Insights from Operando and Identical Location (IL) Techniques on the Activation of Electrocatalysts for the Conversion of CO2: A Mini-Review

In this mini-review we compare two prototypical metal foam electrocatalysts applied to the transformation of CO2 into value-added products (e.g. alcohols on Cu foams, formate on Bi foams). A substantial improvement in the catalyst performance is typically achieved through thermal annealing in air of the as-deposited foam materials, followed by the electro-reduction of the pre-formed oxidic precursors prior or during the actual CO2 electrolysis. Utilizing highly insightful and sensitive complementary operando analytical techniques (XAS, XRD, and Raman spectroscopy) we demonstrate that this catalyst pre-activation process is entirely accomplished in case of the oxidized Cu foams prior to the formation of hydrocarbons and alcohols from the CO2. The actually active catalyst is therefore the metallic Cu derived from the precursor by means of its oxide electroreduction. Conversely, in their oxidic form, the Cu-based foam catalysts are completely inactive towards the CO2 reduction reaction (denoted ec-CO2RR). Oxidized Bi foams can be regarded as an excellent counter example to the above-mentioned Cu case as both metallic and the thermally derived oxidic Bi foams are highly active towards ec-CO2RR (formate production). Indeed, operando Raman spectroscopy reveals that CO2 electrolysis occurs upon its embedment into the oxidic Bi2O3 foam precursor, which itself undergoes partial transformation into an active sub-carbonate phase. The potential-dependent transition of sub-carbonate/oxides into the corresponding metallic Bi foam dictates the characteristic changes of the ec-CO2RR pathway. Identical location (IL) microscopic inspection of the catalyst materials, e.g. by means of scanning electron microscopy, demonstrates substantial morphological alterations on the nm length scale on the material surface as consequence of the sub-carbonate formation and the potential-driven oxide reduction into the metallic Bi foam. The foam morphology on a mesoscopic length scale (macroporosity) remains, by contrast, fully unaffected by these phase transitions

Anodic and Cathodic Platinum Dissolution Processes Involve Different Oxide Species

The degradation of Pt-containing oxygen reduction catalysts for fuel cell applications is strongly linked to the electrochemical surface oxidation and reduction of Pt. Here, we study the surface restructuring and Pt dissolution mechanisms during oxidation/reduction for the case of Pt(100) in 0.1 M HClO4 by combining operando high-energy surface X-ray diffraction, online mass spectrometry, and density functional theory. Our atomic-scale structural studies reveal that anodic dissolution, detected during oxidation, and cathodic dissolution, observed during the subsequent reduction, are linked to two different oxide phases. Anodic dissolution occurs predominantly during nucleation and growth of the first, stripe-like oxide. Cathodic dissolution is linked to a second, amorphous Pt oxide phase that resembles bulk PtO2 and starts to grow when the coverage of the stripe-like oxide saturates. In addition, we find the amount of surface restructuring after an oxidation/reduction cycle to be potential-independent after the stripe-like oxide has reached its saturation coverage.Funding is acknowledged from Deutsche Forschungsgemeinschaft for OMM and SC (project number 418603497), for OMM by the German Federal Ministry of Education and Research (BMBF) via project 05K19FK3, and for DAH by the NSERC (grant RGPIN-2017-04045). FCV acknowledges that the grants PID2021-127957NB-I00 and TED2021-132550B-C21 were funded by MCIN/AEI/ 10.13039/501100011033 and by the European Union. The use of supercomputing facilities at SURFsara was sponsored by NWO Physical Sciences, with financial support by NWO. Open Access funding enabled and organized by Projekt DEAL

Departure from solid solution behavior in double perovskites

Mixed ionic electronic conducting oxides (MIEC) serve a plethora of electrochemical applications such as cathodes for solid oxide electrochemical cells and oxygen evolution reaction catalysts for water splitting. These applications rely to a large extent on the MIEC’s ability for electron and/or ion transfer across the solid/gas or solid/liquid interface. The efficacy of these reactions being governed by the surface defect chemistry and electronic structure, rational design of the (surface) chemistry presents itself as an auspicious path to tune these properties towards optimal device performance. Please click Additional Files below to see the full abstract

The capping agent is the key: Structural alterations of Ag NPs during CO2 electrolysis probed in a zero-gap gas-flow configuration

