Conversion Of Chemical Energy Research Articles

Simultaneous pollutant degradation and power generation in visible-light responsive photocatalytic fuel cell with an Ag-TiO2 loaded photoanode

Photocatalytic fuel cell (PFC) has been studied for treating phenolic organic pollutants and converting chemical energy into electricity effectively. The photoanode in the anode chamber degraded pollutants by photocatalytic oxidation, while the released electrons were transported to the cathode chamber via an external circuit to participate in the reduction reaction. These reactions enable the conversion of chemical energy into electrical energy. In this study, we firstly used sol–gel method to prepare Ag-TiO2 as the visible-light responsive catalyst. Then we compared two coating methods to obtain effective and stable photoanode with carbon foam as the support, i.e. sol–gel impregnation method and powder spray coating method. The 4-chlorophenol (4-CP), phenol and tetracycline (TC) were selected as the target pollutants. A dual chamber PFC was constructed to examine the pollutants degradation and power generation. The results showed that the photoanode prepared by powder spray coating method presented higher photoactivity and stability. The uniform and stable loading could be obtained when the loading ratio was 0.62 g/g. The degradation efficiency was maintained around 58% and the detachment of photocatalyst was 27.0% after three repeated cycles. In the PFC, the degradation efficiency of 4-CP, phenol and TC reached 32.6%, 37.9% and 96.4% in 6 h and the filling factors (FF) were 0.17, 0.31 and 0.44, respectively.

Reexamining the origin of the directionality of myosin V

The nature of the conversion of chemical energy to directional motion in myosin V is examined by careful simulations that include two complementary methods: direct Langevin Dynamics (LD) simulations with a scaled-down potential that provided a detailed time-resolved mechanism, and kinetic equations solution for the ensemble long-time propagation (based on information collected for segments of the landscape using LD simulations and experimental information). It is found that the directionality is due to the rate-limiting ADP release step rather than the potential energy of the lever arm angle. We show that the energy of the power stroke and the barriers involved in it are of minor consequence to the selectivity of forward over backward steps and instead suggest that the selective release of ADP from a postrigor myosin motor head promotes highly selective and processive myosin V. Our model is supported by different computational methods-LD simulations, Monte Carlo simulations, and kinetic equations solution-as well as by structure-based binding energy calculations.

Noble-Metal-Free Iron Phosphide Cocatalyst Loaded Graphitic Carbon Nitride as an Efficient and Robust Photocatalyst for Hydrogen Evolution under Visible Light Irradiation

Photocatalytic hydrogen (H2) evolution from water is a promising and sustainable approach for solar-to chemical energy conversion. However, the development of an efficient, robust, and low-cost visible-light-driven photocatalyst for H2 evolution is still one of the great challenges. Graphitic carbon nitride (g-C3N4) is an attractive candidate, but the activity of pristine g-C3N4 is largely limited. Herein, for the first time, we report the noble-metal-free iron phosphide cocatalyst decorated graphitic carbon nitride (g-C3N4/FexP) as a photocatalyst for the highly efficient and stable H2 evolution from water splitting irradiated by visible light. The peak H2 evolution rate of g-C3N4/FexP is ca. 277 times higher than that of pristine g-C3N4 and is almost comparable with the g-C3N4 modified by noble metal Pt cocatalyst. Additionally, g-C3N4/FexP demonstrates almost negligible photocatalytic degradation capability after five repeated cycles. Based on the detail analyses of photoluminescence and surface photov...

