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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. published

The direct hydrogenation of CO2 into dimethyl-ether (DME) has been studied in the presence of ferrierite-based CuZnZr hybrid catalysts. The samples were synthetized with three different techniques and two oxides/zeolite mass ratios. All the samples (calcined and spent) were properly characterized with different physico-chemical techniques for determining the textural and morphological nature of the catalytic surface. The experimental campaign was carried out in a fixed bed reactor at 2.5 MPa and stoichiometric H2/CO2 molar ratio, by varying both the reaction temperature (200–300 °C) and the spatial velocity (6.7–20.0 NL∙gcat−1∙h−1). Activity tests evidenced a superior activity of catalysts at a higher oxides/zeolite weight ratio, with a maximum DME yield as high as 4.5% (58.9 mgDME∙gcat−1∙h−1) exhibited by the sample prepared by gel-oxalate coprecipitation. At lower oxide/zeolite mass ratios, the catalysts prepared by impregnation and coprecipitation exhibited comparable DME productivity, whereas the physically mixed sample showed a high activity in CO2 hydrogenation but a low selectivity toward methanol and DME, ascribed to a minor synergy between the metal-oxide sites and the acid sites of the zeolite. Durability tests highlighted a progressive loss in activity with time on stream, mainly associated to the detrimental modifications under the adopted experimental conditions.

This study presents the immobilization with aldehyde groups (glyoxyl carbon felt) of alcohol dehydrogenase (ADH) and formate dehydrogenase (FDH) on carbon-felt-based electrodes. The compatibility of the immobilization method with the electrochemical application was studied with the ADH bioelectrode. The electrochemical regeneration process of nicotinamide adenine dinucleotide in its oxidized form (NAD

This work aims at providing a simple and effective method to optimize and improve the nitrogen-based defects into intrinsically N-doped carbon-based electrospun nanofibers (CNFs) for achieving highly active catalysts for the oxygen reduction reaction (ORR). To reach this goal, plasma treatments are investigated as an effective method to tune the distribution of the N-doping sites that are vital to improve the ORR catalytic activity of the material. Morphological, physical, chemical as well as electrochemical characterizations were performed on plasma-treated CNFs to demonstrate the effectiveness of such treatments to improve the catalytic behavior of CNFs toward ORR. Finally, Microbial Fuel Cells (MFCs) were selected to test the plasma-treated nanofibers as the cathode catalyst layer demonstrating an increase of the overall performance of the MFCs with respect to the devices using the Pt-based reference catalyst.

Self-assembled monolayers of 7-mercapto 4-methylcoumarin (MMC) on a flat gold surface were studied by Molecular Dynamics (MD) simulations, reference-free grazing incidence X-ray fluorescence (GIXRF) and X-ray photoemission spectroscopy (XPS), to determine the maximum monolayer density and to investigate the nature of the molecule/surface interface. In particular, the protonation state of the sulfur atom upon adsorption was analyzed, since some recent literature presented evidences for physisorbed thiols (preserving the S-H bond), unlike the common picture of chemisorbed thiyls (losing the hydrogen). MD with a specifically tailored force field was used to simulate either thiol or thiyl monolayers with increasing number of molecules, to determine the maximum dynamically stable densities. This result was refined by computing the monolayer chemical potential as a function of the density with the Bennet Acceptance Ratio method, based again on MD simulations. The monolayer density was measured with GIXRF, which provided a quantitative estimate of the number of sulfur atoms on top of flat gold surfaces embedded in a solution of MMC, to allow the formation of a dense monolayer. The sulfur core level binding energies in the same monolayers were measured by XPS, fitting the recorded spectra with the binding energies proposed in the literature for free or adsorbed thiols and thiyls, to get insight on the nature of the molecular species present in the layer.

