Conversion Of Chemical Energy Research Articles

Thermochemical CO2 reduction over NiFe2O4@alumina filled reactor heated by high-flux solar simulator

This paper investigated CO2 utilization into energy density chemical using NiFe2O4@Alumina support porous-medium filled reactor heated by high-flux solar simulator. A combination of numerical and experimental studies is developed to investigate the synthesis and characterization of the redox materials, thermal characteristics, redox reaction kinetics, and redox performance of NiFe2O4@Alumina support porous oxide material. Moreover, thermal and chemical energy conversion efficiency of NiFe2O4@Alumina support was analyzed. Considering the difficulty related to designing and manufacturing porous-medium filled solar thermal receiver, this study could provide tremendous innovation values and pattern impacts in the field of solar thermochemical (STC) energy conversion into fuels and chemicals.

Water nano-diffusion through the Nafion fuel cell membrane

Nafion, an amphiphilic polymer based on fluorocarbon backbones and acid groups, is probably the most widely used fuel cell membranes. According to its hydration level it self-organizes leading to nano-cavities through which water diffuse. The diffusion of water that controls the protonic transport is then central in the conversion of chemical energy to the electrical one. Recently, a sub-diffusive and heterogeneous dynamics of water were experimentally evidenced paving the way for more efficient fuel cell membranes. Fundamentally, this dynamics which occurs at the nanoscale needs to be microscopically understood. Molecular dynamics simulations are thus performed to locally examine the water dynamics and its relation with the water and Nafion structure. The sub-diffusive regime is numerically corroborated and two sub-diffusive to diffusive transitions are found. The first is time dependent whereas the second is rather water uptake dependent. The sub-diffusive regime is ascribed to the water molecules strongly anchored close to the acid groups. We show that the sub-diffusive to diffusive time transition is the result of the elapsed time before to escape from the attractive interactions of the acid groups. The diffusive regime is recovered far from the acid groups in a homogeneous water phase that is the result of the percolation of the hydrogen bonding network. The progressive transition between sub-diffusive to diffusive regime as a function of the hydration level is due to the respective weight of diffusive dynamics that increases with respect to the sub-diffusive regime given the increase in diffusive pathways as the expense of the localized dynamics. Close to the fluorocarbon backbones the dynamics of water is also sub-diffusive but faster whereas time dynamical transition is not observed. Furthermore we highlight the existence of water corridors based on the hydrogen bonds between molecules forming single file structure in line with a sub-diffusive dynamics. These water corridors are thus possible conducting pathways of protons in a Grotthuss mechanism. Structurally we depict an interdigitated structure where the sulfonate are interleaved. Eventually, at high water uptake, we exhibit the self-organizing of Nafion leading to a phase separation between water and the Nafion membrane. We establish a specific interfacial organization of the hydrophilic sulfonate groups involving a water/Nafion interface.

Thermodynamic analysis of a thermal barrier-coated CI engine in a dual-fuel mode using biogas

Thermodynamic investigation of a diesel engine to assess its effectiveness in the conversion of chemical energy into useful work is necessary. In this work, the engine performance has been characterised based on the exergy and energy analysis and major sources of irreversibility in various engine processes are also studied in dual-fuel mode using biogas. Yttria-stabilised zirconia (YSZ) was used as a thermal barrier coating (TBC) on the piston crown and valves to boost the performance of the dual-fuel engine. The engine with TBC showed improved thermal and exergy efficiency with a reduction in exergy destruction. The brake thermal efficiency (BTE) was 24.12% and 25.62% for diesel-alone operation in uncoated and coated engine, respectively, at full-load operation, while the BTE decreased by 23%, 29% and 34% for the uncoated engine and 10%, 12% and 19% for the coated engine with the induction of biogas at 0.6, 0.8 and 1 kg h−1, respectively.