Engineering Shewanella oneidensis enables xylose-fed microbial fuel cell

BackgroundThe microbial fuel cell (MFC) is a green and sustainable technology for electricity energy harvest from biomass, in which exoelectrogens use metabolism and extracellular electron transfer pathways for the conversion of chemical energy into electricity. However, Shewanella oneidensis MR-1, one of the most well-known exoelectrogens, could not use xylose (a key pentose derived from hydrolysis of lignocellulosic biomass) for cell growth and power generation, which limited greatly its practical applications.ResultsHerein, to enable S. oneidensis to directly utilize xylose as the sole carbon source for bioelectricity production in MFCs, we used synthetic biology strategies to successfully construct four genetically engineered S. oneidensis (namely XE, GE, XS, and GS) by assembling one of the xylose transporters (from Candida intermedia and Clostridium acetobutylicum) with one of intracellular xylose metabolic pathways (the isomerase pathway from Escherichia coli and the oxidoreductase pathway from Scheffersomyces stipites), respectively. We found that among these engineered S. oneidensis strains, the strain GS (i.e. harbouring Gxf1 gene encoding the xylose facilitator from C. intermedi, and XYL1, XYL2, and XKS1 genes encoding the xylose oxidoreductase pathway from S. stipites) was able to generate the highest power density, enabling a maximum electricity power density of 2.1 ± 0.1 mW/m2.ConclusionTo the best of our knowledge, this was the first report on the rationally designed Shewanella that could use xylose as the sole carbon source and electron donor to produce electricity. The synthetic biology strategies developed in this study could be further extended to rationally engineer other exoelectrogens for lignocellulosic biomass utilization to generate electricity power.

Changes in SOFC Cathode Crystallographic Structure Induced by Oxygen Deficiency in Cathode Room

Stationary solid oxide fuel cell systems (SOFC) are highly efficient chemical energy conversion systems generating electricity and high quality heat. SOFC devices should be usable during over 40 000 hours and at least 100 thermal cycles. In this study, the changes of unit cell of cathode materials as a function of current density, p O2 and temperature were analyzed as a risk factor to increase the degradation rate of cathode electrode, during the cell working time. Reversible changes in the lattice parameters of SOFC cathode were observed depending on the temperature (T) and oxygen partial pressure (p O2) applied. The cathode potential, T and p O2 noticeably influences the unit cell volume, thus, the oxygen stoichiometry and concentration of vacancies. The electrode structure (porosity) has strong influence to the change kinetics of crystallographic parameters of cathode at in-situ element operating conditions. By polarizing the cathode electrode cathodically, the activity of electrode increase and the molecular oxygen concentration near the electrode surface decrease. Decrease of oxygen concentration in the porous cathode matrix causes the expansion of lattice parameter of cathode material. The electrode material (LSC and GSC) lose oxygen, Co4+ reduces to Co3+ and because of that unit cell expands. Only slight influence of oxygen partial pressure and potential to the crystallographic parameters of LSM (La0.6Sr0.4MnO3 − δ) was registered. At the same time for LSC (La0.6Sr0.4CoO3 − δ) and GSC (Gd0.85Sr0,15CoO3 − δ) the crystallographic unit cell volume was a function of electrode polarization as well as the oxygen partial pressure. There is no remarkable vacancy formation detectable with HT-XRD in LSM cathode lattice caused by electrode polarizations applied. Thermochemical crystallographic expansivity study of LSM, LSC and GSC cathodes with in-situ HT-XRD method gives valuable experimental data about the crystallographic changes caused by changes in operating parameters like cell potential, temperature, and oxygen partial pressure in cathode compartment and therefore helps to understand thermomechanical and degradation behavior as well as redox behavior of B site element (Co) as a function of different conditions applied for SOFC cathode. Figure 1. Selected segment from XRD pattern for LSCO and GSCO cathode at electrode potentials 0 and -0.9 V vs Pt/Pt/O2, respectively. Figure 1

Full‐Spectrum Solar‐Light‐Activated Photocatalysts for Light–Chemical Energy Conversion

AbstractThe realization of light–chemical energy conversion using solar light is an ideal goal in renewable energy studies. Many reports are concerned with extracting energy from solar light and the use/storage of the converted energy. Due to the progress in solar light absorption with various photocatalysts, the various energy conversion mechanisms using different photonic energies should be summarized. Therefore, the photocatalytic work that light can achieve with a certain photonic energy range, from UV light to visible light to near‐infrared light, is summarized in this review, including the most recent progress concerning light–chemical conversion mechanisms, classified as photocatalytic redox and photothermal catalysis. This review mostly concerns the mechanisms and specific strategies of light–chemical energy conversion based on various photonic energies.

