Energy Conversion Steps Research Articles

Electrocatalytic oxygen reduction at non-metalated and pyrolysis free hypercrosslinked polymers

Oxygen reduction is one of the core steps of non-emissive zero carbon energy conversion. Therefore, enhancement of its sluggish kinetics is extremely important. Very recently researchers focused on oxygen electrocatalysis at porous polymers. Here we applied the non-metalated and pyrolysis free hypercrosslinked polymers with high specific surface area and abundant active sites. Electrode modified with the copolymer prepared from the twisted triphenylbenzene and N containing triphenyl amine exhibits electrocatalytic ORR in alkaline medium. Tafel slope value (0.067 V dec−1) indicates the efficient electrocatalytic activity and fast reaction kinetics. The lack of H2O2 product detected by scanning electrochemical microscopy suggests 4-electron path. The electrocatalytic activity of electrodes modified with hypercrosslinked polymers prepared from single monomers is also seen.

Optical investigation on lubricant combustion characteristics under the ammonia-methane premixed environment

The combustion process is an indispensable energy conversion step in modern industry and energy production. Especially in high-performance engines and energy conversion systems, understanding and controlling the combustion process is critical to improving efficiency and reducing environmental pollution. As a key component of mechanical systems, the combustion characteristics of lubricants at high temperatures and pressures have a direct impact on system performance and emissions. This study investigated the combustion characteristics of lubricant films in an ammonia-methane premixed environment using Planar Laser-Induced Fluorescence (PLIF) and Planar Laser-Induced Incandescence (PLII). It focused on the effects of varying ammonia concentrations on the emission of soot and polycyclic aromatic hydrocarbons (PAHs) in the constant volume combustion vessel. Experiments varied the ammonia-to-methane molar ratios, initial oil film thickness, and base oil type to study their influence on the lubricant combustion characteristics. Results indicated that ammonia significantly reduced soot formation by altering the dynamics of NH* and OH* and impacting PAH distribution. For the lubricating oil soot formation factors, the increase of the initial mean oil film thickness was more obvious for the promotion of soot formation, the increase of the unsaturated hydrocarbon content in the oil film also promoted the generation of carbon soot to a certain extent, and the initial flame energy ratio had the least influence on the promotion of soot formation. Overall, the study contributed to the understanding of the formation mechanism of soot caused by lubricating oil in zero-carbon and low-carbon blended atmospheres and provided a new insight into the interaction between nitrogen-containing zero-carbon fuels and large-carbon-number hydrocarbons, which is of great significance for controlling soot emissions from engines under zero-carbon fuel blending.

Optimizing Energy Consumption: A Case Study of LVDC Nanogrid Implementation in Tertiary Buildings on La Réunion Island

In the context of an insulated area with a subtropical climate, such as La Réunion island, it is crucial to reduce the energy consumption of buildings and develop local renewable energy sources to achieve energy autonomy. Direct current (DC) nanogrids could facilitate this by reducing the energy conversion steps, especially for solar energy. This article presents the deployment and efficiency evaluation of a 48 VDC low-voltage direct current (LVDC) nanogrid, from conception to real-world installation within a company. The nanogrid consists of a photovoltaic power plant, a lithium–iron–phosphate (LFP) battery, and DC end-use equipment, such as LED lighting and DC fans, for two individual offices. For identical test conditions, which are at an equivalent cabling distance and with the same final power demand, the total power consumed by the installation is measured for several stages from 50 to 400 W, according to a 100% DC configuration or a conventional DC/AC/DC PV configuration incorporating an inverter and AC/DC converter. The methodology used enables a critical view to be taken of the installation, assessing both its efficiency and its limitations. Energy savings of between 23% and 40% are measured in DC for a power limit identified at 150 W for a distance of 25 m. These results show that it is possible to supply 48 VDC in an innovative way to terminal equipment consuming no more than 100 W, such as lighting and air fans, using the IEEE 802.3 bt power over ethernet (PoE) protocol, while at the same time saving energy. The nanogrid hardware and software infrastructure, the methodology employed for efficiency quantification, and the measurement results are described in the paper.

