Development of innovative materials used in electrochemical devices for the renewable production of hydrogen and electricity

One of the most important challenges for our society is providing powerful devices for renewable energy production. Many technologies based on renewable energy sources have been developed, which represent a clean energy sources that have a much lower environmental impact than conventional energy technologies. Nowadays, many researches focus their attention on the development of renewable energy from solar, water, organic matter and biomass, which represent abundant and renewable energy sources. This research is mainly focused on the development of promising electrode materials and their potential application on emerging technologies such as artificial photosynthesis and microbial fuel cell (MFC). According to desired proprieties of functional materials, this research was focused on two main materials: (1) TiO2 for the development of electrodes for the water splitting reaction due to its demonstrated application potential as photocatalyst material and (2) carbon-based materials for the development of electrodes for MFC. In the first part of the investigation, different TiO2 nanostructures have been studied including: synthesis, characterization and test of TiO2-based materials with the aim of improving the limiting factors of the photocatalytic reaction: charge recombination and separation/migration processes. The photo-catalytic properties of different TiO2 nanostructures were evaluated including: TiO2 nanoparticles (NPs) film, TiO2 nanotubes (NTs) and ZnO@TiO2 core-shell structures. Photo-electrochemical activity measurements and electrochemical impedance spectroscopy analysis showed an improvement in charge collection efficiency of 1D-nanostructures, related to a more efficient electron transport in the materials. The efficient application of both the TiO2 NTs and the ZnO@TiO2 core-shell photoanodes opens important perspectives, not only in the water splitting application field, but also for other photo-catalytic applications (e.g. photovoltaic cells, degradation of organic substances), due to their chemical stability, easiness of preparation and improved transport properties. Additionally, in order to improve the photo-catalytic activity of TiO2 NPs, PANI/TiO2 composite film was synthesized. PANI/TiO2 composite film was successfully applied as anode material for the PEC water splitting reaction showing a significant increase in the photocatalytic activity of TiO2 NPs composite film essentially attributed to the efficient separation of the generated electron and hole pairs. To date, no cost-effective materials system satisfies all of the technical requirements for practical hydrogen production under zero-bias conditions. For this propose, to promote the sustainability of the process, the bias require to conduct PEC water splitting reaction could be powered by MFC systems in which many efforts have been done to improve power and electricity generation as is explained below. In this work, different strategies were also applied in order to improve the performance of anode materials for MFCs. The investigation of commercial carbon-based materials demonstrated that these materials, normally used for other ends are suitable electrodes for MFC and their use could reduce MFC costs and improve the energy sustainability of the process. In addition, to enhance power generation in MFC by using low-cost and commercial carbon-based materials, nitric acid activation (C-HNO3) and PANI deposition (C-PANI) were performed on commercial carbon felt (C-FELT) in order to increase the performance of MFC. Electrochemical determinations performed in batch-mode MFC reveled a strong reduction of the activation losses contribution and an important decrease of the internal resistance of the cell using C-HNO3 and C-PANI of about 2.3 and 4.4 times, respectively, with respect to C-FELT. Additionally, with the aim of solvent different MFC operational problems such as: biofouling, low surface area and large-scale MFC, an innovative three-dimensional material effectively developed and used as anode electrode. The conductive carbon-coated Berl saddles (C-SADDLES) were successfully used as anode electrode in batch-mode MFC. Electrochemical results suggested that C-SADDLES offer a low-cost solution to satisfy either electrical or bioreactor requirements, increasing the reliability of the MFC processes, and seems to be a valid candidate for scaled-up systems and for continuous mode application of MFC technology. In addition, the electrochemical performance and continuous energy production of the most promising materials obtained during this work were evaluated under continuous operation MFC in a long-term evaluation test. Remarkable results were obtained for continuous MFCs systems operated with three different anode materials: C-FELT, C-PANI and C-SADDLES. From polarization curves, the maximum power generation was obtained using C-SADDLES (102 mW•m-2) with respect to C-FELT (93 mW•m-2) and C-PANI (65 mW•m-2) after three months of operation. The highest amount of electrical energy was produced by C-PANI (1803 J) with respect to C-FELT (1664 J) and C-SADDLES (1674 J). However, it is worth to note that PANI activity was reduced during time by the operating conditions inside the anode chamber. In order to demonstrate the wide application potential MFC, this work reports on merging heterogeneous contributions and combining the advantages from three separate fields in a system which enables the ultra-low-power monitoring of a microbial fuel cell voltage status and enables pressure monitoring features of the internal conditions of a cell. The solution is conceived to provide an efficient energy source, harvesting wastewater, integrating energy management and health monitoring capabilities to sensor nodes which are not connected to the energy grid. Finally, this work presented a general concept of the integration of both devices into a hybrid device by interfacing PEC and MFC devices (denoted as PEC-MFC), which is proposed to generate electricity and hydrogen using as external bias the potential produce by microbial fuel cel