Triplet versus singlet chemiexcitation mechanism in dioxetanone: a CASSCF/CASPT2 study

Chemiluminescence is a fundamental process of chemistry consisting in the conversion of chemical energy stored in chemical bonds into light. It is used by nature and by man-made technology, being especially relevant in chemical analysis. The understanding of the phenomenon strongly relies in the study of peroxide models such as 1,2-dioxetanones. In the present contribution, the singlet S 2 and the triplet T 2 potential energy surfaces of the unimolecular decomposition of 1,2-dioxetanone have been mapped along the O–O and C–C bond coordinates on the grounds of the multiconfigurational CASPT2//CASSCF approach. Results confirm the energy degeneracy between T 2, T 1, S 1, and S 0 at the TS region, whereas S 2 is unambiguously predicted at higher energies. Triplet-state population is also supported by the spin–orbit couplings between the singlet and triplet states partaking in the process. In particular, the first-principle calculations show that decomposition along the T 2 state is a competitive process, having a small (~3 kcal/mol) energy barrier from the ground-state TS structure. The present findings can explain the higher quantum yield of triplet-state population with respect to the excited singlet states recorded experimentally for the unimolecular decomposition of 1,2-dioxetanone models.

Energy Harvest from Contaminants via Coupled Redox Fuel Cells

Abstract Conversion of chemical energy from wastewater into electrical energy is receiving more and more attention. By selecting hydrogen-rich or nitrogen-containing pollutants as the fuels and oxidative contaminants as the oxidants, coupled redox fuel cells (CRFCs) were designed. Based on our previous work, we presented several typical fuel cells, namely the ethanol-Cr(VI), urea/urine-Cr(VI), NaBH 4 -Cu(II) and NH 3 -NO 3 − CRFCs. Converting chemical energy in fuels and oxidants directly into electricity and achieving simultaneous detoxification of pollutants are feasible via the CRFCs. These approaches are expected to become new options for retrieving energy from pollutants.

(Invited) Development of High Temperature Materials and Technologies for Electrochemical Storage and Conversion

The Advanced Research Projects Agency (ARPA-E) funds high risk, high reward transformational research to reduce energy related emissions, reduce imports of energy from foreign sources, improve energy efficiency across all economic sectors, and ensure US technological lead in advanced energy technologies, including electrochemical energy storage and transformation for grid scale and automotive applications. High temperature electrochemical technologies and supporting materials (membranes, current collectors, seals, etc.) play an important role in electrochemical (batteries with molten electrodes and molten salt electrolytes) and chemical (electrosynthesis of fuels) energy storage and energy conversion (intermediate and high temperature solid oxide and proton conducting fuel cells and electrolyzers). In addition, high temperature electrochemical technologies to process and recycle metals such as aluminum, titanium, and magnesium are important for advanced manufacturing. The use of high temperatures allows for utilization of ion conducting materials, electrolytes and electrocatalysts, which cannot be utilized at ambient conditions due to low conductivity or activity respectively. Current challenges in high temperature electrochemistry are increasing ionic conductivity of liquid and solid electrolytes to decrease working temperatures and expand material compatibility, improving activity and selectivity of electrocatalysts to decrease energy consumption and costs, increasing power density of stacks to decrease the capital costs, and optimizing the balance of system, which is extremely important for smaller scale devices. ARPA-E funded and currently funds multiple projects targeting high temperature electrochemical processes and development of materials compatible with these processes through OPEN, IDEAS and focused programs. The Modern Electro/Thermochemical Advances in Light Metals Systems (METALS) targets technologies that may provide inexpensive light metal materials for lightweight vehicles and aircraft. The Reliable Electricity Based on Electrochemical Systems (REBELS) program is focused at intermediate temperature fuel cells that operate between 200-500oC and includes cell capable to produce liquid fuels along with electricity to support the distributed energy generation for more reliable and flexible smart grid. The Renewable Electricity to Fuels through Utilization of Energy-dense Liquids (REFUEL) program seeks to fund the development of intermediate and high temperature electrosynthesis and fuel cells technologies to produce and utilize carbon-neutral fuels. This presentation will also highlight high temperature battery technologies using molten metal anodes funded by ARPA-E.