Abstract High level of atmospheric carbon dioxide (CO2) concentration is considered one of the main causes of global warming. Electrochemical conversion of CO2 into valuable chemicals and fuels has promising potential to be implemented into practical and sustainable devices. In order to efficiently realize this strategy, one of the biggest efforts has been focused on the design of catalysts which are inexpensive, active and selective and can be produced through green and up-scalable routes. In this work, copper-based materials are simply synthesized via microwave-assisted process and carefully characterized by physical/chemical/electrochemical techniques. Nanoparticle with a cupric oxide (CuO) surface as well as various cuprous oxide (Cu2O) cubes with different sizes is obtained and used for the CO2 reduction reaction. It is observed that the Cu2O-derived electrodes show enhanced activity and carbon monoxide (CO) selectivity compared to the CuO-derived one. Among various Cu2O catalysts, the one with the smallest cubes leads to the best CO selectivity of the electrode, attributed to a higher electrochemically active surface area. Under applied potentials, all Cu2O cubes undergo structural and morphological modification, even though the cubic shape is retained. The nanoclusters formed during the material evolution offer abundant and active reaction sites, leading to the high performance of the Cu2O-derived electrodes. Graphic abstract

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 ± 0.05 mA/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.

The development of efficient catalysts is one of the main challenges in CO2 conversion to valuable chemicals and fuels. Herein, inspired by the knowledge of the thermocatalytic (TC) processes, Cu/ZnO and bare Cu catalysts enriched with Cu+1 were studied to convert CO2 via the electrocatalytic (EC) pathway. Integrating Cu with ZnO (a CO-generation catalyst) is a strategy explored in the EC CO2 reduction to reduce the kinetic barrier and enhance C–C coupling to obtain C2+ chemicals and energy carriers. Herein, ethanol was produced with the Cu/ZnO catalyst, reaching a productivity of about 5.27 mmol·gcat–1·h–1 in a liquid-phase configuration at ambient conditions. In contrast, bare copper preferentially produced C1 products like formate and methanol. During CO2 hydrogenation, a methanol selectivity close to 100% was achieved with the Cu/ZnO catalysts at 200 °C, a value that decreased at higher temperatures (i.e., 23% at 300 °C) because of thermodynamic limitations. The methanol productivity increased to approximately 1.4 mmol·gcat–1·h–1 at 300 °C. Ex situ characterizations after testing confirmed the potential of adding ZnO in Cu-based materials to stabilize the Cu1+/Cu0 interface at the electrocatalyst surface because of Zn and O enrichment by an amorphous zinc oxide matrix; while in the TC process, Cu0 and crystalline ZnO prevailed under CO2 hydrogenation conditions. It is envisioned that the lower *CO binding energy at the Cu0 catalyst surface in the TC process than in the Cu1+ present in the EC one leads to preferential CO and methanol production in the TC system. Instead, our EC results revealed that an optimum local CO production at the ZnO surface in tandem with a high amount of superficial Cu1+ + Cu0 species induces ethanol formation by ensuring an appropriate local amount of *CO intermediates and their further dimerization to generate C2+ products. Optimizing the ZnO loading on Cu is proposed to tune the catalyst surface properties and the formation of more reduced CO2 conversion products.

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-SnO2photo-electrocatalyst was synthesized and characterized. Coupling cuprous oxide with tin oxide allowed for protecting unstable Cu+1species from photo-corrosion. Evidence of the SnO2stabilization role were found via chronoamperometry tests under chopped light and XPS analysis. An optimized catalytic ink was developed to prepare the photocathodes. The CO2photo-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 H2evolution and promote ≥C1+products formation.

Self-assembled monolayers (SAM) of 7-mercapto-4-methylcoumarin (MMC) on a flat gold surface were studied by molecular dynamics (MD) simulations, reference-free grazing incidence X-ray fluorescence (GIXRF) and X-ray photoelectron spectroscopy (XPS), to determine the maximum monolayer density and to investigate the nature of the molecule/surface interface. In particular, the protonation state of the sulfur atom upon adsorption was analyzed, since some recent literature presented evidence for physisorbed thiols (preserving the S-H bond), unlike the common picture of chemisorbed thiyls (losing the hydrogen). MD with a specifically tailored force field was used to simulate either thiol or thiyl monolayers with increasing number of molecules, to determine the maximum dynamically stable densities. This result was refined by computing the monolayer chemical potential as a function of the density with the bennet acceptance ratio method, based again on MD simulations. The monolayer density was also measured with GIXRF, which provided the absolute quantification of the number of sulfur atoms in a dense self-assembled monolayer (SAM) on flat gold surfaces. The sulfur core level binding energies in the same monolayers were measured by XPS, fitting the recorded spectra with the binding energies proposed in the literature for free or adsorbed thiols and thiyls, to get insight on the nature of the molecular species present in the layer. The comparison of theoretical and experimental SAM densities, and the XPS analysis strongly support the picture of a monolayer formed by chemisorbed, dissociated thiyls.

