Ultra-Thin Plasma-Polymerized Functional Coatings for Biosensing: Polyacrylic Acid, Polystyrene and Their Co-Polymer

Recently, many efforts have been done to chemically functionalize sensors surface to achieve selectivity towards diagnostics targets, such as DNA, RNA fragments and protein tumoural biomarkers, through the surface immobilization of the related specific receptor. Especially, some kind of sensors such as microcantilevers (gravimetric sensors) and one-dimensional photonics crystals (optical sensors) able to couple Bloch surface waves are very sensitive. Thus, any kind of surface modifications devoted to functionalize them has to be finely controlled in terms of mass and optical characteristics, such as refractive index, to minimize the perturbation, on the transduced signal, that can affect the response sensitivity towards the detected target species

Optimization of Cu-based catalyst for the electrocatalytic reduction of CO2 to fuels

In the last century, with the intensification of human industrial activities, carbon dioxide levels in the environment increased, making global warming and greenhouse effect pressing issues. In this sense, the electroreduction of CO2 is an interesting strategy, also if coupled with renewable energy sources to store the intermittent electric energy in form of chemical bonds [1]. Catalysts composed of a mixture of commercial copper nanoparticles (NPs) were studied. NPs with particles sizes of 25nm, 40-60nm and ZnO: 20-25 nm, named CZ 25_B and CZ_40-60_B. The molar ratio between copper and ZnO is equal to 65/35. Another commercial catalyst that was analysed because it is active for the CO2 hydrogenation is composed of CuO/ZnO/Al2O3 and traces of MgO (named CZA CC_B). These catalytic mixtures were prepared in a planetarian ball mill. Another sample was prepared by pre-oxidation of the Cu NPs and then by manual mixing with the ZnO (called CZ calc 2h). Carbon Nanotubes (CNT) was used as carbon substrate to increase the conductivity and allow a better catalytic ink dispersion. All the samples were characterized by BET analysis, FESEM microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical analysis. The electrocatalytic activity was tested by using a rotating disk electrode (RDE) at ambient conditions. The best conditions were appreciated at a potential equal to -2 V vs Ag/AgCl, with the lowest FE for H2 and the highest current density (mA/cm2) in absolute value. In Figure 1, the FE % of gaseous and liquid products are reported for the different prepared catalysts. From all test, the best catalytic activity with the lowest FEH2 was obtained with the Cu/ZnO peroxidised material (CZ calc 2h) at -2 V vs Ag/AgCl. In conclusion, it can be said that Cu-based catalysts were confirmed to be active towards CO2RR via the electrochemical method, with the advantage of performing the reactions at ambient conditions

Development of Cu-based hybrid catalysts for the electrocatalytic CO2 reduction to added value products

The simultaneous need to reduce greenhouse gas emissions and increase our energy supply makes the electrochemical reduction of CO2 a very attractive alternative [1]. In this context, science seeks effective methods to transform CO2 into chemicals of economic value. Among the possible products to obtain, we are especially interested in species with one or more carbon-carbon bonds, these types of compounds are favoured using copper as catalyst. Six catalysts were synthesized with different ratios of Cu, Zn Al and subsequently exposed to a thermal treatment to obtain the correspondent oxidized compounds. These kinds of catalyst are traditionally used in thermocatalysis for the efficient production of methanol at high temperature and pressure conditions [2]. Noting the good performance of this catalyst in thermocatalysis, it was chosen to carry out the experiment in the electrochemical reduction of CO2 at ambient conditions. Electrochemical tests were carried out in the rotating disk electrode (RDE) in order to reduce the mass transfer limitations that may exist due to the low solubility of CO2 in an aqueous medium. The chemical-physical properties of the catalyst were studied by several characterization techniques (e.g. XRD, XPS, BET, among others) to understand the role of the modification of the catalyst components during operation in the final selectivity and activity. Among the liquid products obtained are acetone, ethanol, isopropanol, formic acid and in some cases, methanol was also found. Moreover, gaseous products obtained were hydrogen, carbon monoxide and methane, being these last - gaseous products - those that present the highest faradaic efficiencies. These results were compared with the performance of the catalysts in a Gas Diffusion Electrode (GDE) cell, to obtain commercially-relevant current densities

The Effect of Sulfur and Nitrogen Doping on the Oxygen Reduction Performance of Graphene/Iron Oxide Electrocatalysts Prepared by Using Microwave-Assisted Synthesis

The synthesis of novel catalysts for the oxygen reduction reaction, by means of a fast one-pot microwave-assisted procedure, is reported herein and deeply explained. In particular, the important role of doping atoms, like sulfur and nitrogen, in Fe2O3-reduced graphene oxide nanocomposites is described to address the modification of catalytic performance. The presence of dopants is confirmed by X-ray Photoelectron Spectroscopy analysis, while the integration of iron oxide nanoparticles, by means of decoration of the graphene structure, is corroborated by electron microscopy, which also confirms that there is no damage to the graphene sheets induced by the synthesis procedure. The electrochemical characterizations put in evidence the synergistic catalysis effects of dopant atoms with Fe2O3 and, in particular, the importance of sulfur introduction into the graphene lattice. Catalytic performance of as-prepared materials toward oxygen reduction shows values close to the Pt/C reference material, commonly used for fuel cell and metal-air battery applications

Enhanced electrochemical oxidation of phenol over manganese oxides under mild wet air oxidation conditions