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

A comparative study of the performance of commercial carbon felt and the innovative carbon-coated Berl saddles as anode electrode in MFC

Microbial Fuel Cell (MFC) is a prospective technology that allows oxidizing organic and inorganic matter to generate current by the activity of bacteria with a high potential as portable remote energy generation. To render MFC as a cost-effective and energy sustainable technology, low-cost conductive materials can be employed as support for bacterial growth and proliferation. For this reason, in this work we performed a comparative study of the performance between commercial carbon felt and the innovative carbon-coated Berl saddles (C-Berl saddles) developed in our labs used as anode electrode in MFC. Both the experiments were conducted simultaneously using the same MFC configuration in continuous mode for more than 3 months at room temperature (22 ± 2 °C). In the anodic chamber, a mixed microbial population naturally present in sea water was employed as active microorganisms and sodium acetate (1 g.L-1 per day) with buffer solution was continuously fed as substrate. In the cathodic chamber, carbon felt was used as electrode material and potassium ferricyanide with buffer solution as an electron acceptor. A complete characterization of anodic solution was carried out with continuous measurement of pH, conductivity and redox potential. Electrochemical characterization were performed as a follow: (i) polarization curves including: Linear Sweet Voltammetry, Current Interrupt and Electrochemical Impedance Spectroscopy using a multi-channel VSP potentiostat by BioLogic and (ii) current and voltage under an external resistance of 1000 Ω using a Data Acquisition Unit by Agilent 34972A. Results showed that C-Berl saddles performed better than carbon felt showing an average maximum power density of 90 mW.m-2 and 60 mW.m-2 , respectively. In addition, from current vs. time data both cells were produced a comparable quantity of energy, linked to the good biocompatibility, conductibility and high mechanical stretching of electrode materials. Furthermore, C-Berl saddles helped to reduce the biofouling and favored the growth of biofilm as anode material for scaling-up MFC

Streamlining of commercial Berl saddles: A new material to improve the performance of microbial fuel cells

Microbial fuel cell (MFC) is an upcoming technology that allows oxidizing organic matter to generate current by microorganism's activity. To render MFCs a cost-effective and energy sustainable technology, low-cost materials can be employed as support for bacteria growth and proliferation. With this purpose in mind, ceramic Berl saddles were opportunely covered by a thin and conductive carbon layer, thus obtaining an innovative low-cost anode material able to efficiently recover the electrons released by bacteria metabolisms. The conductive layer was obtained by using a-D-glucose deposition process within the following steps: impregnation, caramelization, and pyrolysis. In this way, a homogenous coating of polycrystalline graphitic carbon was successfully obtained and characterized by several methods. The carbon-coated Berl saddles were then tested as anode material in a two-compartment MFC prototype, in batch mode and using Saccharomyces cerevisiae as active microorganisms. The MFC performances were evaluated using electrochemical techniques. The carbon-coated Berl saddles showed a maximum power density of 130 mW m2 (29.6 mA L1) which is about 2e3 times higher than the values reported in literature by using commercial anode materials. In particular, we have carefully estimated the production and process costs of these carbon-coated Berl saddles used in our MFC prototype, obtaining a value comparable to the commercial carbon felt employed in the same MFC apparatus. All these results confirm that our innovative carbon-coated Berl saddles not only satisfy the electrical requirements, but also favor an optimal bacteria adhesion and can be produced as a low-cost anode for scaling-up MF

One Dimensional Core-Shell ZnO/TiO2 Nanowire Arrays for Visible Light Driven Photoelectrochemical Water Splitting