Protein assemblies in the Arabidopsis thaliana chloroplast compartment.

Equipped with a photosynthetic apparatus that uses the energy of solar radiation to fuel biosynthesis of organic compounds, chloroplasts are the metabolic factories of mature leaf cells. The first steps of energy conversion are catalyzed by a collection of protein complexes, which can dynamically interact with each other for optimizing metabolic efficiency under changing environmental conditions. For a deeper insight into the organization of protein assemblies and their roles in chloroplast adaption to changing environmental conditions, an improved complexome profiling protocol employing a MS-cleavable cross-linker is used to stabilize labile protein assemblies during the organelle isolation procedure. Changes in protein:protein interaction patterns of chloroplast proteins in response to four different light intensities are reported. High molecular mass assemblies of central chloroplast electron transfer chain components as well as the PSII repair machinery react to different light intensities. In addition, the chloroplast encoded RNA-polymerase complex was found to migrate at a molecular mass of ~8 MDa, well above its previously reported molecular mass. Complexome profiling data produced during the course of this study can be interrogated by interested readers via a web-based online resource (https://complexomemap.de/projectsinteraction-chloroplasts).

Spatially-resolved bioelectrochemistry with scanning electrochemical cell microscopy: A microscale study of coenzyme Q10 modified carbon electrodes

The field of bioelectrochemistry continues to develop due to diverse applications ranging from biosensors to biotechnology and biofuel cells. Accordingly, research understanding the fundamental energy conversion step(s) in these systems (namely electron transfer) will enable the construction of more efficient and better characterised (bio)electrodes. This work investigates surface-confined coenzyme Q10 on glassy carbon (GC-coQ10) and highly ordered pyrolytic graphite (HOPG-coQ10) electrodes using scanning electrochemical cell microscopy (SECCM) in the cyclic voltammetric hopping mode regime. Although frequently studied in bulk at macroscopic electrodes, this is the first report where SECCM has been used to explore how the electrode surfaces employed influences the electrochemical response of immobilised biomolecules in a spatially resolved manner. Full SECCM scans comprised of 1600 cyclic voltammetric measurements on GC-coQ10 and HOPG-coQ10 electrodes demonstrate and quantify the microscopic variability in responses of coQ10 on these surfaces. The HOPG-coQ10 electrode shows a significantly larger distribution of key parameters compared to the GC-coQ10 electrode, such as the voltammetric peak-to-peak separation (∆Ep = 0.87 ± 0.02 V and 0.426 ± 0.008 V on HOPG and GC, respectively) and peak full width at half maximum (e.g., anodic FWHM = 0.25 ± 0.02 V and 0.202 ± 0.003 V on HOPG and GC, respectively). Of note, a unimodal mid-point potential (Emid) distribution is observed for GC-coQ10 (Emid = -0.150 ± 0.002 V vs. Ag|AgCl) whilst a bimodal distribution is seen on HOPG-coQ10 (Emid = -0.11 ± 0.01 and -0.06 ± 0.01 V vs. Ag|AgCl). This study provides a proof of concept that SECCM can be applied to electrode systems commonly used in classical bioelectrochemistry, highlighting the potential of this technique to be used in diverse application areas.

Energy Transition Scenarios in Off-grid Communities using SOFC-CHP/Battery Hybrid Systems

