Electrochemically converting carbon dioxide into useful products is a promising approach to combat climate change by reducing our reliance on fossil fuels and promoting a sustainable carbon cycle. The operation of membrane electrode assemblies within gas diffusion cells facilitates the efficient reduction of CO2 at rates relevant to industrial applications. However, their long-term stability is often limited by formation of solid precipitates in the cathode pores. This is a consequence of a combination of 1) local alkalization due to the electrochemical reaction, 2) generation of (bi)carbonate by chemical reaction of CO2 with the alkaline electrolyte, and 3) the presence of alkali metal cations. In catholyte-free, zero-gap cells using anion exchange membranes, the presence of electrolyte cations at the cathode is the result of unintended crossover from the anolyte, and a detailed understanding of the factors enabling this crossover is lacking. Here we show that the anolyte concentration governs the flux of cation migration through the membrane, and this substantially influences the behaviours of copper catalysts in catholyte-free CO2 electrolyzers. Our findings highlight the substantial impact of cation effects, including unintended crossover, even in catholyte-free cells, on reaction pathways. This aspect should be considered in the future development of catalysts and devices. As an outlook a more in-depth knowledge with the help of operando measurements could help to understand and manage cation crossover for optimizing the performance, selectivity, and durability of these electrochemical systems.

Membrane electrode assemblies in gas diffusion cells enable CO2 reduction at industrially relevant rates, yet their long-term operational stability is often limited by the formation of solid precipitates (e.g. K2CO3) in the cathode pores. This is a consequence of a combination of 1) local alkalization due to the electrochemical reaction, 2) generation of (bi)carbonate by chemical reaction of CO2 with the alkaline electrolyte, and 3) the presence of alkali metal cations. In catholyte-free, zero-gap cells using anion exchange membranes, the presence of electrolyte cations at the cathode is the result of unintended crossover from the anolyte, and a detailed understanding of the factors enabling this crossover is lacking. Here we show that the anolyte concentration governs the flux of cation migration through the membrane, and this substantially influences the behaviors of copper catalysts in catholyte-free CO2 electrolysers. Systematic variation of the anolyte ionic strength (using aqueous KOH or KHCO3) correlated with drastic changes in the observed product selectivity – most notably, at low ionic strength, Cu catalysts produced predominantly CO, in contrast to the mixture of C2+ products typically observed on Cu. In this talk, we examine the factors influencing ion crossover and the resulting effects on catalyst structure and activity, under conditions of both CO2 and CO reduction. Operando X-ray absorption spectroscopy and quasi in situ X-ray photoelectron spectroscopy were used to study how the catalyst is affected by operation conditions. Our results show that even in catholyte-free cells, cation effects (including unintended ones) can significantly influence reaction pathways, and this must be considered in future development of catalysts and devices.

Herein, we report a straightforward, scalable synthetic route towards poly(ionic liquid) (PIL) homopolymer nanovesicles (NVs) with a tunable particle size of 50 to 120 nm and a shell thickness of 15 to 60 nm via one-step free radical polymerization induced self-assembly. By increasing monomer concentration for polymerization, their nanoscopic morphology can evolve from hollow NVs to dense spheres, and finally to directional worms, in which a multilamellar packing of PIL chains occurred in all samples. The transformation mechanism of NVs’ internal morphology is studied in detail by coarse-grained simulations, revealing a correlation between the PIL chain length and the shell thickness of NVs. To explore their potential applications, PIL NVs with varied shell thickness are in situ functionalized with ultra-small (1 ∼ 3 nm in size) copper nanoparticles (CuNPs) and employed as electrocatalysts for CO2 electroreduction. The composite electrocatalysts exhibit a 2.5-fold enhancement in selectivity towards C1products (e.g., CH4), compared to the pristine CuNPs. This enhancement is attributed to the strong electronic interactions between the CuNPs and the surface functionalities of PIL NVs. This study casts new aspects on using nanostructured PILs as new electrocatalyst supports in CO2 conversion to C1 products.