Photo-electrochemical (PEC) water-splitting offers a promising way for clean, low-cost and environmentally friendly production of H2 by solar energy. Wide-band-gap semiconductor materials such as zinc oxide (ZnO) and titanium dioxide (TiO2) have attracted considerable research interest in the past few decades as photocatalysts due to their unique properties: abundance, low cost and possibility to create nanostructures to improve their transport properties. In addition, ZnO nanowires (NWs) is one of the semiconductors with a high electronic mobility (1000 cm2Vs-1), which gives rise to fast electron transport and lower recombination of charge carriers. However, due to their large band gaps, they are active only under UV irradiation, and ZnO has the drawback of a low photo-corrosion resistance in aqueous media, that reduces their practical application. In this work, we present for the first time a fast and low-cost synthesis procedure for preparation of TiO2/ZnO core-shell heterostructures, in order to combine the merit of these two materials and improve their photocatalytic performances, with high efficiency and durability. In a first step, ZnO NWs were grown on glass electrodes covered with a Fluorine-doped Tin Oxide (FTO) conductive film by hydrothermal route. Subsequently, a shell of TiO2 nanoparticles was deposited in the ZnO NWs by in-situ sol-gel synthesis in a non-acidic solution. The resulting core-shell TiO2-ZnO structures were annealed in Air or N2 flow at 450oC and characterized by X-ray diffraction (Philips X’Pert, Cu Kα, λ = 1.54059 Å), Energy Dispersive Spectroscopy (EDS), Field Emission Scanning Electron Microscopy (FESEM, ZEISS Auriga) and Transmission Electron Microscopy (TEM, FEI Tecnai F20ST operating at 200 kV), clearly showing the formation of a crystalline anatase TiO2 shell completely covering the crystalline structures of wurtzite ZnO NWs, with a thickness dependent on the impregnation time in the titania synthesis bath. Moreover, optical properties and the surface properties of the TiO2/ZnO heterojunction have been further investigated by UV-Vis spectra and X-ray Photoelectron Spectroscopy (XPS), that evidence an increase of absorbance over the entire visible light region and a reduction of the band gap, with respect to the pristine ZnONWs treated under the same annealing conditions. PEC activity, action spectra and carriers dynamics of the samples were studied in NaOH (0.1M) electrolyte, using the prepared materials as working electrode, a Pt foil as counter electrode and a Ag/AgCl reference electrode, under dark and simulated solar light irradiation (using a 450W Xe lamp with a AM 1.5 filter) and employing monochromatic light in all the UV-Visible range

Optimization of 1D ZnO@TiO2Core–Shell Nanostructures for Enhanced Photoelectrochemical Water Splitting under Solar Light Illumination

A fast and low-cost sol-gel synthesis used to deposit a shell of TiO 2 anatase onto an array of vertically aligned ZnO nanowires (NWs) is reported in this paper. The influence of the annealing atmosphere (air or N 2) and of the NWs preannealing process, before TiO2 deposition, on both the physicochemical characteristics and photoelectrochemical (PEC) performance of the resulting heterostructure, was studied. The efficient application of the ZnO@TiO2 core-shells for the PEC water-splitting reaction, under simulated solar light illumination (AM 1.5G) solar light illumination in basic media, is here reported for the first time. This application has had a dual function: to enhance the photoactivity of pristine ZnO NWs and to increase the photodegradation stability, because of the protective role of the TiO2 shell. It was found that an air treatment induces a better charge separation and a lower carrier recombination, which in turn are responsible for an improvement in the PEC performance with respect to N2-treated core-shell materials. Finally, a photocurrent of 0.40 mA/cm2 at 1.23 V versus RHE (2.2 times with respect to the pristine ZnO NWs) was obtained. This achievement can be regarded as a valuable result, considering similar nanostructured electrodes reported in the literature for this application. © 2014 American Chemical Society

Fast and low-cost synthesis of 1D ZnO–TiO2 core–shell nanoarrays: Characterization and enhanced photo-electrochemical performance for water splitting

We report on a simple, fast and low-cost synthesis procedure for the complete covering of zinc oxide (ZnO) 1D nanostructures with a protective shell of titania (TiO2) nanoparticles. ZnO nanowires (NWs) were grown on transparent F-doped Tin Oxide (FTO) conductive layer on glass by seed layer-assisted hydrothermal route in aqueous media, while the titania shell was deposited on the ZnO NWs through an in situ non-acid sol–gel synthesis. The nanowires impregnation time in the titania sol was varied from 3 to 10 min. The resulting core–shell ZnO–TiO2 structures were characterized by different techniques, including Scanning and Transmission Electron Microscopy, X-ray diffraction and UV–Vis spectroscopy, confirming the uniform coverage of the wurzite ZnO NWs with anatase TiO2 nanoparticles (NPs), with a shell thickness dependent on the impregnation time in the titania synthesis bath. Photoelectrochemical (PEC) tests of the ZnO–TiO2 material, used as anode for the water splitting reaction, confirmed the formation of the heterojunction by the enhanced photocurrent densities, reaching values of about 0.7 mA/cm2 under simulated solar light (AM1.5G, 100mW/cm2). The core–shell photo-anodes performance was about twice and forty- times better than the ones with a film of equivalent thickness of bare ZnO NWs and TiO2 NPs, respectively. Steady-state measures of the photocurrent over the time and FESEM analysis confirmed that this procedure could be effectively used to both protect the nanostructured ZnO from photo-corrosion into different electrolytic media and enhance its photocatalytic properties

