resultsmentioning

confidence: 96%

Nature of Lone-Pair–Surface Bonds and Their Scaling Relations

et al. 2018

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Cobalt Porphyrin–Polypyridyl Surface Coatings for Photoelectrosynthetic Hydrogen Production

et al. 2017

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Hybrid materials that link light capture and conversion technologies with the ability to drive reductive chemical transformations are attractive as components in photoelectrosynthetic cells. We show that thin-film polypyridine surface coatings provide a molecular interface to assemble cobalt porphyrin catalysts for hydrogen evolution onto a visible-light-absorbing p-type gallium phosphide semiconductor. Spectroscopic techniques, including grazing angle attenuated total reflection Fourier transform infrared spectroscopy, confirm that the cobalt centers of the porphyrin macrocycles coordinate to pyridyl nitrogen sites of the organic surface coating. The cobalt porphyrin surface concentration and fraction of pyridyl sites coordinated to a cobalt center are quantified using complementary methods of ellipsometry, inductively coupled plasma mass spectrometry, and X-ray photoelectron spectroscopy. In aqueous solutions under simulated solar illumination the modified cathode is photochemically active for hydrogen production, generating the product gas with near-unity Faradaic efficiency at a rate of ≈10 μL min cm when studied in a three-electrode configuration and polarized at the equilibrium potential of the H/H couple. This equates to a photoelectrochemical hydrogen evolution reaction activity of 17.6 H molecules s Co, the highest value reported to date for a molecular-modified semiconductor. Key features of the functionalized photocathode include (1) the relative ease of synthetic preparation made possible by application of an organic surface coating that provides molecular recognition sites for immobilizing the cobalt porphyrin complexes at the semiconductor surface and (2) the use of visible light to drive cathodic fuel-forming reactions in aqueous solutions with no added organic acids or sacrificial chemical reductants.

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