Membrane electrode assemblies enable CO2 electrolysis at industrially relevant rates, yet their operational stability is often limited by formation of solid precipitates in the cathode pores, triggered by cation crossover from the anolyte due to imperfect ion exclusion by anion exchange membranes. Here we show that anolyte concentration affects the degree of cation movement through the membranes, and this substantially influences the behaviors of copper catalysts in catholyte-free CO2 electrolysers. Systematic variation of the anolyte (KOH or KHCO3) ionic strength produced a distinct switch in selectivity between either predominantly CO or C2+ products (mainly C2H4) which closely correlated with the quantity of alkali metal cation (K+) crossover, suggesting cations play a key role in C-C coupling reaction pathways even in cells without discrete liquid catholytes. Operando X-ray absorption and quasi in situ X-ray photoelectron spectroscopy revealed that the Cu surface speciation showed a strong dependence on the anolyte concentration, wherein dilute anolytes resulted in a mixture of Cu+ and Cu0 surface species, while concentrated anolytes led to exclusively Cu0 under similar testing conditions. These results show that even in catholyte-free cells, cation effects (including unintentional ones) significantly influence reaction pathways, important to consider in future development of catalysts and devices.

To address the challenge of selectivity toward single products in Cu-catalyzed electrochemical CO2 reduction, one strategy is to incorporate a second metal with the goal of tuning catalytic activity via synergy effects. In particular, catalysts based on Cu modified with post-transition metals (Sn or In) are known to reduce CO2 selectively to either CO or HCOO– depending on their composition. However, it remains unclear exactly which factors induce this switch in reaction pathways and whether these two related bimetal combinations follow similar general structure–activity trends. To investigate these questions systematically, Cu–In and Cu–Sn bimetallic catalysts were synthesized across a range of composition ratios and studied in detail. Compositional and morphological control was achieved via a simple electrochemical synthesis approach. A combination of operando and quasi-in situ spectroscopic techniques, including X-ray photoelectron, X-ray absorption, and Raman spectroscopy, was used to observe the dynamic behaviors of the catalysts’ surface structure, composition, speciation, and local environment during CO2 electrolysis. The two systems exhibited similar selectivity dependency on their surface composition. Cu-rich catalysts produce mainly CO, while Cu-poor catalysts were found to mainly produce HCOO–. Despite these similarities, the speciation of Sn and In at the surface differed from each other and was found to be strongly dependent on the applied potential and the catalyst composition. For Cu-rich compositions optimized for CO production (Cu85In15 and Cu85Sn15), indium was present predominantly in the reduced metallic form (In0), whereas tin mainly existed as an oxidized species (Sn2/4+). Meanwhile, for the HCOO–-selective compositions (Cu25In75 and Cu40Sn60), the indium exclusively exhibited In0 regardless of the applied potential, while the tin was reduced to metallic (Sn0) only at the most negative applied potential, which corresponds to the best HCOO– selectivity. Furthermore, while Cu40Sn60 enhances HCOO– selectivity by inhibiting H2 evolution, Cu25In75 improves the HCOO– selectivity at the expense of CO production. Due to these differences, we contend that identical mechanisms cannot be used to explain the behavior of these two bimetallic systems (Cu–In and Cu–Sn). Operando surface-enhanced Raman spectroscopy measurements provide direct evidence of the local alkalization and its impact on the dynamic transformation of oxidized Cu surface species (Cu2O/CuO) into a mixture of Cu(OH)2 and basic Cu carbonates [Cux(OH)y(CO3)y] rather than metallic Cu under CO2 electrolysis. This study provides unique insights into the origin of the switch in selectivity between CO and HCOO– pathways at Cu bimetallic catalysts and the nature of surface-active sites and key intermediates for both pathways.

The development of earth-abundant catalysts for selective electrochemical CO2conversion is a central challenge. CuSn bimetallic catalysts can yield selective CO2reduction toward either CO or formate. This study presents oxide-derived CuSn catalysts tunable for either product and seeks to understand the synergetic effects between Cu and Sn causing these selectivity trends. The materials undergo significant transformations under CO2 reduction conditions, and their dynamic bulk and surface structures are revealed by correlating observations from multiple methods—X-ray absorption spectroscopy for in situ study, and quasi in situ X-ray photoelectron spectroscopy for surface sensitivity. For both types of catalysts, Cu transforms to metallic Cu0 under reaction conditions. However, the Sn speciation and content differ significantly between the catalyst types: the CO-selective catalysts exhibit a surface Sn content of 13 at. % predominantly present as oxidized Sn, while the formate-selective catalysts display an Sn content of ≈70 at. % consisting of both metallic Sn0 and Sn oxide species. Density functional theory simulations suggest that Snδ+ sites weaken CO adsorption, thereby enhancing CO selectivity, while Sn0 sites hinder H adsorption and promote formate production. This study reveals the complex dependence of catalyst structure, composition, and speciation with electrochemical bias in bimetallic Cu catalysts.

