Advance in Energy Conversion and Storage: Material, Design and Application

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "E:Engineering and Technology".

Deadline for manuscript submissions: closed (31 May 2023) | Viewed by 11159

Special Issue Editors

Department of Mechanical Engineering, The University of Hong Kong, Pokfulam 999077, Hong Kong
Interests: metal-ion/air batteries; advanced electrolytes; ion intercalation chemistry
Special Issues, Collections and Topics in MDPI journals
Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213, USA
Interests: metal air batteries; thermal electrochemical cells; photovoltaic electrochemical cells
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Energy issue has long been a concern for the modern society. For energy storage market, Li-ion batteries has achieved significant success and thus dominate the market, however, a series of issues like limited lithium resources restricted its further development. Thus, several emerging battery technics are attracting more and more research and industrial interests, some of which are expected to become the next generation energy storage devices, including other metal-based ion batteries (such as non-aqueous Na/K-ion batteries and aqueous Zn/Al ion batteries), metal-sulfur batteries and redox flow batteries. They have achieved tremendous success in laboratory scale and some prototypes has even been commercialized over the past 5 years. Moreover, surprising development has been achieved in the energy conversion aspect by great efforts. Various kinds of fuel cells achieved powerful energy output with higher and higher energy efficiencies; thermoelectric generator systems show a blueprint of waste heat utilization; CO2 reduction cells are promising to curb the carbon emissions and give value-added products back. Although these technologies are under rapid development, there still exists big challenges to make these efforts into practical applications. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on (1) energy conversion discipline, including fuel cells, CO2 reduction cells and other energy generators; and (2) energy storage aspect, including ion batteries, supercapacitors and redox flow batteries.

We look forward to receiving your submissions! 

Dr. WenDing Pan
Dr. Rui Cheng
Guest Editors

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Keywords

  • ion batteries
  • flow batteries
  • fuel cells
  • CO2 reduction and utilization
  • other energy conversion and storage devices

Published Papers (9 papers)