Today, most communities are connected to large energy infrastructures that constitute the electricity and gas grids. But these infrastructures may not be present in extremely low populated regions or regions that are difficult to access, thus considered as off-grid islands or remote regions. Currently, the electricity in these communities is still mostly supplied by centralized or decentralized diesel generators, even though the supplemental use of renewable energy from water, wind and solar is increasingly part of their energy mix. Additionally, centralized or decentralized furnaces, also based on fossil fuels or regenerative fuels (as wood), may be used to supply heat needed for room heating and domestic hot water.The first step for energy transitions towards low emissions in this specific application scenario has the goal to implement prime mover that have higher electrical efficiencies. Consequently, the amount of primary energy (fuel) and the associated CO2 emissions are reduced. Secondly, the efficiency of fuel utilization shall be increased by using the waste heat for room heating, thus representing a typical combined heat and power (CHP) system.While diesel generators are very load flexible, available in different power ranges at reasonable costs their electrical efficiency is limited to 40% or less due to the thermodynamic cycle with several energy conversion steps. Due to the low number of conversions steps in fuel cells, higher electrical efficiencies up to 65% are possible for Solid Oxide Fuel Cell systems specifically. Furthermore, Solid Oxide Fuel Cell systems have a high fuel variety due to operation at high temperatures and enables the CHP operational mode. The overall efficiency of CHP SOFC systems ranges to more than 90%. The main drawback for this technology is the limited flexibility to adapt to load variations, especially regarding start/stop cycles and associated power degradation. To overcome this drawback, batteries in conjunction with SOFC systems may be used for the off-grid scenario.In this regard, SOFC-/Battery Hybrid systems are investigated in an annual simulation analysis for diffent scenarios and 3 different sized example communities. In each scenario waste heat from the SOFC combined with decentralized furnaces is used to fulfill the heat demand.Figure 1 shows the shares of the electrical and the thermal power supplied with a 2.8 MWel SOFC system, the operational states of the system as well as the battery State of Charge (SOC) over one year. It is visible how the battery is charged and discharged and when back-up diesel gensets are necessary to supply sufficient electricity.Based on the annual simulations, the performance and the benefit of using such hybrid systems can be shown in terms of primary energy saving and reduction of CO2 emissions, as well as in terms of system configurations and operation patterns. The analysis also gives information about the necessary sizes of the SOFC systems and the battery capacity to be installed.Figure 1: Exemplary simulation of the SOFC-CHP / Battery Hybrid system with a battery capacity of 2.5 MWh Figure 1

(Nanocarbons Division Robert C. Haddon Research Award) Nano Carbons in Mimicking the Early Events of Photosynthetic Reaction Center: ‘Simple’ and ‘Not-so-Simple’ Donor-Acceptor Conjugates

Light-induced electron transfer is a key step in solar energy conversion, and a process with myriad relevance in the fields of artificial photosynthesis, photocatalysis, photoconductivity, and photovoltaics. In a donor-acceptor, D-A system, light absorption by a chromophore results in the formation of an excited state species, followed by a charge transfer between an electron donor (D) and an electron acceptor (A) leading to a charge-separated D .+ -A .- species.The optimization of these processes and comprehending their mutual interplay to ultimately achieve charge-separated species is of paramount importance for the development of efficient systems in solar light conversion schemes.The present talk summarizes our research over the years focused on utilizing nano carbons, viz., fullerenes, endohedral fullerenes, carbon nanotubes, and graphene in the construction of donor-acceptor systems capable of undergoing photoinduced energy and electron transfer events. Both, covalently linked with rigid, semi-rigid, flexible, or conjugated spacers, and self-assembled via metal-ligand axial coordination, ion-pairing, ion-dipole, or hydrogen bonding strategies were utilized in the construction of donor-acceptor conjugates. Multi-modular donor-acceptor constructs were designed, synthesized, and studied to probe sequential energy and electron transfer events, finally resulting in long-lived charge-separated states. In some instances, these molecular systems were also used as photocatalytic energy conversion schemes. The pros and cons of utilizing nanocarbon materials as photo-active functional materials will be highlighted. D’Souza, F.; Sandanayaka, A. S. D.; Ito, O. ‘SWNT-Based Supramolecular Nanoarchitectures with Photosensitizing Donor and Acceptor Molecules’ Phys. Chem. Letts. 2010, 1. 2586-2593.D’Souza, and O. Ito ‘Photosensitized electron transfer processes of nano carbons applicable to solar cells,’ Chem. Soc. Rev. 2012, 41, 86-96.B. KC, F. D’Souza, ‘Design and photochemical study of supramolecular donor-acceptor systems assembled via metal-ligand axial coordination Coord. Chem. Rev. 2016, 322, 104-141.Bottari, M. A. Herranz, L. Wibmer, M. Vollard, L. Rodriguez-Perez, D. M. Guldi, A. Hirsch, N. Martin, F. D’Souza, T. Torres, Chemical functionalization and characterization of graphene-based materials, Chem. Soc. Rev. 2017, 46, 4464-4500.Barrejon, L. M. Arellano, F. D’Souza, F. Langa, ‘Bidirectional charge transfer in carbon-based hybrid nanomaterials’ Nanoscale, 2019, 11, 14978-14992.Kazemi, Y. Jang, A. Liyanage, P. A. Karr, and F. D’Souza, ‘A Carbon Nanotube Binding Bis(pyrenylstyryl)BODIPY-C60 Nano Tweezer: Charge Stabilization through Sequential Electron Transfer’, Angew. Chem. Int. Ed. 2022, in press