Design principles of solar light harvesting in plants: Functional architecture of the monomeric antenna CP29

In plants and green algae, light-harvesting complexes (LHCs) are a large family of chlorophyll binding proteins functioning as antennae, collecting solar photons and transferring the absorbed energy to the photosynthetic reaction centers, where light to chemical energy conversion begins. Although LHCs are all highly homologous in their structure and display a variety of common features, each complex finds a specific location and task in the energy transport. One example is CP29, which occupies a pivotal position in Photosystem II, bridging the peripheral antennae to the core. The design principles behind this specificity, however, are still unclear.Here, a synergetic approach combining steady-state and ultrafast spectroscopy, mutational analysis and structure-based exciton modeling allows uncovering the energy landscape of the chlorophylls bound to this complex. We found that, although displaying an overall highly conserved exciton structure very similar to that of other LHCs, CP29 possesses an additional terminal emitter domain. The simultaneous presence of two low energy sites facing the peripheral antennae and the core, allows CP29 to efficiently work as a conduit in the energy flux. Our results show that the LHCs share a common solid architecture but have finely tuned their structure to carry out specific functions.

Electricity Arbitration and Sector Coupling with an Experimentally Validated Reversible Solid Oxide Cell Reactor System Connected to the Natural Gas Grid

Chemical energy storage offers an attractive solution for the arbitration of intermittent renewable electricity due to its higher energy storage capacity and storage duration. Reversible solid oxide cell (rSOC) reactor systems can efficiently operate in electrolysis operation to convert electrical energy to chemical energy or in fuel cell mode to convert chemical energy back to electrical energy. Natural gas is widely used in the chemical industry as a source of energy and hydrogen. Hence, storing electrical energy in the form of synthetic natural gas can couple electricity arbitration with chemical process industries. A methane‐based rSOC system concept for the purpose of energy storage and sector coupling is investigated. A process system analysis is performed based on an experimental study of a commercially available rSOC reactor. A validated rSOC reactor model is used to identify optimal system operating conditions. The proposed system concept achieves a chemical to electrical energy conversion efficiency of 57% and electrical to chemical energy conversion efficiency of 93% based on first law and lower heating value. A net electrical storage efficiency of 53% can be achieved.

Control of surface structures and functionalities in perovskite-type ferroelectric oxides and their potential applications

Over the past decades, exploration and artificial control of the surface and interfacial structure of the materials have played an important role in chemical catalyzing, energy conversion, information storage and medical field, and thus the finding of suitable materials with controllable surface/interface properties has attracted intense interest in recent years. Perovskite-type ferroelectric oxides are considered to be one of the most promising functional materials due to their intrinsic, non-volatile, reversible spontaneous polarization and controllable polar surface with high charge density. The investigating of the interaction between polarization and surface structure of perovskite-type ferroelectric oxide is very important for understanding the surface (interface) energy conversion, regulating the adsorption and desorption on the surface, controlling interfacial chemical reaction, and designing stable low-power electronic devices. In this paper, we summarize the theoretical mechanism and potential applications of the surface structures and functionality in perovskite-type ferroelectric oxide from three aspects. Firstly, we describe the inseparable relationship between the stabilized ferroelectric phase and surface structure of ferroelectric material, and illustrate the formation mechanism of complex surface structure of perovskite-type ferroelectric oxide. In order to reduce the surface energy to stabilize the polar surface of the material, perovskite-type ferroelectric oxide always needs to absorb foreign charged particles, change the stoichiometry and conduct electron orbital hybridization or surface relaxation, etc., which will cause the complexity of the surface structure of ferroelectric. Secondly, we outline the influence of ferroelectric polarization on the surface structure of ferroelectric and the behavior of changing ferroelectric polarization by controlling surface structure through adjusting the external environment, which provides an important basis for the subsequent regulation of the surface performance and functionality of perovskite-type ferroelectric oxide. Finally, we introduce the utilization of the controllable physical and chemical properties of ferroelectric surface (interface) into large area and into nanoscale (nanodomain), which has bright application prospects in many frontier fields, including non-volatile memory system, cell proliferation, microfluidic control system, catalysis, optical device and photodetector and so on. Furthermore, considering the limitations of current scientific research about the ferroelectric surface, we put forward the prospects for the future development of the ferroelectric material in the areas of information storage, controllable chemical reactions and new energy conversion.