We apply silver nanoparticles (Ag NPs) as catalysts of CO2reduction in a zero-gap gas-flow electrolyser.Ag NPs stabilized by different ligands —branched polyethylenimine (BPEI), polyvinylpyrrolidone (PVP),polyethylene glycol (PEG), and citrate— are used in the experiments. The as-prepared NPs have almostidentical initial size distributions, yet their catalytic performance, in terms of achievable current andCO selectivity, is different. During electrolysis all Ag NPs exhibit unambiguous morphology changes;the degradation pathway they follow, however, markedly depends on the chemical nature of the cappingagent stabilizing them. Scanning electron micrographs obtained before and after constant-charge elec-trolyses carried out at different potentials reveal that amongst the studied ligands, BPEI seems to bethe most effective stabilizer of Ag NPs; in turn, however, BPEI also limits CO formation the most. In caseof PVP, mostly corrosion (particle shrinkage) is observed at practically relevant electrolysing potentials,while the application of PEG leads more to particle coalescence. Ostwald ripening seems to appear only athigh applied (H2forming) potentials in case of the three afore-mentioned ligands while in case of citrateit becomes significant already at mild (CO forming) voltages. By studying the effects of capping agentremoval and exchange we demonstrate that apart from ligands directly attached to the Ag NPs, alsothe excess of capping agents (adsorbed on the electrode surface) plays a decisive role in determiningthe extent and mode of catalyst degradation. The results of SEM-based particle sizing are also confirmedby synchrotron based wide-angle X-ray scattering measurements that provide further insight into theevolution of crystallite size and lattice strain in the applied Ag NPs during electrolysis

Combined scanning probe microscopy and x-ray scattering instrument for in situ catalysis investigations

Catalysis and Surface Chemistr

Usage of digitalization in business

Téma bakalářské práce je Digitalizace v byznysu. Cílem této práce je za pomoci teoretických poznatků a získaných statistických dat zhodnotit digitalizační projekt společnosti a podat zlepšovací návrhy. Teoretická část definuje základní pojmy digitalizace a představuje druhy digitalizace, přínosy a rizika. Dále pak představuje společnost, s kterou byla tato práce zpracovávána. Praktická část se zabývá benchmarkingem vybraných konkurenčních společností a statistickou analýzou dat získaných z dotazníku. V závěru práce je zhodnocení a na základě provedených šetření je formulováno několik řešení pro zvýšení popularizace nepopulárních voleb zákazníků.ObhájenoThe theme of this Bachelor thesis is Usage of digitalization in business. The aim was to evaluate digitalization project of the company and give innovative suggestions based on theoretical knowledge and gathered statistical data. Theoretical part is defining basic concept of digitalization and is introducing types of digitalization and it benefits and risks. Afterwards it is introducing the company that was used to create this thesis. Practical part is presenting benchmarking of chosen competitive companies and statistical research of acquired data. In the conclusion of the thesis there is evaluation based on research that was done and then few solutions on how to make the unpopular options more popular

Usage of digitalization in business

Téma bakalářské práce je Digitalizace v byznysu. Cílem této práce je za pomoci teoretických poznatků a získaných statistických dat zhodnotit digitalizační projekt společnosti a podat zlepšovací návrhy. Teoretická část definuje základní pojmy digitalizace a představuje druhy digitalizace, přínosy a rizika. Dále pak představuje společnost, s kterou byla tato práce zpracovávána. Praktická část se zabývá benchmarkingem vybraných konkurenčních společností a statistickou analýzou dat získaných z dotazníku. V závěru práce je zhodnocení a na základě provedených šetření je formulováno několik řešení pro zvýšení popularizace nepopulárních voleb zákazníků.ObhájenoThe theme of this Bachelor thesis is Usage of digitalization in business. The aim was to evaluate digitalization project of the company and give innovative suggestions based on theoretical knowledge and gathered statistical data. Theoretical part is defining basic concept of digitalization and is introducing types of digitalization and it benefits and risks. Afterwards it is introducing the company that was used to create this thesis. Practical part is presenting benchmarking of chosen competitive companies and statistical research of acquired data. In the conclusion of the thesis there is evaluation based on research that was done and then few solutions on how to make the unpopular options more popular

Small-angle scattering by supported nanoparticles: exact results and useful approximations

In functional materials, nanoparticles are often dispersed in a porous support for the purpose of stabilizing them. This makes their characterization by small-angle scattering challenging because the signal comprises contributions from the nanoparticles of interest, from the inert support and from their crosscorrelation. Exact analytical expressions for all three contributions are derived in the case of a Gaussian-field model of the porous support, with nanoparticles randomly distributed over the surface. For low nanoparticle loading, the expressions simplify to the addition of properly scaled support and particle scattering. For higher loadings, however, the cross-correlation cannot be ignored. Two approximations are introduced, which capture correlation effects in cases where the pores of the support are much larger or only slightly larger than the nanoparticles. The methods of the paper are illustrated with the smallangle X-ray scattering analysis of hollow metallic nanoparticles supported on porous carbon