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Research

18 pages, 6088 KiB  
Article
Improvement of Hybrid Electrode Material Synthesis for Energy Accumulators Based on Carbon Nanotubes and Porous Structures
by Boris V. Malozyomov, Vladislav V. Kukartsev, Nikita V. Martyushev, Viktor V. Kondratiev, Roman V. Klyuev and Antonina I. Karlina
Micromachines 2023, 14(7), 1288; https://doi.org/10.3390/mi14071288 - 23 Jun 2023
Cited by 30 | Viewed by 984
Abstract
Carbon materials are promising for use as electrodes for supercapacitors and lithium–ion batteries due to a number of properties, such as non-toxicity, high specific surface area, good electronic conductivity, chemical inertness, and a wide operating temperature range. Carbon-based electrodes, with their characteristic high [...] Read more.
Carbon materials are promising for use as electrodes for supercapacitors and lithium–ion batteries due to a number of properties, such as non-toxicity, high specific surface area, good electronic conductivity, chemical inertness, and a wide operating temperature range. Carbon-based electrodes, with their characteristic high specific power and good cyclic stability, can be used for a new generation of consumer electronics, biomedical devices and hybrid electric vehicles. However, most carbon materials, due to their low electrical conductivity and insufficient diffusion of electrolyte ions in complex micropores, have energy density limitations in these devices due to insufficient number of pores for electrolyte diffusion. This work focuses on the optimization of a hybrid material based on porous carbon and carbon nanotubes by mechanical mixing. The purpose of this work is to gain new knowledge about the effect of hybrid material composition on its specific capacitance. The material for the study is taken on the basis of porous carbon and carbon nanotubes. Electrodes made of this hybrid material were taken as an object of research. Porous carbon or nitrogen-containing porous carbon (combined with single-, double-, or multi-layer carbon nanotubes (single-layer carbon nanotubes, bilayer carbon nanotubes or multilayer carbon nanotubes) were used to create the hybrid material. The effect of catalytic chemical vapor deposition synthesis parameters, such as flow rate and methane-to-hydrogen ratio, as well as the type of catalytic system on the multilayer carbon nanotubes structure was investigated. Two types of catalysts based on Mo12O282-OH)12{Co(H2O)3}4 were prepared for the synthesis of multilayer carbon nanotubes by precipitation and combustion. The resulting carbon materials were tested as electrodes for supercapacitors and lithium ion intercalation. Electrodes based on nitrogen-containing porous carbon/carbon nanotubes 95:5% were found to be the most efficient compared to nitrogen-doped porous carbon by 10%. Carbon nanotubes, bilayer carbon nanotubes and multilayer carbon nanotubes synthesized using the catalyst obtained by deposition were selected as additives for the hybrid material. The hybrid materials were obtained by mechanical mixing and dispersion in an aqueous solution followed by lyophilization to remove water. When optimizing the ratio of the hybrid material components, the most effective porous carbon:carbon nanotubes component ratio was determined. Full article
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12 pages, 6706 KiB  
Article
Development of a Novel Piezoelectric Actuator Based on Stick–Slip Principle by Using Asymmetric Constraint
by Liang Wang, Heran Wang, Junxiang Jiang and Tianwen Luo
Micromachines 2023, 14(6), 1140; https://doi.org/10.3390/mi14061140 - 28 May 2023
Cited by 2 | Viewed by 1395
Abstract
In this work, a novel piezoelectric actuator based on the stick–slip principle is proposed. The actuator is constrained by an asymmetric constraint approach; the driving foot produces lateral and longitudinal coupling displacements when the piezo stack is extended. The lateral displacement is used [...] Read more.
In this work, a novel piezoelectric actuator based on the stick–slip principle is proposed. The actuator is constrained by an asymmetric constraint approach; the driving foot produces lateral and longitudinal coupling displacements when the piezo stack is extended. The lateral displacement is used to drive the slider and the longitudinal displacement is used to compress the slider. The stator part of the proposed actuator is illustrated and designed by simulation. The operating principle of the proposed actuator is described in detail. The feasibility of the proposed actuator is verified by theoretical analysis and finite element simulation. A prototype is fabricated and some experiments are carried out to study the proposed actuator’s performance. The experimental results show that the maximum output speed of the actuator is 3680 μm/s when the locking force is 1 N under the voltage of 100 V and frequency of 780 Hz. The maximum output force is 3.1 N when the locking force is 3 N. The displacement resolution of the prototype is measured as 60 nm under the voltage of 15.8 V, frequency of 780 Hz and locking force of 1 N. Full article
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16 pages, 6485 KiB  
Article
The Design and Experiment of a Spring-Coupling Electromagnetic Galloping Energy Harvester
by Lei Xiong, Shiqiao Gao, Lei Jin, Shengkai Guo, Yaoqiang Sun and Feng Liu
Micromachines 2023, 14(5), 968; https://doi.org/10.3390/mi14050968 - 28 Apr 2023
Cited by 3 | Viewed by 838
Abstract
In order to improve the output characteristics of the electromagnetic energy harvester in a high-speed flow field, a spring-coupling electromagnetic energy harvester (SEGEH) is proposed, based on the galloping characteristics of a large amplitude. The electromechanical model of the SEGEH was established, the [...] Read more.
In order to improve the output characteristics of the electromagnetic energy harvester in a high-speed flow field, a spring-coupling electromagnetic energy harvester (SEGEH) is proposed, based on the galloping characteristics of a large amplitude. The electromechanical model of the SEGEH was established, the test prototype was made, and the experiments were conducted using a wind tunnel platform. The coupling spring can convert the vibration energy consumed by the vibration stroke of the bluff body without inducing an electromotive force into the elastic energy of the spring. This not only reduces the galloping amplitude, but it also provides elastic force for the return of the bluff body, and it improves the duty cycle of the induced electromotive force and the output power of the energy harvester. The stiffness of the coupling spring and the initial distance between the coupling spring and the bluff body will affect the output characteristics of the SEGEH. At a wind speed of 14 m/s, the output voltage was 103.2 mV and the output power was 0.79 mW. Compared with the energy harvester without a coupling spring (EGEH), the output voltage increases by 29.4 mV, with an increase of 39.8%. The output power was increased by 0.38 mW, with an increase of 92.7%. Full article
