Solvent-adsorbate interactions have a great impact on catalytic processes in aqueous systems. Implicit solvent calculations are inexpensive but inaccurate toward hydrogen bonds, while a full... Show moreSolvent-adsorbate interactions have a great impact on catalytic processes in aqueous systems. Implicit solvent calculations are inexpensive but inaccurate toward hydrogen bonds, while a full incorporation of explicit solvation is computationally demanding. Micro-solvation attempts to break this dilemma by including only those solvent molecules directly interacting with the solute and any nearby interfaces, thereby providing a compromise between accuracy and computational expenses. Here, we show that micro-solvation of *OH and its relation to adsorption sites is largely transferable across late transition metal nanoparticles. Solvation energies for *OH on nanoparticles of Ir, Pd, and Pt range from -0.63 +/- 0.04 eV to -0.67 +/- 0.12 eV, while those on Au and Ag are -0.75 +/- 0.07 eV and -1.01 +/- 0.05 eV, respectively. These results enable the use of average solvation corrections for *OH on late transition metal nanostructures. Show less
Due to a general feedstock shift, the chemical industry is charged with the task of finding ways to transform renewable ketones into value-added products. A viable route to do so is the... Show moreDue to a general feedstock shift, the chemical industry is charged with the task of finding ways to transform renewable ketones into value-added products. A viable route to do so is the electrochemical hydrogenation of the carbonyl functional group. Here we report a study on acetone reduction at platinum single-crystal electrodes using online electrochemical mass spectroscopy, in situ Fourier transform infrared spectroscopy and density functional theory calculations. Acetone reduction at platinum displays a remarkable structural sensitivity: not only the activity, but also the product distribution depends on the surface crystallographic orientation. At Pt(111) neither adsorption nor hydrogenation occur. A decomposition reaction that deactivates the electrode happens at Pt(100). Acetone reduction proceeds at the (110) steps: Pt[(n – 1)(111) × (110)] electrodes produce 2-propanol and Pt[(n + 1)(100) × (110)] electrodes produce propane. Using density functional theory calculations, we built a selectivity map to explain the intricacies of the acetone reduction on platinum. Finally, we extend our conclusions to the reduction of higher aliphatic ketones. Show less
This work deals with the interconversions of various nitrogen-containing compounds on Pt(111) and Pt(100) electrodes in contact with acidic solutions of nitrate. Via its reduction, nitrate acts... Show moreThis work deals with the interconversions of various nitrogen-containing compounds on Pt(111) and Pt(100) electrodes in contact with acidic solutions of nitrate. Via its reduction, nitrate acts merely as the source of adsorbed nitrogen-containing intermediates, which then undergo complex oxidative or reductive transformations depending on the electrode potential. Nitrate reduction to ammonium is structure sensitive on Pt(111) and Pt(100) because it is mediated by *NO, the adsorption and reactivity of which is also structure sensitive. Accordingly, previous knowledge from *NO electrochemistry is useful to streamline nitrate reduction and elaborate a comprehensive picture of nitrogen-cycle electrocatalysis. Our overall conclusion for nitrate reduction is that the complete conversion to ammonium under prolonged electrolysis is possible only if the reduction of nitrate to nitric oxide, and the reduction of nitric oxide to ammonium are feasible at the applied potential. Among the two surfaces studied here, this condition is fulfilled by Pt(111) in a narrow potential region. (C) 2018 Elsevier Ltd. All rights reserved. Show less
The electrochemical oxidation of ammonia to dinitrogen is a model reaction for the electrocatalysis of the nitrogen cycle, as it can contribute to the understanding of the making/breaking of NN, NO... Show moreThe electrochemical oxidation of ammonia to dinitrogen is a model reaction for the electrocatalysis of the nitrogen cycle, as it can contribute to the understanding of the making/breaking of NN, NO, or NH bonds. Moreover, it can be used as the anode reaction in ammonia electrolyzers for H2 production or in ammonia fuel cells. We study here the reaction on the N2-forming Pt(1 0 0) electrode using a combination of electrochemical methods, product characterization and computational methods, and suggest a mechanism that is compatible with the experimental and theoretical findings. We propose that N2 is formed via an ∗NH + ∗NH coupling step, in accordance with the Gerischer-Mauerer mechanism. Other NN bond-forming steps are considered less likely based on either their unfavourable energetics or the low coverage of the necessary monomers. The NN coupling is inhibited by strongly adsorbed ∗N and ∗NO species, which are formed by further oxidation of ∗NH. Show less
