A DFT and SERS study of synergistic roles of thermodynamics and kinetics during the electrocatalytic reduction of benzyl chloride at silver cathodes

Tailoring Ag Electron Donating Ability for Organohalide Reduction: A Bilayer Electrode Design

“…Using the above-mentioned criteria, we have been able to predict a stable support electrode (i.e., Ti) that can enhance the adsorption behavior of the Ag electrode. It is important to note here that in practice the catalytic activity of electrodes for organohalide reduction depends on a number of factors such as the strength of adsorption, the surface coverage, and the rate of desorption of reactant, intermediate, product, and solvent molecules as well as a range of other factors. ,,, As a result, enhancement of the dissociative adsorption behavior of the Ag electrode cannot solely be a sufficient condition for achieving better catalytic activity, but undoubtedly, it is an important and necessary criterion. We proposed Ti as one viable candidate to isolate the work function effect.…”

“…All of these previous studies also indicate that the synergy between the thermodynamic effect and the kinetic (mechanistic) effect dictates the catalytic activity of a material. The effect of the electrode surface on the catalytic activity is linked through the molecular and dissociative chemical adsorption of the reactants, intermediates, and products, respectively. ,,− The sensitivity of electrocatalysis on the surface adsorption has been confirmed via the volcano-shaped dependence of the catalytic activity for different materials obtained when plotted against the metal and relevant atomic (involving in creating the rate-determining critical bond) interaction. , For example, in the case of halothane reduction, Langmaier and Samec obtained the volcano plot of the measured half-wave potential ( E 1/2 ) of the reduction with respect to the Br–metal bond strength . Here we derived the half-wave potential, following Langmaier and Samec, to be an explicit function of the equilibrium organic halide standard reduction potential, E 0 , the charge transfer rate, k 0 , and the surface adsorption coefficient, β (more derivation details can be found in the Supporting Information): E 1 / 2 = E 0 + R T α F ln true( n F A k 0 m true) + R T α F ln true( 2 β 1 − α 2 + β c 0 true) where n is number of electrons ( n = 1 for the first rate-limiting electron transfer reaction), m is the mass transfer number, c 0 is the bulk concentration of organic halide, α is the charge transfer coefficient (which was reported as α = 0.38, 0.73, 0.45, 0.19, and 0.32 for Ag, Au, Cu, Ti, and Hg, respectively, from measuring the halothane reduction on various rotating-disc electrodes in 1 M NaOH in methanol or water), and T is temperature.…”

“…The reductive dehalogenation of carbon–halogen bonds plays a critical role in the catalytic abetment of environmental pollutants, organic synthesis, fundamental studies of electron transfer chemistry, and other fields. − Reductive dehalogenation approaches, for example, are quite promising for the removal of toxic and very harmful chemicals such as polychloro­biphenyls (PCBs), chlorinated aliphatic hydrocarbons (CAHs), volatile organic compounds (VOCs), chloro­nitrobenzenes (CNBs), etc. This has prompted tremendous recent interest in the electrochemical reduction of organohalides which involves the cleavage of carbon–halogen bonds under electrochemical conditions. ,− Current can be used as a green redox reagent or electron as a green reductant, thus providing sustainable and clean avenues for organic electrosynthesis, ,, pollution remediation, , etc. Electrochemical routes also help to avoid the use of hazardous reagents and the potential risk of secondary pollution. ,, The practical realization of direct, selective, and energy efficient electrochemical dehalogenation of organohalides (by defeating the competing processes such as hydrogen evolution reaction or HER) over inert electrodes is difficult and will likely require the use of catalytic surfaces. , …”

“…Although limited, there are few experimental and theoretical studies that can be highlighted that attempt to deconvolute the multistep complex organohalide reduction processes. ,, Previous studies on the dissociative electron transfer (DET) mechanism of electrochemical reduction of organic halides have shown the overall process to be a two-electron reduction process where the first electron transfer step was found to be the rate-limiting step (RDS). , The first step involving the carbon–halogen bond dissociation can be either stepwise or concerted in nature. ,,, The radical and halide ions are produced at the end of this step irrespective of the intermediate pathway. All of these previous studies also indicate that the synergy between the thermodynamic effect and the kinetic (mechanistic) effect dictates the catalytic activity of a material.…”

Electrochemical Surface-Enhanced Raman Spectroscopy for Aniline Adsorbed on Silver Electrodes: A DFT Study of the Anharmonic Effects of Amino Wagging Vibrational Modes

“…In this work, we will use a molecule-metal cluster model − combined with DFT calculations and further consider the anharmonic effect to analyze the normal Raman and SERS spectra of aniline molecules based on harmonic approximation. The anharmonic approximation here includes two aspects, the anharmonic effect of the potential energy surface and the polarizability.…”