Charge separation in the photosystem II reaction center resolved by multispectral two-dimensional electronic spectroscopy

The photosystem II reaction center (PSII RC) performs the primary energy conversion steps of oxygenic photosynthesis. While the PSII RC has been studied extensively, the similar time scales of energy transfer and charge separation and the severely overlapping pigment transitions in the Qy region have led to multiple models of its charge separation mechanism and excitonic structure. Here, we combine two-dimensional electronic spectroscopy (2DES) with a continuum probe and two-dimensional electronic vibrational spectroscopy (2DEV) to study the cyt b559-D1D2 PSII RC at 77 K.This multispectral combination correlates the overlapping Qy excitons with distinct anion and pigment-specific Qx and mid-infrared transitions to resolve the charge separation mechanism and excitonic structure. Through extensive simultaneous analysis of the multispectral 2D data, we find that charge separation proceeds on multiple time scales from a delocalized excited state via a single pathway in which PheoD1 is the primary electron acceptor, while ChlD1 and PD1 act in concert as the primary electron donor.

An integrated framework for energy performance improvement in manufacturing: From mapping to optimization

Energy performance improvement in manufacturing is hindered by the lack of information on energy use in production and by the predominant economic vision in the assessment of energy interventions. This paper proposes a framework that integrates energy performance mapping with energy systems optimization. The framework introduces a new dimension to energy performance mapping by tracing energy use along processing and energy conversion steps and revisits multi-criteria assessments by assigning penalties to the energy performance gap with best practice. The suitability of food manufacturing for the application of the framework is exemplified from both a top-down and bottom-up perspective. More than 80% reductions in purchased energy carriers and non-renewable energy sources are achieved in a representative process through interventions coupling sector-specific manufacturing knowledge and energy expertise. With regard to one of the interventions, the introduction of the penalty is shown to shift the optimal solution, yielding more than 25% reductions in energy consumption compared to a purely economic assessment. The proposed framework can help industrial stakeholders identify improvement opportunities and develop more sustainable energy systems in manufacturing. Its widespread use can encourage poor performing companies to align with best practice and virtuous companies to continuous innovation to maintain their competitive advantage.

Magnetically Driven Powerless Lighting Device with Kirigami Structured Magneto-Mechanoluminescence Composite.

The energy crisis and global shift toward sustainability drive the need for sustainable technologies that utilize often-wasted forms of energy. A multipurpose lighting device with a simplistic design that does not need electricity sources or conversions can be one such futuristic device. This study investigates the novel concept of a powerless lighting device driven by stray magnetic fields induced by power infrastructure for obstruction warning light systems. The device consists of mechanoluminescence (ML) composites of a Kirigami-shaped polydimethylsiloxane (PDMS) elastomer, ZnS:Cu particles, and a magneto-mechano-vibration (MMV) cantilever beam. Finite element analysis and luminescence characterization of the Kirigami structured ML composites are discussed, including the stress-strain distribution map and comparisons between different Kirigami structures based on stretchability and ML characteristic trade-offs. By coupling a Kirigami-structured ML material and an MMV cantilever structure, a device that can generate visible light as luminescence from a magnetic field can be created. Significant factors that contribute to luminescence generation and intensity are identified and optimized. Furthermore, the feasibility of the device is demonstrated by placing it in a practical environment. This further proves the functionality of the device in harvesting weak magnetic fields into luminescence or light, without complicated electrical energy conversion steps.

