Cu is in the spotlight as it represents the only metal capable of catalyzing CO2 reduction to multicarbon products. However, its catalytic performance is determined collectively by a number of parameters including its composition and structure, electrolyte, and cell configuration. It remains a challenge to disentangle and understand the individual effect of these parameters. In this work, we study the effect of the electrode–electrolyte interface on CO2 reduction in water by coating CuO electrodes with polymers of varying hydrophilicities/phobicities. Hydrophilic polymers such as poly­(vinyl alcohol) and poly­(vinylpyrrolidone) exert negligible influence, while hydrophobic polymers such as poly­(vinylidene fluoride) and polyethylene significantly enhance the activity, selectivity, and stability of CuO-derived electrodes toward C2H4 production. From ex situ characterizations, electrolysis in deuterated water, and molecular dynamics simulations, we propose that the improved catalytic performance triggered by hydrophobic polymers originates from restricted water diffusion and a higher local pH near the electrode surface. These observations shed light on interfacial manipulation for promoted CO2-to-C2H4 conversion.

Usually, electrografting of aryldiazonium salts results in the formation of covalently attached films <10 nm thick. In this work, we report on an electrografting procedure by which thick conducting films, even in the micrometer size range, can be formed on glassy carbon, gold, or stainless steel in a controlled manner. It is a prerequisite that the aryldiazonium salt contains a redox active moiety such as nitrobenzene, anthraquinone, or benzophenone to maintain charge propagation in the growing layer. In addition, electrografting proceeds only efficiently by way of using potential sweeping rather than electrolysis at a fixed potential. Sweeping is essential to continuously desorbing any physisorbed species that otherwise would clog the channels in the film and make it insulating. Cyclic voltammetry, polarization modulation infrared reflection absorption spectroscopy, ellipsometry, and profilometry are used to characterize the surfaces and, through this, explain the growth mechanism. Elucidation of the role of the substrate, solvent, and supporting electrolyte is included in the investigation.

Phenylethanethiolate monolayer-protected Au38 and Au140 nanoclusters were modified by ligand place exchange with a series of thiolated peptides. The peptides were homooligomers based on the alpha-aminoisobutyiric acid unit. The effects of changing the peptide concentration and the peptide length in the capping monolayer were studied by differential pulse voltammetry. The results showed that the redox behavior of the nanoparticles can be affected very significantly by such modifications. For example, the first oxidation peak of Au38, a cluster displaying molecule-like behavior, could be shifted positively by as much as 0.7-0.8 V. Detectable redox shifts were noted even when one single oriented peptide was in the Au140 monolayer. These effects were attributed to the molecular dipole moments of the peptide ligands.

Considerable interest in calcite crystallization has prompted many studies on organic molecule adsorption. However, each study has explored only a few compounds, using different methods and conditions, so it is difficult to combine the results into a general model that describes the fundamental mechanisms. Our goal was to develop a comprehensive adsorption model from the behavior of a range of organic compounds by exploring how common functional groups interact with calcite and the effects of various side groups and hydrogen on adsorption. We used density functional theory, with semiempirical dispersion corrections (DFT-D2), to determine adsorption energy on calcite {10.4} for nonpolar (benzene, ethane, and carbon dioxide) and oxygen containing polar molecules (water, methanol, ethanol, phenol, formic acid, acetic acid, propanoic acid, benzoic acid, formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, dimethyl ether, acetone, and furan). From the adsorption energies, within the transition state theory approximation, we derived desorption temperature for each molecule. Then we used X-ray photoelectron spectroscopy (XPS) to determine the desorption temperature for four representative molecules and compared the experimental results with those predicted. Carboxylic acids (R-COOH) adsorb more strongly than water and alcohols (R−OH), which in turn adsorb more strongly than the aldehydes (R-CHO). Attachment of a hydrogen atom or a side group changes adsorption behavior for hydroxyl and aldehyde functional groups but does not affect the carboxyl functional group significantly.