Comparison of microstructural evolution of fuel electrodes in solid oxide fuel cells and electrolysis cells

Solid oxide cells are electrochemical devices used for the conversion of chemical energy to electrical energy (Solid Oxide Fuel Cells-SOFC) and vice versa (Solid Oxide Electrolysis Cells-SOEC). However, long-term performance degradation impedes the widespread commercialization of the technology. To investigate the effects of operation mode on the degradation of Ni/yttria-stabilized zirconia (YSZ) electrodes, two cells from the same production batch are tested for 1000 h at 800 °C; one as SOFC and the other as SOEC. The cells are fed with the same gas composition at the fuel inlet side (p(H2O)/p(H2) = 0.5/0.5) while the direction of the current (±1 A cm−2) is reversed. It is found that Ni coarsening occurs to a similar extent in both operation modes while Ni depletion is only observed in SOEC mode, in the region close to the electrode/electrolyte interface. Here, the Ni/(Ni + Zr + Y) atomic ratio decreases from ~0.49 before operating the cell to ~ 0.28 and the SOEC shows a pronounced decrease in percolating triple phase boundaries (TPBs). The wettability of Ni on YSZ is studied and hypotheses are presented to correlate the phenomena of Ni coarsening and Ni depletion with the cell operation mode.

Efficient conversion of chemical energy into mechanical work by Hsp70 chaperones.

Hsp70 molecular chaperones are abundant ATP-dependent nanomachines that actively reshape non-native, misfolded proteins and assist a wide variety of essential cellular processes. Here, we combine complementary theoretical approaches to elucidate the structural and thermodynamic details of the chaperone-induced expansion of a substrate protein, with a particular emphasis on the critical role played by ATP hydrolysis. We first determine the conformational free-energy cost of the substrate expansion due to the binding of multiple chaperones using coarse-grained molecular simulations. We then exploit this result to implement a non-equilibrium rate model which estimates the degree of expansion as a function of the free energy provided by ATP hydrolysis. Our results are in quantitative agreement with recent single-molecule FRET experiments and highlight the stark non-equilibrium nature of the process, showing that Hsp70s are optimized to effectively convert chemical energy into mechanical work close to physiological conditions.

Molybdate pumping into the molybdenum storage protein via an ATP-powered piercing mechanism

The molybdenum storage protein (MoSto) deposits large amounts of molybdenum as polyoxomolybdate clusters in a heterohexameric (αβ)3 cage-like protein complex under ATP consumption. Here, we suggest a unique mechanism for the ATP-powered molybdate pumping process based on X-ray crystallography, cryoelectron microscopy, hydrogen-deuterium exchange mass spectrometry, and mutational studies of MoSto from Azotobacter vinelandii. First, we show that molybdate, ATP, and Mg2+ consecutively bind into the open ATP-binding groove of the β-subunit, which thereafter becomes tightly locked by fixing the previously disordered N-terminal arm of the α-subunit over the β-ATP. Next, we propose a nucleophilic attack of molybdate onto the γ-phosphate of β-ATP, analogous to the similar reaction of the structurally related UMP kinase. The formed instable phosphoric-molybdic anhydride becomes immediately hydrolyzed and, according to the current data, the released and accelerated molybdate is pressed through the cage wall, presumably by turning aside the Metβ149 side chain. A structural comparison between MoSto and UMP kinase provides valuable insight into how an enzyme is converted into a molecular machine during evolution. The postulated direct conversion of chemical energy into kinetic energy via an activating molybdate kinase and an exothermic pyrophosphatase reaction to overcome a proteinous barrier represents a novelty in ATP-fueled biochemistry, because normally, ATP hydrolysis initiates large-scale conformational changes to drive a distant process.

Doping Iron in CsPbBr3 Perovskite Nanocrystals for Efficient and Product Selective CO2 Reduction.