Oxygen Evolution/Reduction Reaction Catalysts: From In Situ Monitoring and Reaction Mechanisms to Rational Design

The oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are core steps of various energy conversion and storage systems. However, their sluggish reaction kinetics, i.e., the demanding multielectron transfer processes, still render OER/ORR catalysts less efficient for practical applications. Moreover, the complexity of the catalyst-electrolyte interface makes a comprehensive understanding of the intrinsic OER/ORR mechanisms challenging. Fortunately, recent advances of in situ/operando characterization techniques have facilitated the kinetic monitoring of catalysts under reaction conditions. Here we provide selected highlights of recent in situ/operando mechanistic studies of OER/ORR catalysts with the main emphasis placed on heterogeneous systems (primarily discussing first-row transition metals which operate under basic conditions), followed by a brief outlook on molecular catalysts. Key sections in this review are focused on determination of the true active species, identification of the active sites, and monitoring of the reactive intermediates. For in-depth insights into the above factors, a short overview of the metrics for accurate characterizations of OER/ORR catalysts is provided. A combination of the obtained time-resolved reaction information and reliable activity data will then guide the rational design of new catalysts. Strategies such as optimizing the restructuring process as well as overcoming the adsorption-energy scaling relations will be discussed. Finally, pending current challenges and prospects toward the understanding and development of efficient heterogeneous catalysts and selected homogeneous catalysts are presented.

A comparative study of sensible energy storage and hydrogen energy storage apropos to a concentrated solar thermal power plant

To achieve dispatchable and reliable power generation through renewable sources, energy storage is often indispensable. This paper attempts a quantitative investigation and comparison between two different energy storage technologies, Thermal Energy Storage System (TESS), which is already mature, and Hydrogen Energy Storage System (HESS), applied to a common concentrated solar thermal power (CSP) plant. A solar field (SF) comprising parabolic troughs and molten salt as a heat transfer fluid is conceived with a power block running on the Rankine cycle. An integrated TESS system is first considered, and the SF size is iteratively determined, so that plant with TESS has a capacity factor of 100 % for a typical summer day, thereby standardizing the TESS performance. The TESS is then replaced with the HESS, keeping the same SF capacity. The plant capacity and storage performances are then compared with simplistic assumptions. The results show superior TESS performance, while HESS delivers only 58 % capacity factor. TESS also delivers superior energy and power density (68 kWh/m3 and 4.5 kW/m3 for TESS, as opposed to 26 kWh/m3 and 1.8 kWh/m3 for HESS, respectively). However, the specific energy and power for both are comparable (approx. 93 Wh/kg and 6 W/kg, respectively). Although electrolyzer and fuel cell efficiencies individually outperform Rankine efficiency, HESS lags in performance with CSP configuration due to multiple steps of energy conversion.

Ultrafast Charge-Transfer in Panchromatic, Push-Pull Porphyrin-Tetracyanobuta-1,3-Diene-Donor Conjugates