Robust Polyoxometalate/Nickel Foam Composite Electrodes for Sustained Electrochemical Oxygen Evolution at High pH.

The development of technologically viable electrodes for the electrochemical oxygen evolution reaction (OER) is a major bottleneck in chemical energy conversion. This article describes a facile one-step hydrothermal route to deposit microcrystals of a robust Dexter-Silverton polyoxometalate oxygen evolution catalyst, [Co6.8 Ni1.2 W12 O42 (OH)4 (H2 O)8 ], on a commercial nickel foam electrode. The electrode shows efficient and sustained electrochemical oxygen evolution at low overpotentials (360 mV at 10 mA cm-2 against RHE, Tafel slope 126 mV dec-1 , faradaic efficiency (96±5) %) in alkaline aqueous solution (pH 13). Post-catalytic analyses show no mechanical or chemical degradation and no physical detachment of the microcrystals. The results provide a blueprint for the stable "wiring" of POM catalysts to commercial metal foam substrates, thus giving access to technologically relevant composite OER electrodes.

High‐Performance Visible‐Light‐Driven Pt/CdS/Graphene Photoelectrocatalysts for Methanol Oxidation

AbstractFuel cells, as a technology for the conversion of chemical energy into electrical energy, have been recognized as a promising sustainable power source. Traditional electrocatalysts, together with optically active semiconductors, have been selected as promising catalysts for the improvement of anodic reactions. Herein, cadmium sulfide (CdS) nanoclusters decorated on reduced graphene oxide (RGO) nanosheets were obtained by using a one‐pot solvothermal method and then applied as photoactivated supports for the deposition of Pt nanoparticles. The ternary‐composite‐modified electrode displayed much higher catalytic properties for methanol oxidation than a binary Pt/CdS electrode. Interestingly, when the as‐prepared Pt/CdS/RGO electrode was irradiated with visible light, both the catalytic activity and the stability were improved greatly. The synergistic effect of RGO nanosheets and photoirradiation promoted electrocatalytic performance and stability. Our results provide new insight into the development of highly efficient photoelectrocatalysts for applications in direct methanol fuel cells in the presence of visible‐light illumination.

Hydrogen Through Water Electrolysis and Biomass Gasification for Application in Fuel Cells

Hydrogen is considered to be one of the most promising green energy carrier in the energy storage and conversion scenario. Although it is abundant on Earth in the form of compounds, its occurrence in free form is extremely low. Thus, it has to be produced by reforming processes, steam reforming (SR), partial oxidation (POX) and auto-thermal reforming (ATR) mainly from fossil fuels for high throughput with high energy requirements, pyrolysis of biomass and electrolysis. Electrolysis is brought about by passing electric current though two electrodes to evolve water into its constituent parts, viz. hydrogen and oxygen, respectively. Hydrogen produced by non-noble metal catalysts for both anode and cathode is therefore cost-effective and can be integrated into fuel cells for direct chemical energy conversion into electrical energy electricity, thus meeting the sustainable and renewable use with low carbon footprint.

List of Abstracts

. Production efficiency as well as the reduction of energy consumption and waste are the main drivers for the improvement of large-scale production in chemical industry. In addition, the demand for new processes – these days especially related to the chemical energy conversion as basis for the Energiewende – are additional triggers for innovation. Catalysis, well recognized by the public e.g. in form of the 3-way automobile catalyst, plays an important role for about 90% of all processes in chemical industry. The development of new and improved catalysts is a challenge for chemists – as is the search for new structural materials for mechanical engineers. Due to the often-necessary noble and thus expensive metals (e.g. palladium) in many catalysts, structural and chemical function have been developed separately in the two communities. Recent progress in catalytically active materials allows replacing expensive noble metals in selected catalytic processes by significant cheaper elements [1]. This offers the new perspective to combine structural and chemical functionality by innovative materials. Within this area, intermetallic compounds with their peculiar combination of crystal and electronic structure [2], represent an interesting class of materials to address this vision as will be shown in the contribution.