Low-cost manganese oxide, MnOx-based electrocatalysts, containing a-MnO2 and mixed a-Mn2O3/a- MnO2 phases, were synthesized by scalable anodic and cathodic electrodeposition methods, respectively. Their morphological and chemical composition were characterized by means of Field Emission Scanning Electronic Microscopy (FESEM), X-Ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). These electrodes were tested for the electro-oxidation of a recalcitrant molecule (i.e. phenol) in a lab- scale high temperature and high pressure (HTHP) batch electrocatalytic reactor. Their electrocatalytic activity was compared with that of state-of-the-art anodes for phenol electro-oxidation: antimony- doped tin oxide (SnO2eSb5þ) and ruthenium oxide (RuO2): first, under standard ambient conditions, and then, under the conditions of a Polymeric Electrolyte Membrane (PEM) electrolyzer (i.e. 85 C and 30 bar) and of mild Catalytic Wet Air Oxidation (CWAO, i.e. 150 C and 30 bar). Both reaction time and current density were varied to investigate their effect in the performances of the system as well as on the re- action mechanism. Both MnOx electrodes reported enhanced conversion efficiencies, up to ~75%, at the highest pressure and temperature, and at the lowest applied current density, which influenced the process by improving dissolution of the O2 evolved, the reaction kinetics and thermodynamics, and by minimizing irreversibilities, respectively. The here reported MnOx films achieved conversion and mineralization efficiencies comparable to Sb-SnO2 (that is the more toxic) and RuO2 (that is more expensive) materials, operating under mild CWAO operation conditions, which demonstrate the po- tential of the electrocatalytic HTHP process as a sustainable advanced oxidation technology for waste- water treatment or electrosynthesis applications

N-doped sponge-like biochar: a promising CO2 sorbent for CO₂/CH₄ and CO2/N₂ gas separation

Sponge-like biochar sorbents were prepared from the dissolution of chitosan followed by freeze-drying methodology and pyrolysis at three different temperatures (400, 600, and 800 °C) to produce sustainable N-enriched carbon materials with enhanced CO2 uptake from CO2/CH4 and CO2/N2 gas mixtures. The pyrolysis process was reproduced by operando TGA-IR to study the gas evolved from the pyrolysis process. It was found that the pyrolysis temperature highly influences the textural properties of the chitosan sponge-like biochar materials, impacting mainly the amount and type of the N-species on the sample but also at the microporosity. XPS revealed the transformation of the amino groups from chitosan into pyridinic-N, pyrrolic-N, graphitic center-N, and graphitic valley-N or pyridine-N oxide species during the pyrolysis process. Increasing the pyrolysis temperature enhanced the quantity of the latter two N-type species. All sponge-like biochars adsorbed higher amounts of CO2 compared with CH4 and N2 gases, with maximum CO2 uptake (∼1.6 mmol⋅g−1) at 100 kPa and 25 °C for the sample pyrolyzed at 600 °C (named CTO_P600). Biochar produced at 800 °C showed no longer adsorption capacity for CH4 and N2, having the highest selectivity value for CO2/N2 separation under continuous flux conditions among all prepared biochar sorbents. Isobaric CO2 adsorption measurements on the CTO_P600 sorbent revealed that physisorption phenomena predominantly governed the CO2 adsorption process, which was confirmed by its consistent adsorption capacity after 10 consecutive adsorption–desorption cycles. Moreover, the biochar exhibited tolerance to water vapor adsorption, indicating its suitability to work under moisture-rich conditions.publishe

Unveiling the power of titanium dioxide for energy storage and electrochemical technologies

Titanium dioxide nanotubes (TiO2 NTs) have been widely investigated in the past 20 years due to a variety of possible applications of this material. Indeed, their high surface area and tunable morphology can easily implement key features of TiO2, such as its biocompatibility and photo- and electrocatalytic properties. This combination makes TiO2 NTs perfect candidates for multifunctional applications ranging from biomedical application to sensing and energy devices. Herein, we present TiO2 NTs grown by anodic oxidation on top of a titanium foil in an ethylene glycol-based electrolyte with NH4F. The as-grown amorphous nanotubes were then subjected to annealing in a reducing atmosphere at different temperatures while maintaining their amorphicity. The morphological, physicochemical, and electronic properties were then thoroughly evaluated to assess their use in different fields, from energy storage devices to photo-catalytical applications

Optimization of BiVO4 photoelectrodes made by electrodeposition for sun-driven water oxidation

In this work, the synthesis of cheap BiVO4 photoanodes for the photoelectrochemical water splitting reaction was optimized via the scalable thin film electrodeposition method. Factors affecting the photoelectrochemical activity, such as the electrodeposition time, the ratio of the Bi-KI to benzoquinone-EtOH in the deposition bath, and the calcination temperature, have been investigated by using the Central Composite Design of Experiments. Pristine monoclinic scheelite BiVO4 photoanodes having a photocurrent density of 0.45 ± 0.05mA/cm2 at 1.23 V vs RHE have been obtained. It was shown that a high photocurrent density is generally dictated by the following physico-chemical properties: a higher crystallite size, optimal thickness and a porous morphology, which give rise to a low charge transfer resistance, low onset potential and a high donor density. Moreover, to the best of our knowledge, this is the first report on the depth profile XPS analysis performed in BiVO4 photoanodes made by electrodeposition technique, from which it was concluded that the surface V species exist as V4+ while the bulk V species are V5+. The V4+ induces a higher amount of surface oxygen vacancies, which was found to be beneficial for the photoactivity

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