Inspired by the knowledge of the thermocatalytic CO2 reduction process, novel nanocrystalline CuZnAl-oxide based catalysts with pyramidal mesoporous structures are here proposed for the CO2 electrochemical reduction under ambient conditions. The XPS analyses revealed that the co-presence of ZnO and Al2O3 into the Cu-based catalyst stabilize the CuO crystalline structure and introduce basic sites on the ternary as-synthesized catalyst. In contrast, the as-prepared CuZn- and Cu-based materials contain a higher amount of superficial Cu0 and Cu1+ species. The CuZnAl-catalyst exhibited enhanced catalytic performance for the CO and H2 production, reaching a Faradaic efficiency (FE) towards syngas of almost 95% at −0.89 V vs. RHE and a remarkable current density of up to 90 mA cm−2 for the CO2 reduction at −2.4 V vs. RHE. The physico-chemical characterizations confirmed that the pyramidal mesoporous structure of this material, which is constituted by a high pore volume and small CuO crystals, plays a fundamental role in its low diffusional mass-transfer resistance. The CO-productivity on the CuZnAl-catalyst increased at more negative applied potentials, leading to the production of syngas with a tunable H2/CO ratio (from 2 to 7), depending on the applied potential. These results pave the way to substitute state-of-the-art noble metals (e.g., Ag, Au) with this abundant and cost-effective catalyst to produce syngas. Moreover, the post-reaction analyses demonstrated the stabilization of Cu2O species, avoiding its complete reduction to Cu0 under the CO2 electroreduction conditions.

A simple, solvent-free and scalable route for the synthesis of nanostructured Bi5O7NO3 and Bi2O3 polymorphs photocatalysts and their heterostructures is here presented. Morphology, porosity and crystal phases were tuned by controlling the thermal decomposition of Bi(NO3)3:5H2O, by using different calcination temperatures and cooling processes. Bi5O7NO3 layered nanosheets, highly porous β-Bi2O3/Bi5O7NO3 heterostructured nanoflakes and micrometric sheets of α-Bi2O3 were obtained at temperatures of 400 °C, 425–450 °C and 525 °C with a slow cooling rate, respectively. Moreover, in contrast to previous reports on Bi5O7NO3, the role on the visible-light driven photocatalytic activity of Bi5O7NO3 due to the formation of a stable heterojunction with β-Bi2O3, which here was identified to be also formed by a rapid cooling after calcination at 400 °C, was deeply investigated and demonstrated. All the samples were fully characterized by X-ray Diffraction, Field-emission scanning electron microscopy, UV–vis spectroscopy, N2 adsorption and X-ray Photoelectron Spectrometry analyses. The role of oxygen vacancies, which indicate structural defects and/or sub-stoichiometric forms of Bi5O7NO3 or Bi2O3 in the photocatalysts surface, was also analyzed and correlated to their photo-response. Simulated sunlight-driven degradation of organic dyes with different functionalities, i.e. a cationic dye (Rhodamine B) and an anionic one (Indigo Carmine), was investigated and proved to be optimized due to an efficient synergy between suitable amounts of Bi5O7NO3 and β-Bi2O3 in the heterostructured samples. An improved charge carriers separation at the heterojunction interphase and an enhanced formation of reactive oxygen species in these materials were additionally confirmed by both photocatalytic water oxidation experiments with O2 evolution and mineralization of a refractory anionic dye, i.e. Remazol Brilliant Blue R. The latter was reached with an optimum photocatalyst/dye weight ratio of 33, which is about 2–3 times lower than previous literature results.

