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Electrochemical CO[Formula: see text] reduction is a potential route to the sustainable production of valuable fuels and chemicals. Here, we perform CO[Formula: see text] reduction experiments on Gold at neutral to acidic pH values to elucidate the long-standing controversy surrounding the rate-limiting step. We find the CO production rate to be invariant with pH on a Standard Hydrogen Electrode scale and conclude that it is limited by the CO[Formula: see text] adsorption step. We present a new multi-scale modeling scheme that integrates ab initio reaction kinetics with mass transport simulations, explicitly considering the charged electric double layer. The model reproduces the experimental CO polarization curve and reveals the rate-limiting step to be *COOH to *CO at low overpotentials, CO[Formula: see text] adsorption at intermediate ones, and CO[Formula: see text] mass transport at high overpotentials. Finally, we show the Tafel slope to arise from the electrostatic interaction between the dipole of *CO[Formula: see text] and the interfacial field. This work highlights the importance of surface charging for electrochemical kinetics and mass transport.

This study aims to improve our understanding of some differences in odd and even chain-length alkanethiol self-assembled monolayers (SAMs) using infrared reflection absorption spectroscopy (IRRAS) and density functional theory (DFT). Xe, Kr, CH2Cl2, CD2Cl2, and CDCl3 were used experimentally to perturb the CH2 and CH3 stretches arising from the tail region of the SAM films and changes in position and intensity were monitored in the infrared. Using DFT methods, noble gases and CH2Cl2 were added to models of the SAM monolayers, and energies and vibrational spectra were calculated. It was observed that perturbing species affected the CH3 symmetric and asymmetric stretches on hexadecanethiol SAMs (an "even" SAM with a 16-carbon backbone) while on pentadecanethiol SAMs (an "odd" SAM with a 15-carbon backbone) both CH2 and CH3 symmetric and asymmetric stretches were affected. Films formed with shorter chain-length species, hexanethiol (even) and pentanethiol (odd), had less consistent results, likely due to more disorder in the alkanethiol chains from weaker van der Waals interactions. Adsorption energies for different perturbing species on the monolayers were higher for the hexanethiol than the pentanethiol. The vibrational spectrum of pentanethiol monolayers with adsorbed species mainly showed shifts to higher frequencies for CH2 and CH3 stretches; for hexanethiol, shifts to lower frequencies for CH2 stretches and higher frequencies for CH3 stretches were observed. Thus, the odd and even alkanethiol SAMs were affected differently by the perturbing species as observed both experimentally and computationally. [ABSTRACT FROM AUTHOR]

We present an experimental and computational investigation into the rhodium-catalyzed ring-opening reactions of heterobicyclic alkenes with heteroarene nucleophiles. The reaction provides a facile route to trans-substituted dihydronaphthalen-1-ol and 1-amino-dihydronaphthalene products in up to a 95% yield as a single diastereomer. This reaction is 100% atom-economic and offers C–C bond formation without prior functionalization of the coupling partners. The mechanism and origins of selectivity were probed with density functional theory (DFT) at the MN15/Def2-TZVPP level of theory. The energetic barriers between iridium- and rhodium-catalyzed pathways were compared via DFT. Additionally, the reactivity and energetic barriers across diverse heterobicyclic alkenes and heteroarenes were calculated to unveil their relative reactivity. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of CO2 is known to be influenced by the identity of the alkali metal cation in the electrolyte; however, a satisfactory explanation for this phenomenon has not been developed. Here we present the results of experimental and theoretical studies aimed at elucidating the effects of electrolyte cation size on the intrinsic activity and selectivity of metal catalysts for the reduction of CO2. Experiments were conducted under conditions where the influence of electrolyte polarization is minimal in order to show that cation size affects the intrinsic rates of formation of certain reaction products, most notably for HCOO-, C2H4, and C2H5OH over Cu(100)- and Cu(111)-oriented thin films, and for CO and HCOO- over polycrystalline Ag and Sn. Interpretation of the findings for CO2 reduction was informed by studies of the reduction of glyoxal and CO, key intermediates along the reaction pathway to final products. Density functional theory calculations show that the alkali metal cations influence the distribution of products formed as a consequence of electrostatic interactions between solvated cations present at the outer Helmholtz plane and adsorbed species having large dipole moments. The observed trends in activity with cation size are attributed to an increase in the concentration of cations at the outer Helmholtz plane with increasing cation size.

