COPPER AND ANTIMONY BASED MATERIAL AND ELECTRODE FOR THE SELECTIVE CONVERSION OF CARBON DIOXIDE TO CARBON MONOXIDE

The present invention relates to a copper and antimony based material, and an electrode obtained from this material, useful for the electrochemical reduction of carbon dioxide to carbon monoxide with high efficiency and selectivity

Optimizing the Performance of Low-Loaded Electrodes for CO2-to-CO Conversion Directly from Capture Medium: A Comprehensive Parameter Analysis

Gas-fed reactors for CO2 reduction processes are a solid technology to mitigate CO2 accumulation in the atmosphere. However, since it is necessary to feed them with a pure CO2 stream, a highly energy-demanding process is required to separate CO2 from the flue gasses. Recently introduced bicarbonate zero-gap flow reactors are a valid solution to integrate carbon capture and valorization, with them being able to convert the CO2 capture medium (i.e., the bicarbonate solution) into added-value chemicals, such as CO, thus avoiding this expensive separation process. We report here a study on the influence of the electrode structure on the performance of a bicarbonate reactor in terms of Faradaic efficiency, activity, and CO2 utilization. In particular, the effect of catalyst mass loading and electrode permeability on bicarbonate electrolysis was investigated by exploiting three commercial carbon supports, and the results obtained were deepened via electrochemical impedance spectroscopy, which is introduced for the first time in the field of bicarbonate electrolyzers. As an outcome of the study, a novel low-loaded silver-based electrode fabricated via the sputtering deposition technique is proposed. The silver mass loading was optimized by increasing it from 116 μg/cm2 to 565 μg/cm2, thereby obtaining an important enhancement in selectivity (from 55% to 77%) and activity, while a further rise to 1.13 mg/cm2 did not provide significant improvements. The tremendous effect of the electrode permeability on activity and proficiency in releasing CO2 from the bicarbonate solution was shown. Hence, an increase in electrode permeability doubled the activity and boosted the production of in situ CO2 by 40%. The optimized Ag-electrode provided Faradaic efficiencies for CO close to 80% at a cell voltage of 3 V and under ambient conditions, with silver loading of 565 μg/cm2, the lowest value ever reported in the literature so far

Production of Graphene Stably Dispersible in Ethanol by Microwave Reaction

Graphene is a 2D carbon material with peculiar features such as high electrical conductivity, high thermal conductivity, mechanical stability, and a high ratio between surface and thickness. Applications are continuously growing, and the possibility of dispersing graphene in low-boiling green solvents could reduce its global environmental impact. Pristine graphene can be dispersed in high concentration only in polar aprotic solvents that usually have high boiling points and high toxicity. For this reason, the oxidized form of graphene is always used, as it is easier to disperse and to subsequently reduce to reduced graphene oxide. However, compared to pristine graphene, reduced graphene oxide has more defects and has inferior properties respect to graphene. In this work, the polymerization of (diethyl maleate derivate) on graphene obtained by sonication was performed in a microwave reactor. The obtained material has good stability in ethanol even after a long period of time, therefore, it can be used to deposit graphene by mass production of inks or by casting and easy removal of the solvent. The thermal annealing by heating at 300–400 ◦C in inert atmosphere allows the removal of the polymer to obtain pristine graphene with a low number of defects

Electrochemical Reduction of {CO}2 With Good Efficiency on a Nanostructured Cu-Al Catalyst

Carbon monoxide (CO) and formic acid (HCOOH) are suggested to be the most convenient products from electrochemical reduction of CO2 according to techno-economic analysis. To date, tremendous advances have been achieved in the development of catalysts and processes, which make this research topic even more interesting to both academic and industrial sectors. In this work, we report nanostructured Cu-Al materials that are able to convert CO2 to CO and HCOOH with good efficiency. The catalysts are synthesized via a green microwave-assisted solvothermal route, and are composed of Cu2O crystals modified by Al. In KHCO3 electrolyte, these catalysts can selectively convert CO2 to HCOOH and syngas with H-2/CO ratios between 1 and 2 approaching one unit faradaic efficiency in a wide potential range. Good current densities of 67 and 130 mA cm(-2) are obtained at -1.0 V and -1.3 V vs. reversible hydrogen electrode (RHE), respectively. When switching the electrolyte to KOH, a significant selectivity up to 20% is observed for C2H4 formation, and the current densities achieve 146 and 222 mA cm(-2) at -1.0 V and -1.3 V vs. RHE, respectively. Hence, the choice of electrolyte is critically important as that of catalyst in order to obtain targeted products at industrially relevant current densities

Facile and scalable synthesis of Cu2O-SnO2 catalyst for the photoelectrochemical CO2 conversion

CO2 conversion into high-value-added products is becoming increasingly attractive to find substitutes for fossil-based ones and tackle the environmental crisis. Herein, a noble, simple, reproducible, and scalable Cu2O-SnO2 photo-electrocatalyst was synthesized and characterized. Coupling cuprous oxide with tin oxide allowed for protecting unstable Cu+1 species from photo-corrosion. Evidence of the SnO2 stabilization role were found via chronoamperometry tests under chopped light and XPS analysis. An optimized catalytic ink was developed to prepare the photocathodes. The CO2 photo-electroreduction tests demonstrated a prevalent production of CO and formate with Faradaic efficiencies of 35.47 % and 19.58 %, respectively, and a good system stability. Sunlight illumination demonstrated to play a major role to hinder H2 evolution and promote ≥C1+ products formation

Facile and scalable synthesis of Cu2O-SnO2 catalyst for the photoelectrochemical CO2 conversion