The need to reduce the costs of renewable energy sources such as (bio)electrochemical systems, has pushed the research towards alternative materials, especially for cathodes performing the oxygen reduction reaction, trying to maintain a catalytic efficiency close to that of platinum or platinum-based catalysts. In this work, at first, we present a manganese oxide-based catalyst in the form of xerogel, providing a complete description of the material. Later on, we present the comparison of two nanostructured manganese oxide-based catalysts, prepared from the same precursor, manganese acetate, but with different templating agents and with two different nanostructures: the xerogel previously discussed, and the nanofibers. With these two nanostructures, we prepared carbon-based electrodes, obtaining cathodes to be tested in microbial fuel cells. One of these cathodes performed very well and its performance was comparable to that of the reference which used Pt/C as catalyst.

Electrochemical Reduction of CO2 (ER-CO2) is a very attractive alternative to tackle Global Warming.[1] Cu-based materials have shown increased yields of hydrocarbon and oxygenate products, while its selectivity towards CO is low.[2] Inspired by the thermocatalytic process, a traditional co-precipitation method was employed to synthesize CuZnAl-based oxide catalysts with a mesoporous structure. This CuZnAl catalyst was tested for the first time for the ER-CO2 under ambient conditions. The Physico-chemical properties of the catalysts were studied by several characterization techniques (e.g., XRD, XPS, BET, SEM, TEM) and electrochemical impedance spectroscopy at different applied-potentials to understand the role of the modification of the catalyst components during operation in the final selectivity and activity. Results revealed that adding amphoteric metal oxides like ZnO and Al2O3 to the CuO-based catalyst contributed to promote CO formation over H2. XPS measurements on the fresh samples revealed that the ternary CuZnAl catalyst presented a lower percentage (5%) of Cu0 + Cu1+ mixture on the surface than the other catalysts, being mainly constituted by Cu+2. This material reached a Faradaic efficiency towards syngas of almost 95% at -0.89 V vs. RHE. Nevertheless, the highest production rate of syngas was obtained at the most negative applied potential (⁓ 17 μmol h-1 cm-2 at -1.14 V vs. RHE).). A tunable H2/CO ratio was achieved by applying different potentials, reaching lower values by increasing applied negative potential (CO current density increased). In fact, a syngas with a H2/CO ratio of ⁓ 2 was obtained at -0.89 V vs. RHE, which is a suitable raw material for further methanol synthesis. The enhanced performance for syngas production of the developed CuZnAl catalyst is demonstrated to be attributed to its surface properties (i.e., alkalinity and the oxidation state on the surface, its lowest diffusional mass transfer resistance, its highest total pore volume, and the lowest Cu crystals size among the prepared catalysts.

The electrocatalytic reduction of CO2 into useful fuels, exploiting rationally designed, inexpensive, active, and selective catalysts, produced through easy, quick, and scalable routes, represents a promising approach to face today’s climate challenges and energy crisis. This work presents a facile strategy for the preparation of doped SnO2 as an efficient electrocatalyst for the CO2 reduction reaction to formic acid and carbon monoxide. Zn or Ti doping was introduced into a mesoporous SnO2 matrix via wet impregnation and atomic layer deposition. It was found that doping of SnO2 generates an increased amount of oxygen vacancies, which are believed to contribute to the CO2 conversion efficiency, and among others, Zn wet impregnation resulted the most efficient process, as confirmed by X-ray photoelectron spectroscopy analysis. Electrochemical characterization and active surface area evaluation show an increase of availability of surface active sites. In particular, the introduction of Zn elemental doping results in enhanced performance for formic acid formation, in comparison to un-doped SnO2 and other doped SnO2 catalysts. At −0.99 V versus reversible hydrogen electrode, the total faradaic efficiency for CO2 conversion reaches 80%, while the partial current density is 10.3 mA cm−2. These represent a 10% and a threefold increases for faradaic efficiency and current density, respectively, with respect to the reference un-doped sample. The enhancement of these characteristics relates to the improved charge transfer and conductivity with respect to bare SnO2.