Heart failure drug changes the mechanoenzymology of the cardiac myosin powerstroke

Omecamtiv mecarbil (OM), a putative heart failure therapeutic, increases cardiac contractility. We hypothesize that it does this by changing the structural kinetics of the myosin powerstroke. We tested this directly by performing transient time-resolved FRET on a ventricular cardiac myosin biosensor. Our results demonstrate that OM stabilizes myosin's prepowerstroke structural state, supporting previous measurements showing that the drug shifts the equilibrium constant for myosin-catalyzed ATP hydrolysis toward the posthydrolysis biochemical state. OM slowed the actin-induced powerstroke, despite a twofold increase in the rate constant for actin-activated phosphate release, the biochemical step in myosin's ATPase cycle associated with force generation and the conversion of chemical energy into mechanical work. We conclude that OM alters the energetics of cardiac myosin's mechanical cycle, causing the powerstroke to occur after myosin weakly binds to actin and releases phosphate. We discuss the physiological implications for these changes.

COx-free hydrogen generation via decomposition of ammonia over copper and zinc-based catalysts

Production of hydrogen without any carbon dioxide or monoxide is of utmost importance for the chemical energy storage and conversion in a future low-carbon economy. Alumina-supported copper and Cu/Zn/Al2O3 catalysts were prepared by incipient wetness- and ultrasonic impregnation, while Zn/Al2O3 catalysts were also prepared to compare the effect of Zn. The characterisation of catalysts was carried out by N2 physisorption, XRD, H2-TPR, N2O chemisorption, NH3-TPD, CO2-TPD, H2-TPD, XPS and TEM. Catalysts prepared via ultrasonic impregnation showed a high metal dispersion and a small crystallite size, whereas Lewis acidic and basic sites were predominant on all catalysts, while the acid–base strength was strongly influenced by the presence of zinc in the case of Cu/Zn/Al2O3 catalysts. A high catalytic activity, reflected through the almost total conversion of ammonia at 600°C with the H2 production rate of 36.2mmolg−1min−1, was achieved over Cu/Zn/Al2O3 catalyst, prepared by ultrasonic impregnation. The dispersion of metal and its acidic or basic nature played an important role, even more so than the presence of the two or three potentially synergistic metals on the surface of a catalyst. Under the applied reaction conditions, the catalysts showed an excellent stability for more than 100h.

Mechanisms Underlying the Nucleation and Kinesin-Driven Assembly of Microtubule Rings

Active self-assembly processes rely on the conversion of chemical energy into mechanical work to overcome the limitations associated with diffusion-driven, passive self-assembly. For example, the transport of biotinylated microtubule filaments by surface-adsorbed kinesin motor proteins results in the actively assembly of bundles, rings, and spools in the presence of streptavidin. Observing the nucleation and assembly of these structures has been hindered by issues including controlled buffer exchange and photo-oxidative damage from fluorescent excitation. To address these issues, we developed a custom PDMS microfluidic device to characterize the earliest events involved in active assembly of microtubule rings and spools. Three distinct nucleation mechanisms were observed: pinning, collisions, and induced curvature. Pinning occurred when the leading tip of a microtubule encounters and stalls at an inactive motor. Experiments and numerical energy minimizations suggest that the diameter of ring/spools formed by pinning is strongly dependent on the surface density of kinesin motors. Collision-induced nucleation occurred when three (or more) microtubules simultaneous collide, forming a closed triangle that further evolved into a ring/spool. Collision accounted for the majority of nucleation events when photodamage was mitigated with our microfluidic device. The third nucleation mechanism, induced-curvature, was only observed at long-time scale, and attributed to a frozen-in curvature due to the binding of streptavidin-coated quantum dots to microtubules. We further showed that nucleation mechanisms affected both the diameter and rotation direction of the assembled rings/spools. Collectively, our studies provide fundamental insights on active assembly processes, which may be applied for regulating the morphology and functional properties of the resulting structures.Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Turning up the heat against metabolic syndrome and non-alcoholic fatty liver disease.