Lead halide perovskite nanocrystals have recently emerged as an efficient optical material for light harvesting. While these have been extensively studied for obtaining bright emissions, their use as catalysts for enhancing the rate of chemical reactions has been explored little. Considering their importance in catalysis, herein, Fe(II)-doped CsPbBr3 perovskite nanocrystals have been explored for photocatalytic reduction of CO2. In comparison to undoped CsPbBr3, doped nanocrystals showed enhanced catalytic activity and also predominantly led to evolution of CH4 instead of CO. The observation of a reverse trend of predominated CH4 evolution in doped nanocrystals rather than CO observed for undoped nanocrystals was correlated to the adsorption/desorption energy of respective products established theoretically earlier. This selective evolution of major products on doping remained unique and also a step forward for understanding more regarding light to chemical energy conversions using perovskite nanocrystals.

Investigación de Celdas de Combustible de Amoniaco Directo como fuente de Energía Alternativa. Desarrollo de Electrocatalizadores para las Reacciones de Electrodo en Medio Alcalino

Las reservas de combustibles fósiles se consumen en cantidades crecientes y existe actualmente una gran preocupación en los gobiernos centrales por el grado de contaminación ambiental alcanzado durante las últimas décadas a nivel mundial. Disponer de energía es una necesidad en la vida moderna y poseerla se convertirá, en los próximos años, en un bien de alto valor en las sociedades desarrolladas. Las celdas de combustible son dispositivos que permiten la conversión directa de la energía química contenida en ciertos compuestos como el hidrógeno, metanol, etanol, amoníaco, en energía eléctrica. Las celdas de combustible alcalinas (AFCs) presentan una eficiencia mucho mayor que las que operan en medio ácido. A diferencia del metanol, etanol y etilenglicol, el amoníaco es un compuesto libre de carbono, por lo que no presenta como producto de reacción CO2, esto hace a el amoníaco un combustible ideal para las celdas con cero emisiones. Muchos investigadores ya han denominado al amo níaco como el combustible del futuro. La producción de amoníaco emplea como materia prima N2 del aire e H2 mediante un proceso bien conocido, sencillo y de bajo costo, empleando esencialmente el proceso Haber-Bosch. En nuestro país, se produce un excedente de NH3 de 80.000 ton/año, que mayormente se exporta. Desde el 2005, se han incrementado significativamente las publicaciones científicas con estudios detallados de la oxidación de amoníaco en medio alcalino y recientemente se han reportado potencias picos de 72 mW cm-2utilizando una Celda de Combustible Alcalina de Amoníaco Directo (DAAFC). Esta propuesta de tesis pretende realizar aportes significativos en el área de energías alternativas y específicamente en el desarrollo de las DAAFCs. Se plantea como objetivo general desarrollar celdas alcalinas de amoniaco directo como una fuente de energía alternativa que trabaje a baja temperatura empleando membrana sólida intercambiadora de aniones. En resumen, los objetivos específicos serán: -Sintetizar y caracterizar física y electroquímicamente electrocatalizadores para la reacción de reducción de oxígeno (ORR). -Sintetizar y caracterizar física y electroquímicamente electrocatalizadores para la reacción de oxidación de amoníaco (AOR).-Desarrollar ensambles electrodo-membrana-electrodo (MEAs) con los catalizadores sintetizados en el laboratorio y evaluar física y electroquímicamente dichas MEAs. -Desarrollar un prototipo de Celda de Combustible Alcalina de Amoniaco Directo (DAAFC).

A hygroelectric power generator with energy self-storage

Devices that convert ambient energy into electricity and simultaneously store it for future usage are highly desirable. Herein, we have designed a hygroelectric power generator with energy self-storage ability (HPGES) by hybridizing a moist-electric energy harvester with a supercapacitor, thus achieving the conversion of chemical energy into electricity and the storage of electric energy at the same time. An array of ten HPGES devices are able to deliver a voltage output of 2 V and adequately drive a commercial calculator.