Transition-Edge Sensors (TESs) are versatile superconducting microcalorimeters used as single photon detectors in a large range of electromagnetic wavelength, from X-rays to near-infrared. Among the many materials investigated in literature, Ti/Au is one of the most widely used bilayer to fabricate TES thanks to simple deposition process, long term stability material and protection against oxidation of Ti film by Au over layer. Moreover, the critical temperature of Ti/Au can be tuned by trimming the thickness of Ti and Au films. For low energy photon detection, the Ti/Au superconducting layer performs simultaneously as absorber and thermometer. This implies that a TES thickness reduction helps to significantly reduce the thermal capacitance, which has a direct impact on the detector energy resolution. In this paper we present a study of the superconducting properties of Ti/Au films, grown in UHV by thermal evaporation as a function of Ti thickness. The chemical state of Ti and Ti/Au were analyzed by X-ray photoelectron spectroscopy, to evaluate the protective effect of Au film. The film morphology, structure and optical properties were investigated by ellipsometry. The critical temperature showed a marked trend on film thickness and was strongly affected by Au cover layer. Ti film of only 12 nm thick covered with 10 nm Au film showed a remarkable critical temperature of about 300 mK.

Novel electrocatalysts based on zinc oxide (ZnO) and biochars are prepared through a simple and scalable route and are proposed for the electrocatalytic reduction of CO₂ (CO₂RR). Materials with different weight ratios of ZnO to biochars, namely, pyrolyzed chitosan (CTO) and pyrolyzed brewed waste coffee (CBC), are synthesized and thoroughly characterized. The physicochemical properties of the materials are correlated with the CO₂RR to CO performance in a comprehensive study. Both the type and weight percentage of biochar significantly influence the catalytic performance of the composite. CTO, which has pyridinic- and pyridone-N species in its structure, outperforms CBC as a carbon matrix for ZnO particles, as evidenced by a higher CO selectivity and an enhanced current density at the ZnO_CTO electrode under the same conditions. The study on various ZnO to CTO weight ratios shows that the composite with 40.6 wt % of biochar shows the best performance, with the CO selectivity peaked at 85.8% at −1.1 V versus the reversible hydrogen electrode (RHE) and a CO partial current density of 75.6 mA cm–² at −1.3 V versus RHE. It also demonstrates good stability during the long-term CO₂ electrolysis, showing high retention in both CO selectivity and electrode activity.

Bimetallic copper-tin catalysts are considered cost-effective and suitable for large-scale electrochemical conversion of CO2 to valuable products. In this work, a class of tin (Sn) modified cuprous oxide (Cu2O) is simply synthesized through a one-pot microwave-assisted solvothermal method and thoroughly characterized by various techniques. Sn is uniformly distributed on the Cu2O crystals showing a cube-within-cube structure, and CuSn alloy phase emerges at high Sn contents. The atomic ratio of Cu to Sn is found to be crucially important for the selectivity of the CO2 reduction reaction, and a ratio of 11.6 leads to the optimal selectivity for CO. This electrode shows a high current density of 47.2 mA cm−2 for CO formation at −1.0 V vs. the reversible hydrogen electrode and also displays good CO selectivity of 80–90% in a wide potential range. In particular, considerable CO selectivity of 72–81% is achieved at relatively low overpotentials from 240 mV to 340 mV. During the long-term tests, satisfactory stability is observed for the optimal electrode in terms of both electrode activity and CO selectivity. The relatively low price, the fast and scalable synthesis, and the encouraging performance of the proposed material implies its good potential to be implemented in large-scale CO2 electrolyzers.

