Fundamental understanding of the influence of so‐called spectator electrolyte species on the catalytic activity of electrodes is considered as a relatively novel direction in electrocatalysis. Numerous recent examples show that seemingly inert electrolyte components drastically influence the performance of catalytic centers. Even alkali metal cations in aqueous electrolytes at high pH values can change the reaction turnover frequency by orders of magnitude, depending on their nature, from Li+ to Cs+. Here, we use several electrodes, namely Pt(polycrystalline), Pt(111), Pt(221), Ir(111), Au(111), and Ag(polycrystalline), in different alkali metal cation‐containing electrolytes to reveal their role in the hydrogen evolution reaction (HER). The HER activity trends of various Pt electrodes, irrespective of their surface structure, correlate with the hydration energy of the corresponding alkali metal cations present in the electrolyte (Li+>Na+>K+>Rb+>Cs+). The trend remains the same for the Ir(111), however, it is reversed for Au(111) and Ag(pc) electrocatalysts.

Metal oxides are important functional materials with a wide range of applications, especially in the field of electrocatalysis. However, quick and accurate assessment of their real electroactive surface area (ECSA), which is of paramount importance for the evaluation of their performance, remains a challenging task. Herein, we present a relatively simple strategy for an accurate in situ determination of the ECSA of commonly used metal oxide catalysts, namely Ni-, Co-, Fe-, Pt-, and Ir-based oxides. Similar to the well-established practice in electrocatalysis, the method is based on the phenomenon of specific adsorption. It uses the fact that at electrode potentials close to the onset of the oxygen evolution reaction, specifically adsorbed reaction intermediates manifest themselves through so called adsorption capacitance, which is unambiguously detectable using electrochemical impedance spectroscopy. We determined and calibrated these capacitances for common catalyst metal oxides using model thin films. Therefore, with simple impedance measurements, experimentalists can acquire the adsorption capacitance values and accurately estimate the real electroactive surface area of the above-mentioned oxide materials, including nanostructured electrocatalysts. Additionally, as illustrative examples, we demonstrate the application of the method for the determination of the ECSA of oxide catalyst nanoparticles.

Understanding the properties of the electrical double layer (EDL) is one of the interdisciplinary topics that plays a key role in the investigation of numerous natural and artificial systems. We present experimental evidence about the influence of the nature of the alkali metal cations on the EDL capacitance for two model electrodes, Pt(111) and Au(111), in 0.05 M AMClO ( AM: Li, Na, K, Rb, Cs) electrolytes using impedance spectroscopy measurements. Our data show that counterintuitively the differential EDL capacitance of both electrodes measured close to their potentials of zero charge increased linearly in the presence of alkali metal cations as Li < Na < K < Rb < Cs. We also estimated the effective concentrations of these cations at the EDL, which appeared ∼80 times higher than their bulk concentrations. We believe that these findings should be of importance for theoretical modeling of the EDL and better understanding and faster design of new functional systems for numerous applications.

High oxygen reduction (ORR) activity has been for many years considered as the key to many energy applications. Herein, by combining theory and experiment we prepare Pt nanoparticles with optimal size for the efficient ORR in proton-exchange-membrane fuel cells.O ptimal nanoparticle sizes are predicted near 1, 2, and 3nmb yc omputational screening.T oc orroborate our computational results,w eh ave addressed the challenge of approximately 1nms ized Pt nanoparticle synthesis with am etal-organic framework (MOF) template approach. The electrocatalyst was characterized by HR-TEM, XPS,a nd its ORR activity was measured using ar otating disk electrode setup.T he observed mass activities (0.87 AE 0.14 Amg Pt À1)a re close to the computational prediction (0.99 Amg Pt À1 ). We report the highest to date mass activity among pure Pt catalysts for the ORR within similar sizerange.The specific and mass activities are twice as high as the Tanaka commercial Pt/C catalysis.

In this perspective, key aspects for the identification, design and optimization of active centers at the surface of electrocatalysts are analyzed.