Direct Conversion of Chemical Energy into Electrical Energy in the Combustion of a Thin Three-Layer Charge

This paper presents a study of direct conversion of chemical energy into electrical energy during the combustion of a (80Zr + 20CuO)–(LiF + CaF2 + MgF2)–(15Zr + 85CuO) thin three-layer condensed energy system, which is a high-temperature galvanic cell. It is determined that this cell during combustion generates an electric signal with an amplitude of 1.6 V and a half-width of 15 s. Its formation mechanism is proposed. A time-resolving X-ray diffraction method is used to identify the phases formed.

Glucose oxidase bioelectrodes in devices implanted in living plants for energy applications.

The growth of the world population and the lack of energy supply have led to the development of technologies to obtain alternative energy that has a minimal environmental impact, as is the case of fuel cells. In this work, the development of electrodes using glucose oxidase enzyme immobilized with functionalized carbon nanofibers on graphite rods is proposed for its application in a fuel cell implanted in living plants, specifically in cacti. The purpose is to convert solar energy to chemical and then, to electric energy, carrying out the glucose oxidation contained in these plants. The use of a living plant as a fuel cell comes from the idea of taking advantage of more efficiently the conversion of chemical energy, which comes from the plant’s photosynthesis until is converted into electrical energy.

Characterization of Calcia Stabilized Zirconia as a solid E lectrolyte M ade through a sol gel M ethod in Solid Oxide Fuel Cell

Solid Oxide Fuel Cell (SOFC) is a solid-state energy conversion device which produces electricity through the conversion of chemical energy directly to electrical energy. The research was carried out to characterize Calcia Stabilized Zirconia (CSZ) that was made using sol gel method. In this study, the production of CSZ pellets consisted of three steps. First step was the extraction of ZOC (ZrOCl28H2O) and second step was the production of Zr(OH)4 and the last step was dissolution of ZrOH4 into HCl and then adding CaO to get CSZ powder. The CSZ powder was then pressed to form pellets, followed by sintering at 1200 oC for 3 hours. The characterization was conducted using X ray diffraction to analyze the presence of impurities as well as the formation of cubic phase and scanning electron microscope was used to observe the pores in the microstructure. From the XRD data and SEM analysis, it can be concluded that the Calcia Stabilized Zirconia as a solid electrolyte in SOFC using sol gel method gave promising results.

Photoactive Earth-Abundant Iron Pyrite Catalysts for Electrocatalytic Nitrogen Reduction Reaction.

The generation of ammonia, hydrogen production, and nitrogen purification are considered as energy intensive processes accompanied with large amounts of CO2 emission. An electrochemical method assisted by photoenergy is widely utilized for the chemical energy conversion. In this work, earth-abundant iron pyrite (FeS2 ) nanocrystals grown on carbon fiber paper (FeS2 /CFP) are found to be an electrochemical and photoactive catalyst for nitrogen reduction reaction under ambient temperature and pressure. The electrochemical results reveal that FeS2 /CFP achieves a high Faradaic efficiency (FE) of ≈14.14% and NH3 yield rate of ≈0.096 µg min-1 at -0.6 V versus RHE electrode in 0.25 m LiClO4 . During the electrochemical catalytic reaction, the crystal structure of FeS2 /CFP remains in the cubic pyrite phase, as analyzed by in situ X-ray diffraction measurements. With near-infrared laser irradiation (808 nm), the NH3 yield rate of the FeS2 /CFP catalyst can be slightly improved to 0.1 µg min-1 with high FE of 14.57%. Furthermore, density functional theory calculations demonstrate that the N2 molecule has strong chemical adsorption energy on the iron atom of FeS2 . Overall, iron pyrite-based materials have proven to be a potential electrocatalyst with photoactive behavior for ammonia production in practical applications.

