No abstract

Due to their distinctive electronic, optical, and chemical properties, metal nanoplates represent important building blocks for creating functional superstructures. Here, a general deposition method for synthesizing Ag nanoplate architectures, which is compatible with a wide substrate range (flexible, curved, or recessed; consisting of carbon, silicon, metals, oxides, or polymers) is reported. By adjusting the reaction conditions, nucleation can be triggered in the bulk solution, on seeds and by electrodeposition, allowing the production of nanoplate suspensions as well as direct surface modification with open‐porous nanoplate films. The latter are fully percolated, possess a large, easily accessible surface, a defined nanostructure with {111} basal planes, and expose defect‐rich, particularly reactive edges in high density, making them compelling platforms for heterogeneous catalysis, and electro‐ and flow chemistry. This potential is showcased by exploring the catalytic performance of the nanoplates in the reduction of carbon dioxide, 4‐nitrophenol, and hydrogen peroxide, devising two types of microreactors, and by tuning the nanoplate functionality with derivatization reactions.

A facile synthetic route to form nanoporous (np) metallic materials is the (electro)­chemical dissolution of less noble metals from an alloy referred to as dealloying. In this study, we investigated the dynamic formation of np copper (np-Cu) films prepared from Zn–Cu alloys. The obtained np-Cu films were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, grazing-incidence X-ray diffraction, and X-ray photoelectron spectroscopy depth profiles. We show a clear correlation between the dealloying conditions [reaction time and electrolyte solution (0.1 M HCl (pH 1) and 1.3 M NaOH (pH 14))] and structural parameters (ligament size and chemical composition) for the np-Cu films. The dealloying process in 0.1 M HCl results in the formation of uniform ligaments in the np-Cu. However, the ligament size grows with decreasing Zn content, signifying a strong relation between Zn content and the ligament size. In contrast, dealloying in NaOH leads to ligament structures which are independent of the Zn content. This observation is likely based on the reduced surface mobility of the Cu (hydr)­oxide species and the completive reaction like redeposition of soluble Cu­(I) species to form Cu­(I) oxide crystals. This knowledge enables the development of synthetic guidelines for the preparation of tunable ligament size and content of less noble metal, which is highly critical for systematic studies.

A direct current in an electrochemical cell with a diluted liquid electrolyte leads to the displacement of ions within the solvent, while diffusion works against the resulting concentration differences. This study aims to experimentally evaluate a physicochemical ion transport model (source code provided) that describes current-driven concentration gradients in diluted electrolytes. Hereto, an aqueous 0.1 M CuSO 4 electrolyte between metallic copper electrodes serves as an experimental test system. Spatially resolved optical measurements are used to monitor the evolution of the ion concentration gradient in the electrolyte. Moreover, measured limited currents are related to computationally modeled concentration gradients. A constant parameterization of the diffusion coefficient, molar conductivity and ion transport number lead to a slight overestimation of the cathodic ion depletion and cell resistance, whereas a literature data based concentration dependent parameterization matches better to the measured data. The limited current is considered under a computational parameter variation and thereby related to the physicochemical impact of different electrolyte properties on the ion transport. This approach highlights the differences between purely diffusion limited currents and the limited current resulting from the combined electric field and diffusion driven ion motion. A qualitative schematic sketch of the physical mechanisms of the ion movement is presented to illustrate the current driven ion displacement in liquid electrolytes.

Nanoporous Cu (np-Cu) materials can be easily prepared by chemical dealloying of Zn-Cu alloys. Tuning the surface area, the number of defects, the content of the less noble metal, and the mass transport properties of the nanoporous materials allows us to control its chemical, physical and catalytic properties as well as its mechanical properties for different applications. We present how the formation of the np-Cu films is controlled by the annealing temperature and kind of electrolyte. The Zn-Cu alloy films were prepared by electrodeposition of Zn onto a Cu surface. After the thermal annealing at three different temperatures, the Zn-Cu alloy films were dealloyed in acidic and alkaline media. Based on our results obtained from SEM, EDX, XPS and XRD, we correlate the structural changes (ligament size, pore size, composition) with the experimental dealloying conditions (annealing temperature, kind of electrolyte) to better understand the dealloying processes for the np-Cu films.