The electrocatalyzed ammonia oxidation reaction (AOR) is a potential pathway toward waste ammonia remediation, energy generation, and the synthesis of value‐added products. To date, mechanistic studies have focused on elucidating the progress of AOR on Pt‐based catalysts with an established pathway for N2$\mathrm{N_2}$ only. In this work, density functional theory was applied to determine the lowest energy intermediates toward nitrogen gas, nitrite, and nitrate formation on β$\beta$‐Ni(OH)2$\mathrm{Ni(OH)_2}$, a promising electrocatalyst material for AOR. It was found that dinitrogen formation progresses via NH‐NH coupling, whereas nitrite and nitrate formation occurs via deprotonation of ammonia to form adsorbed N and subsequent hydroxylation to form oxygenated intermediates. This work is the first to report a mechanism for nitrite and nitrate formation and will also serve as a benchmark for future studies on Ni‐based materials. [ABSTRACT FROM AUTHOR]

The kinetics of the methanolysis of seven methyl aryl carbonates (3) and two methyl alkyl carbonates (4) promoted by [[12[ane]N3:Zn:(OC[H.sub.3])].sup.+] and [[[La.sub.2][(OC[H.sub.3]).sub.2]].sup.4+] catalysts (1 and 2, respectively) have been studied at 25.0°C. Brensted plots of the log [k.sup.obs.sub.2] values for methanolysis versus aryloxy and alkoxy leaving group (LG) [sup.s.sub.s]p[K.sup.HOAr.sub.a] or [sup.s.sub.s]p[K.sup.HOR.sub.a] values (the p[K.sub.a] values of the parent ArOH or ROH in methanol) for substrates 3 and 4 show an apparent downward break at [sup.s.sub.s]p[K.sub.a] ~16.6 and 15.2 with [[12[ane]N3:Zn:(OC[H.sub.3])].sup.+] and [[[La.sub.2][(OC[H.sub.3]).sub.2]].sup.4+], respectively. The breakpoint is not due to a change in rate-limiting step in a two-step process involving metal ion delivery of a coordinated methoxide to a transiently associated substrate and the subsequent breakdown of a tetrahedral intermediate to form product. The more satisfactory explanation is that the break arises when one correlates the rate constants for two dissimilar sets of substrates, namely aryloxy- and alkoxy-substituted 3 and 4. DFT calculations for the 1-promoted reactions of methyl 4-nitrophenyl carbonate (3b), which has a good aryloxy leaving group, and methyl isopropyl carbonate (4b), which has a relatively poor alkyl one, indicate that the catalyzed processes involve two steps. Accordingly, the methanolysis of all 3 having [sup.s.sub.s]p[K.sup.HOAr.sub.a] values for the parent phenols [less than or equal to] 15.3 involves rate-limiting nucleophilic attack and fast breakdown. For the isopropyl alkyl derivative (4b) having a [sup.s.sub.s]p[K.sup.HOR.sub.a] > 18.13, the rate- liming step is the metal ion promoted breakdown of a tetrahedral intermediate. The catalytic system employing 2 has utility for the catalytic decomposition of poly(bisphenol A carbonate). In a semi-optimized system where 1000 mg of poly(bisphenol A carbonate), treated at 100°C for 30 min in 2 mL of 60:40 chloroform-methanol containing La[(OTf).sub.3]:NaOMe (5:7.5 mmol [L.sup.-1]), the reaction gave an 84% yield of bisphenol A, corresponding to >300 turnovers per catalyst. Key words: methanolysis, catalysis, carbonate, polycarbonate, reaction mechanism, DFT computations. On etudie la cinetique de la methanolyse de sept carbonates de methylaryle (3) et de deux carbonates de methylalkyle (4) favorisee par les catalyseurs [[12[ane]N3:Zn:(OC[H.sub.3])].sup.+] et [[[La.sub.2][(OC[H.sub.3]).sub.2]].sup.4+] (1 et 2 respectivement) a 25,0°C. Les courbes de Bronsted des valeurs du log [k.sup.obs.sub.2] pour la methanolyse en fonction des valeurs du [sup.s.sub.s]p[K.sup.HOAr.sub.a] ou du [sup.s.sub.s]p[K.sup.HOR.sub.a] du groupe partant aryloxy ou alkoxy (les valeurs du p[K.sub.a] du ArOH ou du ROH parent dans le methanol) pour les substrats 3 et 4 revelent une apparente rupture a la baisse aux valeurs de ~16,6 et 15,2 du [sup.s.sub.s]p[K.sub.a] avec [[12[ane]N3:Zn:(OC[H.sub.3])].sup.+] et [[[La.sub.2][(OC[H.sub.3]).sub.2]].sup.4+], respectivement. Le point de rupture n'est pas attribuable a un changement de l'etape limitant la vitesse dans un processus en deux etapes faisant intervenir la fourniture de l'ion metallique d'un methoxyde coordonne a un substrat provisoirement associe et la decomposition subsequente d'un intermediaire tetraedrique pour former le produit. Une explication plus satisfaisante est que la rupture a lieu lorsqu'on etablit une correlation entre les constantes de vitesse de deux ensembles dissemblables de substrats, nommement les composes 3 et 4 contenant des substituants aryloxy et alkoxy. Des calculs par la methode de la theorie de la fonctionnelle de la densite (DFT) pour les reactions favorisees par 1 du carbonate de methyl-4 nitrophenyle (3b), qui possede un bon groupe partant aryloxy, et du carbonate de methyl-isopropyle (4b), dont le groupe partant est relativement mauvais, indiquent que les processus catalyses comprennent deux etapes. Par consequent, la methanolyse de tous les derives 3 dont les valeurs du [sup.s.sub.s]p[K.sup.HOAr.sub.a] pour les phenols parents sont ≤ 15,3 comporte une attaque nucleophile limitant la vitesse et une decomposition rapide. Pour le derive isopropyl alkyle (4b) dont le [sup.s.sub.s]p[K.sup.HOR.sub.a] > 18,13, l'etape limitant la vitesse est la decomposition de l'intermediaire tetraedrique favorisee par l'ion metallique. Le systeme de catalyse faisant intervenir 2 utilise la decomposition catalytique du poly(carbonate de bisphenol A). Dans un systeme semi-optimise ou 1000 mg de poly(carbonate de bisphenol A), traites a 100°C pendant 30 min dans 2 mL d'un melange 60:40 de chloroforme-methanol contenant La[(OTf).sub.3]: NaOMe (5:7,5 mmol [L.sup.-1]), la reaction a donne du bisphenol A avec un rendement de 84%, ce qui correspond a > 300 moles de produit par mole de catalyseur. [Traduit par la Redaction] Mots-cles: methanolyse, catalyse, carbonate, polycarbonate, mecanisme de reaction, calculs DFT., Introduction Polycarbonate (PC), such as that made from bisphenol A and phosgene, is widely used in glazing, eyewear, packaging containers, electronics, and optical media (DVD, Blu-ray) and is notable for [...]