Rotation and propulsion in 3D active chiral droplets

Chirality is a recurrent theme in the study of biological systems, in which active processes are driven by the internal conversion of chemical energy into work. Bacterial flagella, actomyosin filaments, and microtubule bundles are active systems that are also intrinsically chiral. Despite some exploratory attempt to capture the relations between chirality and motility, many features of intrinsically chiral systems still need to be explored and explained. To address this gap in knowledge, here we study the effects of internal active forces and torques on a 3-dimensional (3D) droplet of cholesteric liquid crystal (CLC) embedded in an isotropic liquid. We consider tangential anchoring of the liquid crystal director at the droplet surface. Contrary to what happens in nematics, where moderate extensile activity leads to droplet rotation, cholesteric active droplets exhibit more complex and variegated behaviors. We find that extensile force dipole activity stabilizes complex defect configurations, in which orbiting dynamics couples to thermodynamic chirality to propel screw-like droplet motion. Instead, dipolar torque activity may either tighten or unwind the cholesteric helix and if tuned, can power rotations with an oscillatory angular velocity of 0 mean.

Fe2O3/NiO photocathode for photocatalytic methanol fuel cell: An insight on solar energy conversion

A promising photocathode material based on Fe2O3/NiO heterostructure was developed for efficient photoelectric conversion in a methanol fuel cell. The Fe2O3/NiO heterogeneous film was prepared via in-situ hydrothermal synthesis and then cathodic electrodeposition process. Surface photovoltage results showed that after electrodeposition of NiO on the Fe2O3 film, the separation direction of photogenerated electrons and holes was reversed. The photogenerated electrons accumulated on the surface of Fe2O3/NiO photocathode can induce the oxygen reduce reaction due to the relatively high conduction band level of the entire semiconductor composite. In addition, the Fe2O3/NiO based photocatalytic methanol fuel cell showed significant improvements under illumination of simulated sunlight, and the short-circuit current and open-circuit voltage reach 183 μA/cm2 and 0.48 V respectively. The work provided a new vision for solar - chemical energy conversion in the fuel cell.

Synthetic Systems Powered by Biological Molecular Motors

Biological molecular motors (or biomolecular motors for short) are nature's solution to the efficient conversion of chemical energy to mechanical movement. In biological systems, these fascinating molecules are responsible for movement of molecules, organelles, cells, and whole animals. In engineered systems, these motors can potentially be used to power actuators and engines, shuttle cargo to sensors, and enable new computing paradigms. Here, we review the progress in the past decade in the integration of biomolecular motors into hybrid nanosystems. After briefly introducing the motor proteins kinesin and myosin and their associated cytoskeletal filaments, we review recent work aiming for the integration of these biomolecular motors into actuators, sensors, and computing devices. In some systems, the creation of mechanical work and the processing of information become intertwined at the molecular scale, creating a fascinating type of "active matter". We discuss efforts to optimize biomolecular motor performance, construct new motors combining artificial and biological components, and contrast biomolecular motors with current artificial molecular motors. A recurrent theme in the work of the past decade was the induction and utilization of collective behavior between motile systems powered by biomolecular motors, and we discuss these advances. The exertion of external control over the motile structures powered by biomolecular motors has remained a topic of many studies describing exciting progress. Finally, we review the current limitations and challenges for the construction of hybrid systems powered by biomolecular motors and try to ascertain if there are theoretical performance limits. Engineering with biomolecular motors has the potential to yield commercially viable devices, but it also sharpens our understanding of the design problems solved by evolution in nature. This increased understanding is valuable for synthetic biology and potentially also for medicine.

Highly efficient decomposition of ammonia using high-entropy alloy catalysts

Ammonia represents a promising liquid fuel for hydrogen storage, but its large-scale application is limited by the need for precious metal ruthenium (Ru) as catalyst. Here we report on highly efficient ammonia decomposition using novel high-entropy alloy (HEA) catalysts made of earth abundant elements. Quinary CoMoFeNiCu nanoparticles are synthesized in a single solid-solution phase with robust control over the Co/Mo atomic ratio, including those ratios considered to be immiscible according to the Co-Mo bimetallic phase diagram. These HEA nanoparticles demonstrate substantially enhanced catalytic activity and stability for ammonia decomposition, with improvement factors achieving >20 versus Ru catalysts. Catalytic activity of HEA nanoparticles is robustly tunable by varying the Co/Mo ratio, allowing for the optimization of surface property to maximize the reactivity under different reaction conditions. Our work highlights the great potential of HEAs for catalyzing chemical transformation and energy conversion reactions.