Unintended cation crossover influences CO2 reduction selectivity in Cu based zero gap electrolysers

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 device

Electrodeposition of palladium dotted nickel nanowire networks as a robust self supported methanol electrooxidation catalyst

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 amp; 8722;1 than a commercial carbon supported palladium nanoparticle catalyst and provides a much better long term stability during potential cyclin

Facile Synthesis of Hierarchical CuS and CuCo2S4 Structures from an Ionic Liquid Precursor for Electrocatalysis Applications

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 CuCo2S4 microflowers. Both routes provide high microflower yields of gt;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 amp; 8764;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 measurement

Poly ionic liquid nanovesicles via polymerization induced self assembly and their stabilization of Cu nanoparticles for tailored CO2 electroreduction

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 amp; 8764; 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 C1 products 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 product

Determining Structure Activity Relationships in Oxide Derived Cu Sn Catalysts During CO2 Electroreduction Using X Ray Spectroscopy

The development of earth abundant catalysts for selective electrochemical CO2 conversion is a central challenge. Cu amp; 63743;Sn bimetallic catalysts can yield selective CO2 reduction toward either CO or formate. This study presents oxide derived Cu amp; 63743;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 amp; 8776;70 at. consisting of both metallic Sn0 and Sn oxide species. Density functional theory simulations suggest that Sn amp; 948; 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 catalyst

Comparative Spectroscopic Study Revealing Why the CO2 Electroreduction Selectivity Switches from CO to HCOO at Cu Sn and Cu In Based Catalysts

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 pathway

Shape Controlled Electroless Plating of Hetero Nanostructures AgCu and AgNi Decorated Ag Nanoplates on Carbon Fibers as Catalysts for the Oxygen Evolution Reaction

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 amp; 946; NiOOH surface sites, which are the most relevant OER active Ni specie

Electrocatalyst Derived from Waste Cu Sn Bronze for CO2 Conversion into CO

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 produc