Energy Conversion Devices Research Articles

Chiral Au@CeO2 Helical Nanorods with Spatially Separated Structures for Polarization‐dependent N2 Photofixation

Chiral photocatalytic nanomaterials possess numerous unique properties and hold promise for various applications in chemical synthesis, environmental protection, energy conversion, and photoelectric devices. Nevertheless, it is uncommon to develop effective means to enhance the asymmetric catalytic performances of chiral plasmonic nanomaterials. In this study, a type of L/D‐Au@CeO2 helical nanorods (HNRs) was fabricated by selectively growing CeO2 on the surface of Au HNRs via a facile wet‐chemistry construction method. Chiral Au@CeO2 HNRs, featuring Au and CeO2 with spatially separate structures, exhibited the highest photocatalytic performance for N2 fixation, being 50.80 ± 2.64 times greater than Au HNRs. Furthermore, when L‐Au@CeO2 HNRs corresponded left circularly polarized light (CPL) and D‐Au@CeO2 HNRs corresponded right CPL, their photocatalytic efficiency was enhanced by 3.06 ± 0.06 times in contrast with the samples illuminated with the opposite CPL, which can be attributed to the asymmetrical generation of hot carriers upon CPL excitation. This study not only offered a simple approach to enhance the photocatalytic performance of chiral plasmonic nanomaterials but also demonstrated the potential of chiral plasmonic materials for application in specific photocatalytic reactions, such as N2 fixation.

Modeling solvation dynamics of transition metal redox ion through on-the-fly multi-objective Bayesian-optimized force field.

Modeling solvation dynamics and properties is crucial for developing electrolytes for electrochemical energy storage and conversion devices. This work reports an on-the-fly multi-objective Bayesian optimization (OTF-MOBO) method to parameterize force fields for modeling ionic solvation structures, thermodynamics, and transport properties using molecular dynamics simulations. By leveraging solvation-free energy and solvation radii as training data, we employ the data-driven OTF-MOBO algorithm to actively optimize the force field parameters. The modeling accuracy was evaluated in molecular dynamics simulations until the Pareto front in the parameter space was reached through minimized prediction errors in both solvation-free energy and solvation radii. Using transition metal redox ions (Fe3+/Fe2+, Cr3+/Cr2+, and Cu2+/Cu+) in aqueous solution as examples, we demonstrate that simple force fields combining the Lenard-Jones potential and Coulombic potential can achieve relative error below 2% in both solvation free energy and solvation radii. The optimized force fields can be further extrapolated to predict solvation entropy and diffusivities with relative error below 10% compared with experiments.

Bacterial cellulose materials in sustainable energy devices: A review.

This article provides a comprehensive review of the processing and applications of bacterial cellulose (BC) for energy conversion and storage devices. These emerging technologies enable the transformation of sustainable energy sources into electricity. Once converted, energy storage devices are vital for stable energy supply. To promote green manufacturing practices in this field, bio-based materials are explored as alternative materials for energy devices, addressing the growing demand for sustainable solutions. From a research and development perspective, the materials chosen for energy devices must exhibit exceptional mechanical, electrical, and thermal properties, along with the necessary chemical reactivity to unlock new applications. Furthermore, for successful commercialization and industrialization, these materials must be suitable for large-scale production within practical timeframes. BC fulfills all of these requirements. The review begins with an overview of BC growth, detailing the composition and operating parameters of the culture medium and the design of bioreactors for large-scale production. It then defines and summarizes both in-situ and ex-situ modifications and processing strategies, offering a comprehensive perspective on these techniques. Unique and interesting properties linking BC's structure to its properties are reviewed to demonstrate its potential as a substitute for benchmark materials. The exceptional performance and synergistic effects of BC-derived hybrid materials highlight their potential for state-of-the-art applications in energy devices, and are suitable for the next-generation energy devices. The papers reviewed in this work have gained significant attention and been widely cited over the past 10years for their relevance to various practical applications, allowing readers to have a better understanding in development of BC based materials for energy conversion and conversion devices.