This study addresses the potential of combining multiple electroless plating reactions for homogeneous decoration of three-dimensional carbon fibers (CFs) with shape-controlled AgNi and AgCu bimetallic nanostructures. Morphology, crystal structure, and composition of the obtained bimetallic nanostructures were systemically examined by various spectroscopic and microscopic techniques including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The electrocatalytic performance of the synthesized materials was investigated for the oxygen evolution reaction (OER). AgCu and AgNi bimetallic surfaces showed superior activity and stability compared to pristine Ag, Ni, or Cu. These observed enhancements on the bimetallic nanostructures are attributed to the synergistic effect between the elements present. AgNi nanoplate-decorated CFs exhibited the highest activity toward OER, which is attributed to the key role of Ag in stabilizing and increasing the number of β-NiOOH surface sites, which are the most relevant OER-active Ni species.

To sustainably exist within planetary boundaries, we must greatly curtail our extraction of fuels and materials from the Earth. This requires new technologies based on reuse and repurposing of material already available. Electrochemical conversion of CO2 into valuable chemicals and fuels is a promising alternative to deriving them from fossil fuels. But most metals used for electrocatalysis are either endangered or at serious risk of limitation to their future supply. Here, we demonstrate a combined strategy for repurposing of a waste industrial Cu–Sn bronze as a catalyst material precursor and its application toward CO2 reuse. By a simple electrochemical transfer method, waste bronzes with composition Cu14Sn were anodically dissolved and cathodically redeposited under dynamic hydrogen bubble template conditions to yield mesoporous foams with Cu10Sn surface composition. The bimetal foam electrodes exhibited high CO2 electroreduction selectivity toward CO, achieving greater than 85% faradaic efficiency accompanied by a considerable suppression of the competing H2 evolution reaction. The Cu–Sn foam electrodes showed good durability over several hours of continuous electrolysis without any significant change in the composition, morphology, and selectivity for CO as a target product.

Mass activity and long-term stability are two major issues in current fuel cell catalyst designs. While supported catalysts normally suffer from poor long-term stability but show high mass activity, unsupported catalysts tend to perform better in the first point while showing deficits in the latter one. In this study, a facile synthesis route towards self-supported metallic electrocatalyst nanoarchitectures with both aspects in mind is outlined. This procedure consists of a palladium seeding step of ion track-etched polymer templates followed by a nickel electrodeposition and template dissolution. With this strategy, free-standing nickel nanowire networks which contain palladium nanoparticles only in their outer surface are obtained. These networks are tested in anodic half-cell measurements for demonstrating their capability of oxidising methanol in alkaline electrolytes. The results from the electrochemical experiments show that this new catalyst is more tolerant towards high methanol concentrations (up to 5molL−1">) than a commercial carbon supported palladium nanoparticle catalyst and provides a much better long-term stability during potential cycling.

Во овој труд е презентиран нов, хемиски метод за визуелизација на латентни отпечатоци од прсти на површина од месинг од неиспукани куршуми. Методот е базиран на селективна хемиска депозиција на олово (II) сулфид во просторот помеѓу папиларните линии на површина. Постапката е едноставна и се состои од краткотрајно потопување на куршумите во раствор за визуелизација. Растворот за визуелизација на отпечатоците е приготвен со мешање на водни раствори од олово (II) ацетат, натриум хидроксид, триетанол амин и тиоуреа. Хемискиот процес се одвива во алкална средина и умерено загревање. Испитувањето на хемискиот состав на депонираниот материјал, беше извршено со прашкова рендгенска дифракција (XRPD). Дизајнирањето на овој метод беше спроведено со употреба на значителен број на примероци од неиспукани куршуми, при што беше испитувана и можноста за визуелизација на релативно стари отпечатоци. Притоа, успешно беа визуелизирани отпечатоци кои беа нанесени пред околу 2 години. Предложениот метод е релативно едноставен за изведување, што го прави потенцијално корисен при форензички испитувања. Клучни зборови: латентни отпечатоци, олово (II) сулфид, неиспукани куршуми, форензичка хемија, хемиска депозиција