Oportunidad de emprendimiento con responsabilidad ambiental a partir de fibras sintéticas y pieles artificiales en el Ecuador

El (Censos, 2016) (INEC), en su encuesta nacional de empleo, desempleo y subempleo en el Ecuador, de marzo de 2016, informó que el 68,6% de las personas en edad de trabajar se considera económicamente activo; de éstos, el 94,3% se consideran con empleo, el 5,7% no cuenta con empleo formal o independiente. De las personas en edad de trabajar 31,4% forman parte de la población económicamente inactiva. El emprendimiento se presenta como una solución que permite generar empleo. A la luz de nuevas investigaciones sobre el consumo de carnes y productos procesados. Está evolucionando las percepciones de la población y se están modificando sus hábitos. Se cuestionan más sobre los efectos en su salud y sobre el impacto ambiental, es mayor la demanda de productos en cuya elaboración se genere un menor nivel de impacto ambiental.Siendo la responsabilidad ambiental, un factor que a las empresas competitivas globales y locales las ha llevado no sólo a cumplir con las disposiciones legales, sino a crear ventajas competitivas a partir de la promoción del trabajo realizado en favor de la protección del medio ambiente.El fomento de emprendimientos con responsabilidad ambiental, mediante el uso de fibras sintéticas y pieles artificiales ayudará a generar herramientas para incrementar el empleo, generando valor con responsabilidad ambiental.  Palabras clave: emprendimiento, responsabilidad ambiental, exportación, fibras artificiale

Oportunidad de emprendimiento con responsabilidad ambiental a partir de fibras sintácticas y pieles artificiales en el Ecuador

The (Census, 2016) (INEC), in its national survey of employment, unemployment and underemployment in Ecuador on march-2016, informed that 68,6% of people that have the age to work are considered economically active; of these ones, the 94,3% are employed, 5,7% don’t have formal employment o independent. From people that have the age to work, 31,4% belong to economically inactive population. Entrepreneurship is the solution that develops employment. Through new light investigations about the meat consumption and processed products. The perception of population is evolving and their habits are being modified. The effects on health and environmental impacts are questioned. It’s higher the demand of products which elaboration generates a lower environment impact. Being the environmental responsibility, a factor that competitive global and local companies has motivated them not only to obey legal dispositions, also to create competitive advantages through the job promotion realized to protect the natural environment. The phenomenon of ventures with environmental responsibility, through the use of synthetic fibers and artificial skins will help to generate tools to increase employment and develop value with social responsibility.El (Censos, 2016) (INEC), en su encuesta nacional de empleo, desempleo ysubempleo en el Ecuador, de marzo de 2016, informó que el 68,6% de las personas en edad detrabajar se considera económicamente activo; de éstos, el 94,3% se consideran con empleo, el5,7% no cuenta con empleo formal o independiente. De las personas en edad de trabajar 31,4%forman parte de la población económicamente inactiva. El emprendimiento se presenta como unasolución que permite generar empleo. A la luz de nuevas investigaciones sobre el consumo decarnes y productos procesados. Está evolucionando las percepciones de la población y se estánmodificando sus hábitos. Se cuestionan más sobre los efectos en su salud y sobre el impactoambiental, es mayor la demanda de productos en cuya elaboración se genere un menor nivel deimpacto ambiental. Siendo la responsabilidad ambiental, un factor que a las empresascompetitivas globales y locales las ha llevado no sólo a cumplir con las disposiciones legales,sino a crear ventajas competitivas a partir de la promoción del trabajo realizado en favor de laprotección del medio ambiente. El fomento de emprendimientos con responsabilidad ambiental,mediante el uso de fibras sintéticas y pieles artificiales ayudará a generar herramientas paraincrementar el empleo, generando valor con responsabilidad ambiental