Tailoring Oxygen Reduction Reaction on M-N-C Catalysts via Axial Coordination Engineering.

The development of fuel cells and metal-air batteries is an important link in realizing a sustainable energy supply and a green environment for the future. Oxygen reduction reaction (ORR) is the core reaction of such energy conversion devices. M-N-C catalysts exhibit encouraging ORR catalytic activity and are the most promising candidates for replacing Pt/C. The electrocatalytic performance of M-N-C catalysts is intimately related to the specific metal species and the coordination environment of the central metal atom. Axial coordination engineering presents an avenue for the development of highly active ORR catalysts and has seen considerable progress over the past decade. Nevertheless, the accurate control over the coordination environment and electronic structure of M-N-C catalysts at the atomic scale poses a big challenge. Herein, the diverse axial ligands, characterization techniques, and modulation mechanisms for axial coordination engineering are encompassed and discussed. Furthermore, some pressing matters to be solved and challenges that deserve to be explored and investigated in the future for axial coordination engineering are proposed.

Integration and Characterization of Synthetic Biodegradable Polymer (PVA) with Graphite Oxide (GO) for Performance Assessment in Sustainable Electrochemical Devices

AbstractIn recent years, the demand for sustainable materials in electrochemical devices has driven the exploration of innovative composites. This study focuses on the integration and characterization of synthetic biodegradable polymer polyvinyl alcohol (PVA) with graphite oxide (GO) to evaluate their performance in sustainable electrochemical applications. PVA, known for its biodegradability and biocompatibility, was combined with GO to leverage its excellent electrical conductivity and large surface area. Microbial fuel cells (MFCs) represent a promising electrochemical biosynthesis technology that harnesses the enzymatic activities using microbes to produce energy from organic substrates. This renewable energy approach relies on the synergistic interaction between electrochemically active bacteria and electrode materials to facilitate electron transfer and power generation. Applications of MFCs range from wastewater treatment to sustainable power generation in remote or resource-limited settings. This study explores recent advances in MFC technology, challenges in scaling up for practical applications, and prospects for integrating MFCs into renewable energy strategies. The nano composite membrane was evaluated for structural, morphological, crystalline, and thermal properties by using Fourier Transform Infrared Spectroscopic (FTIR), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and UV- visible spectroscopy. Additionally, the biodegradability of the composite was assessed, confirming that it maintains its environmental benefits while offering improved performance for potential applications in sustainable energy storage and conversion devices. This work provides a promising avenue for the development of eco-friendly electrochemical devices with optimized performance characteristics.

Design and performance study of oscillating hydrofoil-wave energy conversion device

Design and performance study of oscillating hydrofoil-wave energy conversion device

Smart feasibility optimization of hybrid renewable water supply systems by digital twin technologies: A multicriteria approach applied to isolated cities

This research presents a multicriteria approach for the best hybrid water supply solution of a multipurpose Pumped-Storage Hydropower (PSH) system, using the Generalized Reduced Gradient (GRG) method in Solver, with the optimization process considering key factors, such as Net Present Value (NPV), the number of energy conversion devices, renewable energy production, source availability, reservoir capacities, topographic constraints, and energy tariffs. The methodology combines a literature review, methodological development, and machine learning applications for hybrid water-energy systems. Results indicate that solar-only solutions are insufficient in high hydropower potential scenarios while integrating wind turbines significantly enhances energy production and profitability by generating surplus energy for grid sales. The timing of energy sales and the incorporation of battery storage also impact NPV, which can exceed 180 million euros. Wind energy contributes to continuous profitability and optimized system performance, particularly in isolated regions. The PSH system can manage 130,000 cubic meters of water daily, storing 25 MWh of energy, and reducing CO2 emissions by over 18,000 tonnes per year. These findings highlight the importance of renewables, such as wind energy, and effective operational management. It enhances the economic viability and environmental sustainability of hybrid water-energy systems.