Improving the activity and selectivity of heterogeneous metal electrocatalysts has been the primary focus of CO2 electroreduction studies, however, the stability of these materials crucial for practical application remains less understood. In our work, the impact of the reaction intermediates (RIs) on the energetics and mechanism of metal-atom migration is studied with a combination of density functional theory (DFT) and ab initio molecular dynamics (AIMD) on pure transition metals Cu, Ag, Au, Pd, as well as three Cu4−xPdx (x = 1,2, and 3) alloys. Reaction intermediates (RIs) for the CO2 reduction reaction, H2 evolution, and O2 reduction were considered. The effect of adsorbed RIs was observed to facilitate metal atom migration generally by decreasing the kinetic barriers for migration. The atomic mobility trends in the commonly used CO2RR metal electrocatalysts in the course of electrolysis conditions were established. This study provides theoretical insight into understanding how the electrocatalyst may undergo promoted restructuring in the presence of RIs under realistic electrochemical conditions. [ABSTRACT FROM AUTHOR]

The electrochemical ammonia oxidation reaction (AOR) has applications in hydrogen storage and ammonia waste remediation. Using density functional theory, we investigate the mechanism of AOR on Ir, Rh, and their alloys at varied atomic ratios (Ir75Rh25$\text{Ir}_{75}\text{Rh}_{25}$, Ir50Rh50$\text{Ir}_{50}\text{Rh}_{50}$, and Ir25Rh75$\text{Ir}_{25}\text{Rh}_{75}$) toward N2$\text{N}_2$(g), NO2−$\text{NO}_2^-$(aq), and NO3−$\text{NO}_3^-$(aq) formation. This work introduces a method for computational alloy design by considering both electronic energy and configurational entropy. The structures considered are selective to N2$\text{N}_2$(g) formation and all favored *N–N coupling. An Ir50Rh50$\text{Ir}_{50}\text{Rh}_{50}$ alloy was found to reduce the theoretical onset potential for N2$\text{N}_2$(g) formation relative to pure Ir while not exhibiting a downhill coupling step corresponding to catalyst poisoning by *N as shown for pure Rh, consistent with previous experimental work. The formation of NO2−$\text{NO}_2^-$(aq) and NO3−$\text{NO}_3^-$(aq) demand significantly higher potentials, typically limited by the final hydroxylation step before desorption. [ABSTRACT FROM AUTHOR]