Light-induced electron transfer is a key step in solar energy conversion, and a process with myriad relevance in the fields of artificial photosynthesis, photocatalysis, photoconductivity, and molecular photovoltaics. In a donor-acceptor, D-A system, light absorption by a chromophore results in the formation of an excited state species, followed by a charge transfer between an electron donor (D) and an electron acceptor (A) leading to a charge-separated D .+ -A .- species.The optimization of these processes and comprehending their mutual interplay to ultimately achieve charge-separated species is of paramount importance for the development of efficient systems in solar light conversion schemes. As part of our continued effort in this field of research,1-3 using a combination of cycloaddition-retroelectrocyclization reaction, free-base and zinc porphyrins (H2P and ZnP) are decorated at their b-pyrrole positions with strong charge-transfer complexes, viz., tetracyanobuta-1,3-diene (TCBD)-DONOR as a novel class of push-pull systems.4 The physicochemical properties of these compounds have been investigated using a range of electrochemical, spectroelectrochemical, DFT as well as steady-state and time-resolved spectroscopic techniques. Charge transfer interactions between the porphyrin and the electron-withdrawing TCBD directly attached to the porphyrin p-system extended the absorption well into the near-infrared region. The occurrence of photoinduced charge transfer and separation has been established by complementary transient absorption spectral studies followed by global and target data analyses. The role of central metal in the porphyrin cavity and the nature of the donor in governing these photo events will be discussed. Khan, Y. Jang, Y. Patil, R. Misra, and F. D’Souza, Photoinduced Charge Separation Prompted Intervalence Charge Transfer in a Bis(thienyl)diketopyrrolopyrrole Bridged Donor-TCBD Push-Pull System (hot article), Angew. Chem. Int. Ed. 2021, 60, 20518–20527.S. Yadav, A. Z. Alsaleh,R. Misra and F. D’Souza, ‘Excited State Charge Transfer Leading to Charge Stabilization via an Electron Exchange Mechanism in Symmetric, Central Triphenylamine Derived, Dimethylaminophenyl-Tetracyanobutadiene Donor-Acceptor Conjugates, Chem. Sci. 2021, 12, 1109-1120.Pinjari, A. Z. Alsaleh,Y. Patil, R. Misra and F. D’Souza, Interfacing High-Energy Charge Transfer States to a Near-IR Sensitizer for Efficient Electron Transfer upon Near-IR Irradiation’ Angew. Chem. Int. Ed. 2020, 59, 23697-23705.Sekaran, A. Dawson, Y. Jang, K. V. MohanSingh, R. Misra and F. D’Souza, Charge-Transfer in Panchromatic Porphyrin-Tetracyanobuta-1,3-diene-Donor Conjugates: Switching the Role of Porphyrin in the Charge Separation Process, Chem. Eur. J. 2021, 27, 14335-14344 Figure 1

Direct observation of ultrafast exciton localization in an organic semiconductor with soft X-ray transient absorption spectroscopy

The localization dynamics of excitons in organic semiconductors influence the efficiency of charge transfer and separation in these materials. Here we apply time-resolved X-ray absorption spectroscopy to track photoinduced dynamics of a paradigmatic crystalline conjugated polymer: poly(3-hexylthiophene) (P3HT) commonly used in solar cell devices. The π→π* transition, the first step of solar energy conversion, is pumped with a 15 fs optical pulse and the dynamics are probed by an attosecond soft X-ray pulse at the carbon K-edge. We observe X-ray spectroscopic signatures of the initially hot excitonic state, indicating that it is delocalized over multiple polymer chains. This undergoes a rapid evolution on a sub 50 fs timescale which can be directly associated with cooling and localization to form either a localized exciton or polaron pair.

Multi-Phase Heterostructure of CoNiP/Cox P for Enhanced Hydrogen Evolution Under Alkaline and Seawater Conditions by Promoting H2 O Dissociation.