The electrocatalytic reduction of CO2 into useful fuels, exploiting rationally designed, inexpensive, active, and selective catalysts, produced through easy, quick, and scalable routes, represents a promising approach to face today’s climate challenges and energy crisis. This work presents a facile strategy for the preparation of doped SnO2 as an efficient electrocatalyst for the CO2 reduction reaction to formic acid and carbon monoxide. Zn or Ti doping was introduced into a mesoporous SnO2 matrix via wet impregnation and atomic layer deposition. It was found that doping of SnO2 generates an increased amount of oxygen vacancies, which are believed to contribute to the CO2 conversion efficiency, and among others, Zn wet impregnation resulted the most efficient process, as confirmed by X-ray photoelectron spectroscopy analysis. Electrochemical characterization and active surface area evaluation show an increase of availability of surface active sites. In particular, the introduction of Zn elemental doping results in enhanced performance for formic acid formation, in comparison to un-doped SnO2 and other doped SnO2 catalysts. At −0.99 V versus reversible hydrogen electrode, the total faradaic efficiency for CO2 conversion reaches 80%, while the partial current density is 10.3 mA cm−2. These represent a 10% and a threefold increases for faradaic efficiency and current density, respectively, with respect to the reference un-doped sample. The enhancement of these characteristics relates to the improved charge transfer and conductivity with respect to bare SnO2.

Bismuth vanadate (BiVO4) has surface states that give rise to defect levels that mediate electron-hole recombination. In order to minimize the inefficiencies, an ultrathin Al overlayer was deposited on the BiVO4electrodes. A 54 % improvement on the photocurrent density was obtained using the Al-modified BiVO4electrode, accompanied by a 15 % increase in stability over 7.5 h of continuous irradiation. Moreover, surface capacitance measurements showed that the Al overlayer was indeed passivating the surface states. We also shed light on the deposition of an Al overlayer on the surface of BiVO4, by investigating the process on model BiVO4powders. This study presents useful, previously unreported information about the surface chemistry of BiVO4based on experimental methods and gives unique insights on the characterization of the BiVO4surface. The existence of surface reactive sites on BiVO4was confirmed and quantified (1.5 reactive sites/nm2) via chemical titration

A catalyst plays a key role in the electrochemical reduction of CO2 to valuable chemicals and fuels. Hence, the development of efficient and inexpensive catalysts has attracted great interest from both the academic and industrial communities. In this work, low-cost catalysts coupling Cu and Zn are designed and prepared with a green microwave-assisted route. The Cu to Zn ratio in the catalysts can be easily tuned by adjusting the precursor solutions. The obtained Cu-Zn catalysts are mainly composed of polycrystalline Cu particles and monocrystalline ZnO nanoparticles. The electrodes with optimized Cu-Zn catalysts show enhanced CO production rates of approximately 200 μmol h-1 cm-2 with respect to those with a monometallic Cu or ZnO catalyst under the same applied potential. At the bimetallic electrodes, ZnO-derived active sites are selective for CO formation and highly conductive Cu favors electron transport in the catalyst layer as well as charge transfer at the electrode/electrolyte interface.

The light responsivity of ortho-nitrobenzyl esters (o-NBE) is exploited to inscribe µ-scale 2.5D patterns in thiol-ene networks by direct laser writing. For this purpose, a multifunctional thiol and a photosensitive alkene with an o-NBE chromophore are cured upon visible light exposure without inducing a premature photocleavage of the o-NBE links. Once the network is formed, a laser beam source with a wavelength of 375 nm is used for selectively inducing the photocleavage reaction of the o-NBE groups. Positive tone patterns are directly inscribed onto the sample surface without the requirement of a subsequent development step (removing soluble species in an appropriate organic solvent). Along with the realization of dry-developable micropatterns, the chemical surface composition of the exposed areas can be conveniently adjusted since different domains with a tailored content of carboxylic groups are obtained simply by modulating the laser energy dose. In a following step, those are activated and exploited as anchor points for attaching an Alexa-546 conjugated Protein A. Thus, the laser writable thiol-ene networks do not only provide a convenient method for the fabrication of positive tone patterns but also open future prospectives for a wide range of biosensing applications.