Brown adipose tissue (BAT), an organ specialized in the conversion of chemical energy from nutrients into heat through a process denominated as nonshivering thermogenesis, plays an important role in defence of body weight and homoeothermy in mammals. BAT nonshivering thermogenesis relies on the activity of the uncoupling protein 1 (UCP-1), a mitochondrial protein that, on demand, deviates proton gradient from ATP synthesis to heat generation. Energetically, this process is supported by BAT-elevated mitochondrial density and outstanding capacity to oxidize fatty acids and glucose. These unique features place BAT as an important determinant of whole-body energy, lipid and glucose homoeostases. In the present issue of Clinical Science, Poekes et al. have gathered supporting evidence indicating that, along with hyperphagia, impaired BAT diet-induced thermogenesis is an important factor driving the exacerbated diet-induced obesity, glucose intolerance and hepatic steatosis featured by foz/foz, a mouse strain that carries mutations in Alström syndrome protein 1 (ALMS1) gene mimicking human Alström syndrome. They also show that restoration of BAT nonshivering thermogenesis by intermittent cold exposure attenuated foz/foz mice obesity, glucose intolerance and liver steatosis. Altogether, these findings highlight the important contribution of BAT nonshivering thermogenesis to whole-body energy expenditure, lipid and glucose homoeostases and further support its potential utilization as a therapeutic strategy to treat metabolic diseases.

Methanol Synthesis from Industrial CO2 Sources: A Contribution to Chemical Energy Conversion

CO2 hydrogenation as a route for the chemical energy storage over a commercial Cu/ZnO/Al2O3 catalyst has been studied. To check the optimal conditions for an efficient methanol production the influence of temperature and space velocity on the catalytic performance has been demonstrated. Time-on-stream measurements in the absence and the presence of benzene in the gas feed mixture were performed to investigate the possibility to use alternative carbon sources, which contain traces of aromatics. The catalyst can operate in a stable way without the presence of carbon monoxide in the feed, which means that increased water contents in the product gas cannot destroy the catalyst’s performance completely. The presence of benzene in the feed does not lead to a deactivation of the catalyst. With these findings methanol production starting from exhaust gases from steel mills seems to become an interesting alternative for sustainable methanol production.Graphical

Light-harvesting synthetic nano- and micromotors: a review.

Nano- and micromotors are machines that can be made to perform specialized tasks as they propel themselves in response to certain stimuli. While the design of these self-propelling nano- and micromotors remains challenging, they have nevertheless attracted considerable research due to their many promising applications. Most self-propelled nano- and micromotors are based on the conversion of chemical energy into mechanical movement. Recently, however, the development of motors that can be propelled by light as an external stimulus has received much attention. The reason being that light is a renewable energy source that does not require any physical connection to the motor, does not usually lead to any waste products, and is easy to control. This review highlights recent progress in the development of light-harvesting synthetic motors that can be efficiently propelled and accurately controlled by exposure to light, and gives an overview of their fabrication methods, propulsion mechanisms, and practical applications.

Phytotechnological purification of water and bio energy utilization of plant biomass

The aim of the study was to explore the possibility of using the phytomass of aquatic plants as the substrate in the microbial fuel cells and selection of microorganisms suitable for the generation of electricity on this substrate. The conversion of chemical energy of phytomass of aquatic plants to the electrical energy was carried out in a microbial fuel cells by biochemical transformation. As biological agents in the generation of electricity in the microbial fuel cells was used commercial microbial drugs “Doctor Robic 109K” and “Vostok-EM-1”. The results of evaluation of the characteristics of electrogenic (amperage, voltage) and the dynamics of the growth of microorganisms in the microbial fuel cells presents in the experimental part. As a source of electrogenic microorganisms is possible to use drugs “Dr. Robic 109K” and “Vostok-EM-1” was established. The possibility of utilization of excess phytomass of aquatic plants, formed during the implementation of phytotechnological purification of water, in microbial fuel cells, was demonstrated. The principal possibility of creating hybrid phytotechnology (plant-microbe cells), allowing to obtain electricity as a product, which can be used to ensure the operation of the pump equipment and the creation of a full cycle of resource-saving technologies for water treatment, was reviewed.