In the field of electrochemical reduction of CO2 (CO2ER) Cu and oxide derived OD-Cu electrocatalysts have been widely studied due to their unique capability to produce high added value products, such as CO, hydrocarbons and alcohols, albeit with relatively low selectivity.1 Cu-M bimetallic catalysts are a promising approach to break scaling relations among key intermediates and modulate the CO2ER selectivity. In the past 5 years, several studies on the CO2ER activity of Cu-Sn bimetallic catalysts have demonstrated remarkably high selectivities towards CO2,3 or formate.4,5In general, comparison of several studies employing various Cu-Sn stoichiometries shows that Sn-poor catalysts are typically selective towards CO production, while Sn-rich catalysts favor formate (HCOO⁻). However, the specific optimal compositions leading to high activity towards CO or formate vary significantly among reports. 6–8 Furthermore, the mechanistic origins of the selectivity differences among Cu-Sn catalysts remains a topic of debate. Trends in product selectivity have been ascribed to aspects including composition, lattice effects,7charge redistribution among metals in alloy structures,9 oxidation states,4,8 and the resulting effects on adsorption strength of key intermediates (e.g. *COOH, *OCHO, *CO, *H) directing selectivity among H2, CO and HCOO⁻. A comparison of the relevant literature has allowed us to establish common trends in CO2ER activity of Cu-Sn of various morphologies, synthetic procedures and speciation (Oxide derived vs Alloy materials) and identify points of controversy and key open questions that might help unifying the understanding of the activation of CO2 on Cu-Sn bimetallics. At the center of the debate is the persistence of oxidized metal sites during CO2ER and the precise nature of the active site. A major challenge in this regard, is the complex dependence of catalyst structure and composition with applied electrochemical bias. In this context, we explore X-ray spectroscopies as powerful tools to investigate the chemical environment and oxidation state of metal sites Sn and Cu in bimetallic electrocatalysts. By correlating diverse X-ray spectroscopy methods (soft and hard X-ray absorption (XAS) techniques, as well as X-ray photoelectron spectroscopy (XPS)), complementary information can be obtained on the chemical environment of metal sites in an electrocatalyst bulk and surface. We report our study on the dependence of structure and composition on applied electrochemical potential in Sn-functionalized Cu catalysts, achieved by combining in situ hard XAS, ex situ soft-XAS and XPS toward building a more complete picture of this model catalyst system.

A new chemical method for visualization of latent fingermarks on unfired cartridge cases is reported in this research. The method is based on two-step immersion of the cartridge cases in aqueous solutions of sulfuric acid and acidified sodium thiosulfate at room temperature. The chemical reactions that are occurring on the cartridge case's surface are leading to deposition of material in the furrows between the papillary line ridges thus visualizing the latent fingermark. The qualitative chemical composition of the as-deposited material was studied using X-ray powder diffraction analysis thus revealing that it corresponds to a low-crystalline hexagonal chalcocite phase cuprous sulfide (Cu2S). The performance of the method was studied on fresh and aged fingermarks, and according to the results, it can visualize latent fingermarks that are up to 9 months old. The newly proposed method provides good performance considering the most important qualitative and quantitative parameters that describe each fingermark, that is, satisfactory contrast between the papillary line ridges and the background furrows, possibility of recognizing the pattern of each fingermark (arch, loop, and whorl), clarity and continuity of the friction ridges, and clarity of the second level characteristics and features. The proposed method is simple, fast, inexpensive, and reliable.

Covellite-phase CuS and carrollite-phase CuCo2S4 nano- and microstructures were synthesized from tetrachloridometallate-based ionic liquid precursors using a novel, facile, and highly controllable hot-injection synthesis strategy. The synthesis parameters including reaction time and temperature were first optimized to produce CuS with a well-controlled and unique morphology, providing the best electrocatalytic activity toward the oxygen evolution reaction (OER). In an extension to this approach, the electrocatalytic activity was further improved by incorporating Co into the CuS synthesis method to yield CuCo2S4microflowers. Both routes provide high microflower yields of >80 wt %. The CuCo2S4 microflowers exhibit a superior performance for the OER in alkaline medium compared to CuS. This is demonstrated by a lower onset potential (∼1.45 V vs RHE @10 mA/cm2), better durability, and higher turnover frequencies compared to bare CuS flowers or commercial Pt/C and IrO2 electrodes. Likely, this effect is associated with the presence of Co3+ sites on which a better adsorption of reactive species formed during the OER (e.g., OH, O, OOH, etc.) can be achieved, thus reducing the OER charge-transfer resistance, as indicated by X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy measurements.

A new chemical method for visualization of latent fingermarks on thermal paper, based on a treatment with nitrogen dioxide (NO2) gas, is presented in this work. The gas is generated by a reaction between zinc and diluted nitric acid in a closed chamber. This newly proposed method does not require fingermark’s fixation reagent after the treatment with NO2 i.e. the visualized fingermark remains permanent for more than one week and without any changes in its quality. The general visualization mechanism is based on providing acidic conditions in order to induce tautomeric transformation of the leuco dye’s molecules in the thermal layer, accompanied by a color change of the papillary lines throughout the whole fingermark. The NO2 method provides satisfactory contrast between the visualized fingermarks and the background surface i.e. thermal layer. The visualized fingermarks are qualified with high clarity and continuity of the friction ridges, and clarity of the 2nd level characteristics. The proposed method was evaluated by dactyloscopic comparison of the number of 2nd level characteristics and according to the results it can be exemplified with high identification capacity. The proposed method is simple, safe, cheap, non-destructive, non-time consuming, applicable for visualization of aged fingermarks, and potentially applicable under terrain (field) conditions in real forensic casework.