Stainless Steel Mesh in Electrochemistry: Comprehensive Applications and Future Prospects.

Stainless steel mesh (SSM) has emerged as a cornerstone in electrochemical applications owing to its exemplary versatility, electrical conductivity, mechanical robustness, and corrosion resistance. This state-of-the-art review delves into the diverse roles of SSM across a spectrum of electrochemical domains, including energy conversion and storage devices, water treatment technologies, electrochemical sensors, and catalysis. We meticulously explore its deployment in supercapacitors, batteries, and fuel cells, highlighting its utility as a current collector, electrode, and separator. The review further discusses the critical significance of SSM in water treatment processes, emphasizing its efficacy in supporting membranes and facilitating electrocoagulation, as well as its novel uses in electrochemical sensing and catalysis, which include electrosynthesis and bioelectrochemistry. Each section delineates the recent advancements, identifies the inherent challenges, and suggests future directions for leveraging SSM in electrochemical technologies. This comprehensive review showcases the current state of knowledge and articulates the novel integration of SSM with emerging materials and technologies, thereby establishing a new paradigm for sustainable and efficient electrochemical applications. Through critical analysis and insightful recommendations, this review positions itself as a seminal contribution, paving the way for researchers and practitioners to harness the full potential of SSM in advancing the electrochemistry frontiers.

Recommended practice for measurement and evaluation of oxygen evolution reaction electrocatalysis

AbstractThe Oxygen evolution reaction (OER) is a pivotal technology driving next‐generation sustainable energy conversion and storage devices. Establishing a robust analytical methodology is paramount to fostering innovation in this field. This review offers a comprehensive discussion on measurement and interpretation, advocating for standardized protocols and best practices to mitigate the myriad factors that complicate analysis. The initial focus is directed toward substrate electrodes and gas bubbles, both significant contributors to reduced reliability and reproducibility. Subsequently, the review focuses on intrinsic activity assessment, identification of electrochemical active sites, and the disentanglement of competing process contributions. These careful methodologies ensure the systematic delivery of insights crucial for assessing OER performance. In conclusion, the review highlights the critical role played by precise measurement techniques and unbiased activity comparison methodologies in propelling advancements in OER catalyst development.image

High-performance porous activated carbon derived from Acacia catechu bark as nanoarchitectonics material for supercapacitor applications

BackgroundThe increasing energy demands stemming from the extensive utilization of portable electronic devices are creating a huge energy deficit between demand and supply. In this scenario, it is not only sufficient to pursue and innovate the new renewable energy sources but also requires an ideal device for energy storage and conversion. MethodsIn this work, activated carbon (AC) was prepared from matured bark of Acacia catechu through a series of steps; pre-carbonization, carbonization, and activation. The AC was synthesized at different temperatures (400–800 °C) under inert atmosphere, using orthophosphoric acid as an activator. As-prepared sample (ACBH) was characterized by well-known characterization techniques. Energy storage capability was assessed in terms of Cyclic voltammetry, Galvanostatic charge-discharge, Electrochemical impedance, and Cyclic stability by three-electrode setup. Significant findingsThe ACBH-8 sample demonstrated superior electrochemical performance compared to other samples. The sample ACBH-8, as Negatrode, exhibited a specific capacitance of 282.4 F g−1 at 0.5 A g−1 and retained 95.4 % cyclic stability under 10,000 cycles. The excellent energy storage performance by green-class negatrode materials from the bio-waste substance empowers commercial applications.

Probing the structural evolution of cobalt hydroxide in electrochemical water splitting.