Hydrogen evolution reaction (HER) is a key step for electrochemical energy conversion and storage. Developing well defined nanostructures as noble-metal-free electrocatalysts for HER is promising for the application of hydrogen technology. Herein, it is reported that 3D porous hierarchical CoNiP/Cox P multi-phase heterostructure on Ni foam via an electrodeposition method followed by phosphorization exhibits ultra-highly catalytic activity for HER. The optimized CoNiP/Cox P multi-phase heterostructure achieves an excellent HER performance with an ultralow overpotential of 36mV at 10mA cm-2 , superior to commercial Pt/C. Importantly, the multi-phase heterostructure shows exceptional stability as confirmed by the long-term potential cycles (30,000 cycles) and extended electrocatalysis (up to 500 h) in alkaline solution and natural seawater. Experimental characterizations and DFT calculations demonstrate that the strong electronic interaction at the heterointerface of CoNiP/CoP is achieved via the electron transfer from CoNiP to the heterointerface, which directly promotes the dissociation of water at heterointerface and desorption of hydrogen on CoNiP. These findings may provide deep understanding on the HER mechanism of heterostructure electrocatalysts and guidance on the design of earth-abundant, cost-effective electrocatalysts with superior HER activity for practical applications.

Multiscale modeling and cinematic visualization of photosynthetic energy conversion processes from electronic to cell scales

Conversion of sunlight into chemical energy, namely photosynthesis, is the primary energy source of life on Earth. A visualization depicting this process, based on multiscale computational models from electronic to cell scales, is presented in the form of an excerpt from the fulldome show Birth of Planet Earth. This accessible visual narrative shows a lay audience, including children, how the energy of sunlight is captured, converted, and stored through a chain of proteins to power living cells. The visualization is the result of a multi-year collaboration among biophysicists, visualization scientists, and artists, which, in turn, is based on a decade-long experimental-computational collaboration on structural and functional modeling that produced an atomic detail description of a bacterial bioenergetic organelle, the chromatophore. Software advancements necessitated by this project have led to significant performance and feature advances, including hardware-accelerated cinematic ray tracing and instanced visualizations for efficient cell-scale modeling. The energy conversion steps depicted feature an integration of function from electronic to cell levels, spanning nearly 12 orders of magnitude in time scales. This atomic detail description uniquely enables a modern retelling of one of humanity’s earliest stories—the interplay between light and life.

Analysis of Photo-Intercalation Towards Photo-Charging Lithium-Ion Battery

The energy conversion of light energy into electricity is one of the most promising studies to meet the increasing world energy demands. Solar cell is one of the spread energy devices where light energy converts to electrical energy to be used directly or to be stored as chemical energy for later use by using a rechargeable battery. However, the latter case including two steps of energy conversion in the basic solar cell drives to the low efficiency during device-to-device transfer. The efficient establishment of solar cell technology on a global scale requires an efficient improvement concerning materials and devices to increase the power conversion efficiency. The integration of light-harvesting solar energy with the battery system was expected to enhance the performance of the light energy conversion.The photo-electrochemical reaction of lithium-ion insertion and deinsertion has been reported by employing dye-sensitized battery material under light irradiation [1]. The light energy generated electron-hole pairs with the holes aiding the chemical conversion. Nevertheless, energy efficiency and reaction kinetics should be improved by investigating the appropriate anode material for the system. By utilizing the photo-intercalation and photo-deintercalation concept that has been proposed by H. Tributsch in 1983 [2], the light energy can induce the transfer of ions between the electrode and electrolyte when there is a difference of fermi level energy between electrolyte and electrodes in semiconductor materials. Hence, to investigate the basic fundamental studies of the photo-intercalation reaction, active battery materials and semiconductors were utilized in the photochemical cell. A photo-sensitized LiFePO4 has been prepared to be applied as the working electrode, while a silicon p-type semiconductor has a role as the counter electrode in three electrodes battery system. The electrochemical transparent cell was utilized in order to observe the electrical current response from the energy produced by the reaction that takes place under the light irradiation.The experiment was done by observing the current response of the LiFePO4/Si and the potential changes of LiFePO4 vs. Li+/Li full cell system under light irradiation. There was no electrochemical activation involved in the system. When there was no light irradiation, there was no current response observed. Meanwhile, there was a distinct current and voltage changes marked once the light was irradiating the photochemical cell. For further analysis, the chemical state changes of the electrode materials in the photo-electrochemical system were investigated by conducting an experiment using X-ray absorption spectroscopy. The experiment was done after the irradiation of light energy towards the material. It showed that there was peak changes shape of the X-ray absorption spectrum which corresponds to the lithiation of silicon. By this result, we acquired the possibility of advancing the design principles for photo-assisted rechargeable batteries by using prospective materials.Reference:[1] A. Paolella, et al, Nature Communication, 8 , (2017).[2] H. Tributsch, Solid State Ionics, 9-10 , 41-58 (1983).