The performances of single chamber microbial fuel cells (SCMFCs) can be drastically enhanced by using nitrogen-doped electrospun carbon nanofibers (N–CNFs) as a surface coating material in composite anodes. The crucial step is the fine-tuning of the surface properties to improve bacteria growth on the anodic electrode. Two different pyrolysis treatments, conducted under inert atmosphere at 600 °C and 900 °C are analyzed in order to optimize the thermal treatment able to balance the surface chemistry of N–CNFs with respect to their electrical conductivity. N–CNFs treated at 600 °C result to be the best performing surface coating material in composite anodes, minimizing the process costs together while keeping excellent properties towards application. Morphological, physical and chemical features of the material are analyzed. The optimized N-doped CNFs show good interaction with microorganisms. All these features enhance the SCMFC performances. The SCMFCs with composite anode achieve power densities of 2.153 ± 0.011 W m−2, an order of magnitude higher than the results reached by using commercial carbon fibers. These performances are better than the ones obtained with activated CNFs proposed in the literature, where maximum pyrolysis temperature is up to 1100 °C and further chemical treatments are needed to ensure optimal surface chemistry, improving biofilm growth.

Eco-sustainable solutions for the neutralization of air and water pollutants have increasingly gravitated toward the use of heterogeneous photocatalysts. This approach, which transforms pollutants into harmless substances through a light-driven chemical reaction on a catalytic surface, must comply with eco-sustainability requirements and be easily applicable. Semiconductor-based photocatalysis is a promising pathway for the degradation of environmental pollutants and, among all the various semiconductors used, titanium dioxide has proved itself to be the foremost material for environmental remediation due to its highly desirable photocatalytic properties. Titanium dioxide, however, poorly exploits the visible part of the electromagnetic spectrum due to the relatively large band-gap of its anatase phase, and as such, the UV portion of the solar spectrum is largely responsible for its photocatalytic activity. Herein, we demonstrate a highly efficient visible light hybrid catalyst based on titanium dioxide and phenyl carbon nitride (PhCN). With the organic component providing a broad absorption up to 600 nm and fast charge exchange to the conduction band of TiO2, the combination allows for the highly efficient photocatalytic degradation of Rhodamine B under visible excitation.

A tin-modified copper foam for the efficient and selective reduction of CO2 to CO is reported. We employ a cost-efficient electrodeposition route to form a three-dimensional porous dendrite architecture, in which each dendrite possesses a copper core and a copper oxide/tin oxide shell. The sparse tin species on the electrode surface play a key role to achieve excellent faradaic efficiencies for CO formation with a maximum value of 94%. We demonstrate high CO partial current densities of 4.7 mA cm−2 and 7.9 mA cm−2 at applied potentials of -0.8 V and -1.1 V vs. the reversible hydrogen electrode, respectively. The high activity for electrochemical CO2 reduction is attributed to the unique hierarchical porous structure, which offers abundant electrochemically active sites and facilitates mass transport.

Innovative benzidine-free PANI-based inks for electrically conductive inkjet printed devices were developed and tested and the results compared with those obtained by traditional PANI. NMR investigations evidenced the presence of quinones and phenolic groups on the backbone of the innovative PANIs that are thought being responsible for the higher solubility in DMSO. A mechanism of reaction was proposed. The numerous characterizations (NMR, UV–Vis, FTIR, XPS and electrical investigations) allowed to compare protonation level, doping level, valence band maximum for both the type of PANI. The correlation among structural properties, printability, conductivity and solubility was discussed.

In this work we present a green approach to the synthesis of nitrogen-doped carbon-based aerogels with good conductivity and catalytic properties. With the aim to design an easily sustainable process, the starting precursors were selected among abundant waste-related organic materials. The naturally-derived polysaccharide agar worked as the carbon source in a water solution, while an amino acid, glycine or lysine has been used as the nitrogen source. By this synthesis approach, nitrogen defects were created into a 3D porous aerogel: they successfully acted as active catalytic sites for the reaction of oxygen reduction to water as demonstrated by electrochemical measurements. The best performing materials have been tested as cathodes in microbial fuel cells for 50 days, in conditions close to those the device could face in a real environment. The glycine derived carbon aerogels with the higher content of pyridinic nitrogen, as confirmed by several morphological characterizations, showed the best performance.

