The aim to produce highly active, selective, and long-lived electrocatalysts by design drives major research efforts toward gaining fundamental understanding of the relationship between material properties and their catalytic performance. Surface characterization tools enable to assess atomic scale information on the complexity of electrocatalyst materials. Advancing electrochemical methodologies to adequately characterize such systems was less of a research focus point. In this Review, we shed light on the ability to gain fundamental insights into electrocatalysis from a complementary perspective and establish corresponding design strategies. These may rely on adopting the perceptions and models of other subareas of electrochemistry, such as corrosion, battery research, or electrodeposition. Concepts on how to account for and improve mass transport, manage gas bubble release, or exploit magnetic fields are highlighted in this respect. Particular attention is paid to deriving design strategies for nanoelectrocatalysts, which is often impeded, as structural and physical material properties are buried in electrochemical data of whole electrodes or even devices. Thus, a second major approach focuses on overcoming this difference in the considered level of complexity by methods of single-entity electrochemistry. The gained understanding of intrinsic catalyst performance may allow to rationally advance design concepts with increased complexity, such as three-dimensional electrode architectures. Many materials undergo structural changes upon formation of the working catalyst. Accordingly, developing "precatalysts" with low hindrance of the electrochemical transformation to the active catalyst is suggested as a final design strategy.

What was the biggest surprise?When analyzingt he currentr esponse of commercial potentiostats, we realized that most of them employ surprisingly strong low pass filtering. This is usually appropriate in electrochemistry.H owever, in nanoimpact studies, currents ignals of low amplitude ( nA) and short duration ( ms) are concerned. Hence, shape and duration of collision peaks may be significantly altered, which may causem isinterpretationo fr eaction mechanisms and extraction of incorrect kinetic information.Invited for this month'sc over picturei st he group of Prof. Dr.K ristinaT schulik from Ruhr University Bochum( Germany). The cover picture shows the alteration of ac urrent signal caused by the electronic filtering implemented in potentiostats. These filter effects are uncovereda nd as imple method is provided for electrochemists to test and validate their experimental setup. This is particularly important for transients ingle-entity electrochemistry,w hich requires low current measurements at high time resolution. Read the full text of the Articleat10.1002/celc.201800738.

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Invited for this month's cover picture is the group of Prof. Dr. Kristina Tschulik from Ruhr University Bochum (Germany). The cover picture shows the alteration of a current signal caused by the electronic filtering implemented in potentiostats. These filter effects are uncovered and a simple method is provided for electrochemists to test and validate their experimental setup. This is particularly important for transient single‐entity electrochemistry, which requires low current measurements at high time resolution. Read the full text of the Article at https://doi.org/10.1002/celc.201800738.

Dedicated to Wolfgang Schuhmann in honour of his 65 th birthdaySingle entity electrochemistry is employed to gain insights into ion solvation in solvent mixtures. To this end, the time required for the oxidation of individual indicator nanoparticles to sparingly soluble products is used to probe ionic diffusion, and hence gain new insights into the solvation properties of solvent mixtures. Herein, water-ethanol or water-methanol mixtures of different compositions are analyzed following this new approach, using silver nanoparticle oxidation in the presence of chloride and iodide as a complementary indicator reaction. For increasing concentrations of the bulkier alcohol molecules in the mixtures with water, an increasing content of alcohol molecules in the halide's solvation shell is detected by the observation of hindered halide diffusion. The extent of this solvent replacement is shown to scale with the charge density of the ions and the experimental results are rationalized with respect to literature-derived thermodynamic data, highlighting the ability of single entity electrochemistry to explore solvation in solvent mixtures.

Electrochemical analysis relies on precise measurement of electrical signals, yet the distortions caused by potentiostat circuitry and filtering are rarely addressed. Elucidation of these effects is essential for gaining insights behind sensitive low-current and short-duration electrochemical signals, e.g., in single-entity electrochemistry. We present a simulation approach utilizing the Electrical Simulation Program with Integrated Circuit Emphasis (SPICE), which is extensively used in electronic circuit simulations. As a proof-of-concept, we develop a universal electrical circuit model for single nanoparticle impact experiments, incorporating potentiostat and electronic filter circuitry. Considering these alterations, the experimentally observed transients of silver nanoparticle oxidation were consistently shorter and differently shaped than those predicted by established models. This reveals the existence of additional processes, e.g., migration, partial or asymmetric oxidation. These results highlight the SPICE approach's ability to provide valuable insights into processes occurring during single-entity electrochemistry, which can be applied to various electrochemical experiments, where signal distortions are inevitable.

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Single particle electrochemical oxidation of poly(vinylpyrrolidone)-capped silver nanoparticles at a microdisk electrode was investigated as a function of particle shape (spheres, cubes, and plates) in potassium nitrate and potassium hydroxide solutions. In potassium nitrate, extreme anodic potentials (≥1500 mV vs. Ag/AgCl (3 M KCl)) were necessary to achieve oxidation, while lower anodic potentials were required in potassium hydroxide (≥900 mV vs. Ag/AgCl (saturated KCl)). Upon oxidation, silver oxide is formed, readily catalyzing water oxidation, producing a spike-step current response. The spike duration for each particle was used to probe effects of particle shape on the oxidation mechanism, and is substantially shorter in nitrate at the large overpotentials than in hydroxide solution. The integration of current spikes indicate initial oxidation to Ag(I) in a mixed-valance complex. In both electrolytes, the rate of silver oxidation strongly depends on silver content of the nanoparticles, rather than the shape-dependent variable–surface area. The step height, which reflects rate of water oxidation, also tracks the silver content more so than shape. Results were compared to those from less-protected citrate-capped particles and suggest that contributions of the polymer capping ligand to kinetic barriers to oxidation are negligible under these conditions.