The present study describes development of a non–enzymatic amperometric sensor for detection of H2O2 based on MnCO3 thin film electrodes. The film was deposited on electroconductive FTO coated glass substrates using simple chemical bath deposition method. The phase composition of the thin film was confirmed by X-ray diffraction analysis. The electrochemical properties and the sensor sensitivity towards H2O2 were examined using cyclic voltammetry and chronoamperometry in 0.1 M phosphate buffer solution with pH = 7.5. It was revealed that the sensing mechanism is based on electrocatalytic oxidation of H2O2, involving Mn species as redox mediators. According to the results, the best sensor response towards H2O2 was found at E = +0.25 V, with detection limit and sensor sensitivity of 10.0 µM and 2.64 µA cm–2 mM–1 (for the range of 0.09–1.8 mM), respectively, associated with R2 = 0.999.

A new cost-effective, simple, and reproducible chemical method for the visualization of latent fingerprints on unfired cartridge cases and also on flat metal surfaces (made of zinc-plated steel. stainless steel, lead. copper. and aluminum) has been designed. This chemical method is based on a deposition of potassium birnessite on the uncontaminated metal surface in the valleys between the fingerprint ridges. The chemical deposition is performed by successive immersion (dip coating) of the cartridge cases into aqueous solutions of manganese (II) chloride and potassium permanganate. The deposited material is examined with x-ray powder diffraction analysis, and the visualization of the fingerprints is characterized on the first, second, and third level with high-resolution photography. This research was carried out on samples of 30 unfired cartridge cases of different calibers and different origins and on 5 different metal surfaces, resulting in the visualization of the latent fingerprints with very good contrast. The designed method is applicable for forensic investigations.

An optimized chemical bath method is applied to obtain well-structured thin films with composition Na0.33V2O5·nH2O (n = 1 and 1.3). The method is based on a controlled precipitation reaction that takes place in the system of sodium metavanadate and diethyl sulfate at 85 °C. The film structure, morphology and the changes occurring during prolonged aging are examined by XRD, IR spectroscopy, TG-DTA, SEM and AFM. The electrochemical and electrochromic properties are studied by cyclic voltammetryand UV–vis spectroscopy. The as-deposited thin films are characterized with high optical transmittance varying between 40 and 70% at the 500 nm visible region in dependence on film thickness. The Na0.33V2O5·nH2O thin films exhibit stable electrochemical cycling combined with relatively high electrochromic activity. The reproducibility of the transmittance variance of 55% after 500 cycles in the electrochromic cell is a promising result for the potential application of Na0.33V2O5·nH2O thin films in electrochromic devices.

This article presents a new safe, cheap and attractive microscale gas generation method that is expected to find place in the primary and secondary schools. Microscale gas generation apparatus consists of plastic syringe, Beral pipette and small plastic or glass test tube on a stand. The pipette has a role of a chemical reactor, which generatesgas and delivers it into a test tube where reaction takes place. Gas generation is based on chemical reaction between liquid substance, which is inserted with syringe and needle into the pipette bulb with liquid or solid substance previously placed in it. A large number of interesting and vivid microscale experiments can be performed using this kind of apparatus and many gases can be generated.

A new chemical bath method for deposition of manganese(II) carbonate thin film on electroconductive FTO glass substrates is designed. The homogeneous thin films with thickness in the range of 70 to 500 nm are deposited at about 98 °C from aqueous solution containing urea and MnCl2. The chemical process is based on a low temperature hydrolysis of the manganese complexes with urea. Three types of films are under consideration: as-deposited, annealed and electrochemically transformed thin films. The structure of the films is studied by XRD, IR and Raman spectroscopy. Electrochemical and optical properties are examined in eight different electrolytes (neutral and alkaline) and the best results are achieved in two component aqueous solution of 0.1 M KNO3 and 0.01 M KOH. It is established that the as-deposited MnCO3film undergoes electrochemically transformation into birnessite-type manganese(IV) oxide films, which exhibit electrochromic color changes (from bright brown to pale yellow and vice versa) with 30% difference in the transmittance of the colored and bleached state at 400 nm.