Carbon fibers (CF) were synthesized from waste clothes and treated with oxygen plasma at 100 W and 200 W for 5 min. Surface morphology and structure of the treated CF were studied via Field Emission Scanning Electron Microscopy (FESEM) and Raman spectroscopy. The functional groups on the surface of the plasma treated CF were studied through X-Ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared spectroscopy (FTIR). BET analysis showed that surface area of the fibers increases after treatment. The plasma treated CF retained higher amount of the epoxy resin in the wettability test. Composites were fabricated from untreated and treated CF in 1% and 3% by weight with epoxy resin. Mechanical and tribology behavior of the composites showed that the plasma treated CF composites are superior to their untreated counterparts. Morphology of the mechanical and the tribology specimen was studied with FESEM.

In this study, we report on the facile synthesis of a novel electrocatalysts for the oxygen reduction reaction (ORR), based on reduced graphene oxide (RGO), functionalized with metallic and non-metallic elements. In particular, thanks to a fast one-pot microwave-assisted procedure, we induced, in the RGO graphene lattice, a combined doping with nitrogen and sulphur, and the simultaneous decoration with antimony oxide nanocrystals. The multi-doped–decorated material shows enhanced catalytic performance towards ORR, with respect to common nitrogen- or sulphur-doped carbon-based materials. The presence of co-doping is confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy analysis. The detailed electrochemical characterization shows the simultaneous effects of dopant atoms on the catalytic behavior. In particular, the importance of nitrogen and sulphur atoms in driving the oxygen absorption, together with the role of antimony in enhancing the electrochemical performance toward the ORR, are discussed.

The Ti-48Al-2Cr-2Nb intermetallic alloy was coated by using a mixed titanium-aluminum nitride with the aim of improving its oxidation resistance. The protective TiAlN coatings were obtained by reactive High Power Impulse Magnetron Sputtering (HiPIMS) technique. The surface of the Ti-Al alloy was prepared for HiPIMS according to different methods; the deposition of an intermediate Ti-Al interlayer was also investigated. A cyclic oxidation test (100 and 200 cycles) was performed up to 950 °C in burner rig apparatus adopting severe heating and cooling rates. The microstructure and composition of samples before and after oxidation were investigated by several techniques: microscopy (optical and SEM-EDS), X-ray photoelectron spectrometry (XPS) and X-ray diffraction (XRD). The oxide layers formed on the sample surface showed different thickness and composition depending on the presence of the protective coating and the processing path adopted for its deposition. The nitride coatings appreciably enhanced the oxidation resistance and sustained repeated thermal shocks without showing damage or spallation.

Manganese oxides (MnxOy) are considered as a promising catalyst alternative to platinum in fuel cell applications. In fact, a proper catalyst is needed in order to facilitate the oxygen reduction reaction (ORR) at the cathode, and platinum is considered the best material due to its low overpotential for this reaction. Contrary to platinum, MnxOy is inexpensive, environmentally friendly and can be shaped into several nanostructures; furthermore, most of them show significant electro-catalytic performance. Several strategies have been carried out in order to increase their efficiency, by preparing light and high-surface area materials. In this framework, nanofibres are among the most promising nanostructures that can be used for this purpose. In this work, a study of the thermal, morphological and catalytic behavior of MnxOy nanofibres obtained through the electrospinning technique is proposed. Emphasis is given to the thermal evolution of the precursors, proposing a possible crystallization mechanism of the different manganese oxides obtained. It turns out that manganese oxide nanofibres exhibit good catalytic performance for the ORR, comparable to those obtained by using Pt-based catalysts.

A photolatent base ((1,5-diazabicyclo [4.3.0]non-5-ene) DBN) is used for the first time as photocatalyst for the curing of a formulation, which undergoes crosslinking by Michael addition reaction between acetoacetate and acrylate groups together with the reduction of graphene oxide. The reduction degree of graphene oxide during in situ irradiation is monitored by XPS analysis. The effect of the graphene oxide concentration on the photopolymerization reaction is studied by RT-FTIR. The thermal properties of the composite are determined by DSC analyses. The crosslinked nanocomposite showed a decrease of one order of magnitude for the electrical resistance in the presence of 3 wt% of graphene oxide. In addition, the thermal conductivity is significantly increased by the in situ reduction of graphene oxide in the organic matrix catalyzed by the phototriggered base.