Transition-metal hydroxides are a category of earth-abundant and stable electrocatalysts for energy storage and conversion devices involving sluggish oxygen evolution reaction (OER). Understanding dynamic evolution at the solid/liquid interface of transition-metal hydroxides is crucial for the rational design of high-performance OER electrocatalysts. This study implemented in situ electrochemical atomic force microscopy (EC-AFM) to directly image the dynamic structural evolution of α-Co(OH)2 platelets during the electrochemical OER. Reconstruction of α-Co(OH)2, accompanied by ion insertion from the electrolyte, results in a volume expansion, which can be well confirmed from the X-ray diffraction patterns. Our findings are important for the fundamental understanding of transition-metal hydroxide oxygen-evolution catalysts, illustrating the dynamic nature of Co-based nanostructures under electrochemical conditions.

Design and regulation of defective electrocatalysts.

Electrocatalysts are the key components of electrochemical energy storage and conversion devices. High performance electrocatalysts can effectively reduce the energy barrier of the chemical reactions, thereby improving the conversion efficiency of energy devices. The electrocatalytic reaction mainly experiences adsorption and desorption of molecules (reactants, intermediates and products) on a catalyst surface, accompanied by charge transfer processes. Therefore, surface control of electrocatalysts plays a pivotal role in catalyst design and optimization. In recent years, many studies have revealed that the rational design and regulation of a defect structure can result in rearrangement of the atomic structure on the catalyst surface, thereby efficaciously promoting the electrocatalytic performance. However, the relationship between defects and catalytic properties still remains to be understood. In this review, the types of defects, synthesis methods and characterization techniques are comprehensively summarized, and then the intrinsic relationship between defects and electrocatalytic performance is discussed. Moreover, the application and development of defects are reviewed in detail. Finally, the challenges existing in defective electrocatalysts are summarized and prospected, and the future research direction is also suggested. We hope that this review will provide some principal guidance and reference for researchers engaged in defect and catalysis research, better help researchers understand the research status and development trends in the field of defects and catalysis, and expand the application of high-performance defective electrocatalysts to the field of electrocatalytic engineering.

Analysis of the electromechanical responses of sandwich circular nano-plate based on flexoelectric nano-ultrasonic transducer

Flexoelectric nano-ultrasonic transducer is an important development direction of ultra-high frequency ultrasonic transducers. The key to its development lies in addressing the electromechanical coupling dynamics of a flexoelectric nano-element, that is, sandwich circular nano-plate. In this paper, a novel dynamic theoretical model of sandwich circular nano-plate is developed based on the transversely isotropic flexoelectricity couple stress and Kirchhoff plate theories. Based on the novel model, this study demonstrates the influence of flexoelectricity effect and size effect on its electromechanical responses of the core component in the nano-ultrasonic transducer. Simultaneously, using finite element software, the paper presents the first six mode shapes of the structure and reveals the mode shape most conducive to the energy conversion of the transducer. The main objective of this study is to provide a theoretical foundation for the development of nano-ultrasonic transducers based on flexoelectric materials. The novel model can also be applied in various energy conversion devices, including flexoelectric actuator and flexoelectric energy harvesters.

Covalent Immobilization of Mediators on Photoelectrodes for NADH Regeneration.

The reduced nicotinamide adenine dinucleotide (NADH) is a vital biomolecule involved in many biocatalytic processes, and the high cost makes it significant to regenerate NADH in vitro. The photoelectrochemical approach is a promising and environmentally friendly method for sustainable NADH regeneration. However, the free Rh-based mediator ([Cp*Rh (bpy)H2O]2+) in the electrolyte suffers from low efficiency due to the sluggish charge transfer controlled by the diffusion process. Herein, we report an efficient and facile covalent bonding of the Rh-based mediator with the Si-based photocathode for NADH regeneration. The bipyridine-containing covalent organic framework (BpyCOF) layer ensures the even distribution of mediators throughout the surface of the photoelectrode. The graphene interlayer provides a pathway for charge transport and prevents silicon from corrosion. Furthermore, during the synthesis of BpyCOF, it functions as a substrate to promote the growth of the oriented BpyCOF film. The imitated contact between the components of the photocathode favors the charge transfer to the surface to participate in a chemical reaction, thus improving the catalytic performance and the NADH regeneration efficiency, which is four times higher than the reported photocathode modified by the Rh-based mediator. This study offers a new strategy for the construction of photoelectrochemical solar energy conversion devices.