The conversion of the atmospheric CO2 to value-added compounds is more and more attractive to the scientific community, since natural sink cannot keep up with the constant anthropogenic emission and amplification processes. Recently, CO2 concentration in the atmosphere exceeds 410 ppm, and its growth has remained constant since the 50s[1]. Renewable and green approaches to CO2 recovery are aimed to minimize the worrying impact of its emission to the environment, and to drive the transition to a new circular economy approach in chemistry and energy production. Within the depicted scenario, electrochemical and photoelectrochemical CO2 reduction are being widely investigated as promising methods to transform CO2, under mild reaction conditions, into useful chemicals or fuels. For instance, alcohols, CO and HCOOH that can be exploited as renewable energy sources or as key intermediates for the chemical industry. Among the non-precious metal oxides, Cu2O is a cheap, abundant and intrinsically p-type semiconductor. Due to its narrow band gap (~ 2 eV) and the suitable positioning of conduction and valence bands, Cu2O is an ideal photocatalyst for CO2RR. Simultaneously, SnO2 is an n-type direct band-gap semiconductor with noticeable electron mobility together with an intrinsic stability. It openly transpires the dual role of Cu2O, as photoabsorber and forming a p-n junction with Tin Oxide. In this work, the synthesis of photoactive copper-tin-oxide-based catalyst was optimized by a co-precipitation method[2], employing Cu(NO3)2·3H2O and SnCl4∙5H2O into a stirred and heated reactor. A solution of Na2CO3 was added as a precipitant agent, while NaBH4 as the reducing one[3], in order to promote the Cu2O formation. The work-up protocol, based on copious MilliQ water washings, was implemented and finally optimized. The characterization step included Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Analysis (EDX) X-rays Diffraction Analysis(XRD), UV-Visible Spectroscopy analysis, among others, and allowed the morphological assessment, the porosity value estimation and the crystalline phase evaluation. With the latter, it has been found a correspondence to the cubic crystalline phase (cuprite) of Cu2O and consequently confirmation that the reduction process has been successfully carried out. The so obtained catalyst was then deposited it onto a GDL (Gas Diffusion Layer) and FTO-based substrates by spray coating of an ink containing: the catalysts, Vulcan carbon (to increase the electrode conductivity), Nafion as binder and Isopropanol as carrier. The photo-electrochemical activity for the CO2 reduction reaction was tested in the dark and under sunlight simulated conditions by means of Linear Sweep Voltammetry (LSV) and Chrono-Potentiometry (CP) analyses. Relevant current density (j) values of up to 40 mA/cm2 were observed, and from the products analysis during the CP a high Faradaic Efficiency to CO was obtained. The influence of the ink composition was accurately investigated in terms of interaction among all the components and with respect to the employed substrate, taking into account sun-light activity and stability of the prepared electrodes towards their future utilization in a device for the sun-driven CO2 conversion to high-added value products. AKCNOWLEDGMENT This work has received funding from the European Union’s Horizon 2020 Research and Innovation Action programme under the Project SunCoChem (Grant Agreement No 862192). [1] X. Lan, B. D. Hall, G. Dutton, J. Mühle, and J. W. Elkins. (2020). Atmospheric composition [in State of the Climate in 2018, Chapter 2: Global Climate]. [2] Schuth F., et al., Journal of Catalysis, (2008), 258 [3] Angew. Chem. Int. Ed. 10.1002/anie.20180896

Comparison of photocatalytic and transport properties of TiO2 and ZnO nanostructures for solar-driven water splitting

Titanium dioxide (TiO2) and zinc oxide (ZnO) nanostructures have been widely used as photo-catalysts due to their low-cost, high surface area, robustness, abundance and non-toxicity. In this work, four TiO2 and ZnO - based nanostructures, i.e. TiO2 nanoparticles (TiO2 NPs), TiO2 nanotubes (TiO2 NTs), ZnO nanowires (ZnO NWs) and ZnO@TiO2 core-shell structures, specifically prepared with a fixed thickness of about 1.5 μm, are compared for the solar-driven water splitting reaction, under AM1.5G simulated sunlight. A complete characterization of these photo-electrodes in their structural and photo-electrochemical properties was carried out. Both TiO2 NPs and NTs showed photo-current saturation reaching 0.02 and 0.12 mA/cm2, respectively, for potential values of about 0.3 and 0.6 V vs. RHE. In contrast, the ZnO NWs and the ZnO@TiO2 core-shell samples evidence a linear increase of the photocurrent with the applied potential, reaching 0.45 and 0.63 mA/cm2 at 1.7 V vs. RHE, respectively. However, under concentrated light conditions, the TiO2 NTs demonstrate a higher increase of the performance with respect to the ZnO@TiO2 core-shells. Such material dependent behaviours are discussed in relation with the different charge transport mechanisms and interfacial reaction kinetics, which were investigated through electrochemical impedance spectroscopy. The role of key parameters such as electronic properties, specific surface area and photo-catalytic activity on the performance of these materials are discussed. Moreover, proper optimization strategies are analyzed in view of increasing the efficiency of the best performing TiO2 and ZnO - based nanostructures, toward their practical application in a solar water splitting device

An improved method for quantitative magneto-optical analysis of superconductors

We report on the analysis method to extract quantitative local electrodynamics in superconductors by means of the magneto-optical technique. First of all, we discuss the calibration procedure to convert the local light intensity values into magnetic induction field distribution and start focusing on the role played by the generally disregarded magnetic induction components parallel to the indicator film plane (in-plane field effect). To account for the reliability of the whole technique, the method used to reconstruct the electrical current density distribution is reported, together with a numerical test example. The methodology is applied to measure local magnetic field and current distributions on a typical YBa2Cu3O7−x good quality film. We show how the in-plane field influences the MO measurements, after which we present an algorithm to account for the in-plane field components. The meaningful impact of the correction on the experimental results is shown. Afterwards, we discuss some aspects about the electrodynamics of the superconducting sample