Role of Explicitly Included Solvents on Ultrafast Electron Injection and Recombination Dynamics at TiO2/Dye Interfaces.

Solvent effects are important for photovoltaic systems like dye-sensitized solar cells (DSCs) but remain largely unexplored, partly due to the complexity of explicitly including solvent molecules in atomistic simulations. To address these issues, we have systematically investigated the solvent effects in practical solar cells using ab initio excited state dynamics simulations. In this computational protocol and the extended model system, we considered giving a novel perspective on the excited state changes in response to solvation and finite temperature at the heterointerface of DSCs. By directly comparing the geometric stability of interface bonding, photoabsorption, interfacial electronic structure, and dynamics of vacuum and solvent systems, we obtain useful insights into how solvents influence the key factors that determine the efficiency of DSCs. Solvents significantly enhance the intensity of visible light absorption of chromophores (∼2 times) through two effects: (a) by inducing changes to the dye molecule structure due to intermolecular dye-solvent interactions, and (b) by the dielectric screening of the solvent. Furthermore, by adsorbing onto the TiO2 surface, solvent molecules adjust the interfacial band alignment to a favorable level and screen out the attraction force between injected electrons in the semiconductor substrate and holes left on the chromophore to a large extent, dramatically slowing down the recombination process (>8 times). Our findings provide a comprehensive picture of the explicit solvent effects on individual energy conversion steps in DSCs at the microscopic scale and lead to more accurate prediction of the performance of nanodevices in practical environments, contributing to the optimization of realistic renewable energy devices.

Chemisorption as the essential step in electrochemical energy conversion - Review

Growing world population and energy demands have placed energy conversion and storage into the very centre of modern research. Electrochemical energy conversion systems including batteries, fuel cells, and supercapacitors, are widely considered as the next generation power sources. Even though they rely on different mechanisms of energy conversion and storage, fundamentally these are all electrochemical cells, operating through processes taking place at the solid/liquid interfaces, i.e. electrodes. Considering the interfacial nature of electrodes, it is clear that adsorption phenomena cannot be neglected when considering electrochemical systems. More than that, they are of crucial importance for electrochemical processes and represent an essential step in electrochemical energy conversion. In this contribution we give an overview of the phenomena underlying the operation of sustainable metal-ion batteries, fuel cells and supercapacitors, ranging from electrocatalytic reactions and pseudo-faradaic processes to purely adsorptive processes, emphasizing the types, roles and significance of chemisorption. We review experimental and theoretical methods which can provide information about chemisorption in the mentioned systems, stressing the importance of combining both approaches.

Atoms to Phenotypes: Molecular Design Principles of Cellular Energy Metabolism

We report a 100-million atom-scale model of an entire cell organelle, a photosynthetic chromatophore vesicle from a purple bacterium, that reveals the cascade of energy conversion steps culminating in the generation of ATP from sunlight. Molecular dynamics simulations of this vesicle elucidate how the integral membrane complexes influence local curvature to tune photoexcitation of pigments. Brownian dynamics of small molecules within the chromatophore probe the mechanisms of directional charge transport under various pH and salinity conditions. Reproducing phenotypic properties from atomistic details, a kinetic model evinces that low-light adaptations of the bacterium emerge as a spontaneous outcome of optimizing the balance between the chromatophore's structural integrity and robust energy conversion. Parallels are drawn with the more universalmitochondrial bioenergetic machinery, from whence molecular-scale insights into the mechanism of cellular aging are inferred. Together, our integrative method and spectroscopic experiments pave the way to first-principles modeling of whole living cells.