Recent advantages on mass transfer structure construction in transition metal‐based cost‐effective catalyst toward alkaline oxygen evolution

The electrochemical oxygen evolution reaction (OER) can be combined with various reactions to fabricate electrochemical energy conversion and storage devices while the slow kinetics and poor mass transfer capability at high current densities were the key constraints to its large‐scale application. Therefore, this review primarily focuses on design and optimization of mass transfer structures of TM‐metal‐based OER catalysts. Nanostructuring, porous design, and the creation of hierarchical architectures have been applied during catalyst synthesis to enhance the surface area and accessibility, thereby improving mass transfer and catalytic OER efficiency. Strategies including doping, substrate invitation, soft/hard templating has been utilized to accelerate mass transfer as well as the ion/electron conduction efficiency for the overall improvement of OER performance of the catalysts. These developments underline the critical role of advanced material design in achieving high‐performance OER catalysts and highlight the potential of TM‐based materials in cost‐effective and scalable applications.

Low temperature rotary Stirling engine: Conceptual design and theoretical analysis

The use of low-temperature energy sources for electricity generation demands a dual focus: a substantial enhancement in the efficiency of energy conversion devices and a reduction in system production costs. Particularly in scenarios where low-temperature energy sources are scarce, this factor can be pivotal in facilitating widespread adoption of such technologies. The Stirling engine emerges as a promising solution capable of meeting these articulated expectations, owing to its straightforward design and utilization of non-toxic, non-flammable, and cost-effective working mediums. This paper introduces a novel concept of a rotary Stirling engine, exhibiting significant potential for operation with low-temperature energy sources. Additionally, an analytical model of the engine is presented, enabling simulations of its operation under varying supply temperatures and geometric configurations. To analyse the impact of internal leaks on the net efficiency and net power of the engine, a modified adiabatic model was introduced. It was observed that utilizing identical heat exchangers for heat supply at 250 °C and 100 °C could lead to a decline in net efficiency from 8 % to 3 % for the worst case. Furthermore, an analysis was performed to assess the impact of the heater’s overall heat transfer coefficient and engine rotational speed on both net efficiency and net mechanical power for a heat supply temperature of 200 °C.

Enhanced Electron Emission Performance and Air-Surface Stability in ScO-Terminated Diamond for Thermionic Energy Converters.

Diamond with negative electron affinity (NEA) and low work function surfaces are suggested as a suitable material for electron-generation applications in vacuum, in particular, as the emitter electrode in thermionic energy converters. Such NEA surfaces can be fabricated by evaporating and then annealing submonolayers of a suitable metal in vacuo onto bare or oxidized diamond. Among the metals studied, scandium termination of bare diamond (100) and (111) surfaces is recently reported to give the largest NEA values reported to date for a metal-diamond system, as well as being thermally stable to 900°C. It is now shown that preoxidized (100) diamond functionalized with 0.25monolayers of Sc also produces a large NEA value of -1.02eV with low work functions (<3.63eV). Moreover, this surface is thermally stable to 700°C and can withstand exposure to air for extended periods. Here, the structural and electronic properties of this Sc─O-functionalized diamond surface are characterized in detail using a variety of surface-science techniques. The results suggest that this material may be the ideal candidate for the fabrication of commercial thermionic energy conversion devices, e.g., for solar-power generation, as well as for various other electronic devices that rely upon electron emission.

Fabrication of bio-abiotic hybrid living hydrogel for bifunctional electrochemical conversion

Design and intelligent use renewable natural bioenergy is an important challenge. Electric microorganism-based materials are being serve as an important part of bioenergy devices for energy release and collection, calling for suitable skeleton materials to anchor live microbes. Herein we verified the feasibility of constructing bio-abiotic hybrid living materials based on the combination of gelatin, Li-ions and exoelectrogenic bacteria Shewanella oneidensis manganese-reducing-1 (MR-1). The gelatin-based mesh contains abundant pores, allowing microbes to dock and small molecules to diffuse. The hybrid materials hold plentiful electronegative groups, which effectively anchor Li-ions and facilitate their transition. Moreover, the electrochemical characteristics of the materials can be modulated through changing the ratios of gelatin, bacteria and Li-ions. Based on the gelatin-Li-ion-microorganism hybrid materials, a bifunctional device was fabricated, which could play dual roles alternatively, generation of electricity as a microbial fuel cell and energy storage as a pseudocapacitor. The capacitance and the maximum voltage output of the device reaches 68 F·g-1 and 0.67 V, respectively. This system is a new platform and fresh start to fabricate bio-abiotic living materials for microbial electron storage and transfer. We expect the setup will extend to other living systems and devices for synthetic biological energy conversion.

Boosting hydrogen production via alkaline water splitting: Impact of Ag doping in Gd2O3 nanosheet arrays

Hydrogen is a preferable renewable energy carrier in decarbonization efforts to develop sustainable and carbon-free economies due to its high energy density and absence of pollutant emissions during combustion. Among others, electrochemical water splitting (EWS) is a sustainable and eco-friendly technology for producing green hydrogen, representing an essential initial step towards achieving carbon neutrality. In this study, we synthesized a bifunctional electrocatalyst by vertically anchoring Ag-doped Gd2O3 nanosheet arrays onto a three-dimensional nickel foam (NF) substrate. The developed materials were thoroughly investigated using various analytical techniques. Furthermore, the electrocatalyst effectively performed oxygen evolution reactions (OER) and hydrogen evolution reactions (HER). The Ag4%-Gd2O3/NF exhibited boosted HER activity, achieving higher current densities ranging from 10 to 400 mA cm−2 at an overpotential between 14 and 122 mV. This study also highlights the considerable impact of metal sites in both Ag4%-Gd2O3/NF and Gd2O3/NF on the HER catalytic process. Similarly, the Ag4%-Gd2O3 electrocatalyst exhibited superior OER activity, with an overpotential of 209 mV at 10 mA cm−2. The optimized composition also shows Tafel slope of 25 and 20 mVdec−1. Furthermore, Ag4%-Gd2O3 demonstrated the ability to generate oxygen gas bubbles in approximately 20 h for OER, making it an attractive material for energy conversion and storage devices.

Deep learning performance prediction for solar-thermal-driven hydrogen production membrane reactor via bayesian optimized LSTM

The random fluctuation of solar energy poses significant challenges for direct solar utilization systems. Solar-driven membrane reactors (SMMR) are efficient devices for energy conversion and pure hydrogen production, featuring thermal inertia and complex physicochemical processes. To realize advance control of SMMR under solar variations to promote their practical application, accurate performance prediction is essential. This study develops a deep learning-assisted performance prediction model for SMMR using Bayesian optimized long short-term memory (BO-LSTM) network and weather classification. Time-series datasets with similar environmental features are generated through SMMR multi-physics modeling and trained by BO-LSTM. The BO-LSTM demonstrates high accuracy in both short-time (1-day) and long-time (40-day) predictions, with a correlation coefficient exceeding 0.997 and a deviation of ±0.0016 in long-term predictions. Weather classification ensures consistent prediction accuracy across different weather. Compared to RF, SVM, BPNN, and CNN models, BO-LSTM provides smoother prediction curves and significantly improves accuracy and stability, reducing RMSE by 44.6% on sunny days and 53.3% on cloudy days in short-time predictions, and by 56.7% and 68.0% in long-time predictions, respectively. The BO-LSTM proposed in this study accurately predicts SMMR performance under various weather, guiding practical applications and offering a reference for prediction and control in solar thermal utilization systems.