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11 pages, 2522 KiB  
Article
Unexpected Negative Performance of PdRhNi Electrocatalysts toward Ethanol Oxidation Reaction
by Ahmed ElSheikh and James McGregor
Micromachines 2023, 14(5), 957; https://doi.org/10.3390/mi14050957 - 27 Apr 2023
Viewed by 1022
Abstract
Direct ethanol fuel cells (DEFCs) need newly designed novel affordable catalysts for commercialization. Additionally, unlike bimetallic systems, trimetallic catalytic systems are not extensively investigated in terms of their catalytic potential toward redox reactions in fuel cells. Furthermore, the Rh potential to break the [...] Read more.
Direct ethanol fuel cells (DEFCs) need newly designed novel affordable catalysts for commercialization. Additionally, unlike bimetallic systems, trimetallic catalytic systems are not extensively investigated in terms of their catalytic potential toward redox reactions in fuel cells. Furthermore, the Rh potential to break the ethanol rigid C-C bond at low applied potentials, and therefore enhance the DEFC efficiency and CO2 yield, is controversial amongst researchers. In this work, two PdRhNi/C, Pd/C, Rh/C and Ni/C electrocatalysts are synthesized via a one-step impregnation process at ambient pressure and temperature. The catalysts are then applied for ethanol electrooxidation reaction (EOR). Electrochemical evaluation is performed using cyclic voltammetry (CV) and chronoamperometry (CA). Physiochemical characterization is pursued using X-ray diffraction (XRD), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Unlike Pd/C, the prepared Rh/C and Ni/C do not show any activity for (EOR). The followed protocol produces alloyed dispersed PdRhNi nanoparticles of 3 nm in size. However, the PdRhNi/C samples underperform the monometallic Pd/C, even though the Ni or Rh individual addition to it enhances its activity, as reported in the literature herein. The exact reasons for the low PdRhNi performance are not fully understood. However, a reasonable reference can be given about the lower Pd surface coverage on both PdRhNi samples according to the XPS and EDX results. Furthermore, adding both Rh and Ni to Pd exercises compressive strain on the Pd lattice, noted by the PdRhNi XRD peak shift to higher angles. Full article
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18 pages, 6476 KiB  
Article
Electrode Based on the MWCNTs and Electropolymerized Thymolphthalein for the Voltammetric Determination of Total Isopropylmethylphenols in Spices
by Natalia Chernousova and Guzel Ziyatdinova
Micromachines 2023, 14(3), 636; https://doi.org/10.3390/mi14030636 - 11 Mar 2023
Cited by 1 | Viewed by 1114
Abstract
Isopropylmethylphenols, namely thymol and carvacrol, are natural phenolic monoterpenoids with a wide spectrum of bioactivity making them applicable in the cosmetic, pharmaceutical, and food industry. The dose-dependent antioxidant properties of isopropylmethylphenols require their quantification in real samples. Glassy carbon electrode (GCE) modified with [...] Read more.
Isopropylmethylphenols, namely thymol and carvacrol, are natural phenolic monoterpenoids with a wide spectrum of bioactivity making them applicable in the cosmetic, pharmaceutical, and food industry. The dose-dependent antioxidant properties of isopropylmethylphenols require their quantification in real samples. Glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNTs) and electropolymerized thymolphthalein has been developed for the sensitive quantification of isopropylmethylphenols. Conditions of thymolphthalein electropolymerization (monomer concentration, number of cycles, and electrolysis parameters) providing the best response to thymol have been found. Scanning electron microscopy and electrochemical methods confirm the effectivity of the electrode developed. The linear dynamic ranges of 0.050–25 and 25–100 µM for thymol and 0.10–10 and 10–100 µM for carvacrol with detection limits of 0.037 and 0.063 µM, respectively, have been achieved in differential pulse mode in Britton–Robinson buffer pH 2.0. The selectivity of the isopropylmethylphenols response in the presence of typical interferences (inorganic ions, saccharides, ascorbic acid) and other phenolics (caffeic, chlorogenic, gallic and rosmarinic acids, and quercetin) is a significant advantage over other electrochemical methods. The electrode has been used in the analysis of oregano and thyme spices. Total isopropylmethylphenols contents have been evaluated after a single sonication-assisted extraction with methanol. Full article
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13 pages, 4512 KiB  
Article
Iron-Vanadium Incorporated Ferrocyanides as Potential Cathode Materials for Application in Sodium-Ion Batteries
by Thang Phan Nguyen and Il Tae Kim
Micromachines 2023, 14(3), 521; https://doi.org/10.3390/mi14030521 - 23 Feb 2023
Cited by 1 | Viewed by 1506
Abstract
Sodium-ion batteries (SIBs) are potential replacements for lithium-ion batteries owing to their comparable energy density and the abundance of sodium. However, the low potential and low stability of their cathode materials have prevented their commercialization. Prussian blue analogs are ideal cathode materials for [...] Read more.
Sodium-ion batteries (SIBs) are potential replacements for lithium-ion batteries owing to their comparable energy density and the abundance of sodium. However, the low potential and low stability of their cathode materials have prevented their commercialization. Prussian blue analogs are ideal cathode materials for SIBs owing to the numerous diffusion channels in their 3D structure and their high potential vs. Na/Na+. In this study, we fabricated various Fe-V-incorporated hexacyanoferrates, which are Prussian blue analogs, via a one-step synthesis. These compounds changed their colors from blue to green to yellow with increasing amounts of incorporated V ions. The X-ray photoelectron spectroscopy spectrum revealed that V3+ was oxidized to V4+ in the cubic Prussian blue structure, which enhanced the electrochemical stability and increased the voltage platform. The vanadium ferrocyanide Prussian blue (VFPB1) electrode, which contains V4+ and Fe2+ in the Prussian blue structure, showed Na insertion/extraction potential of 3.26/3.65 V vs. Na/Na+. The cycling test revealed a stable capacity of ~70 mAh g−1 at a rate of 50 mA g−1 and a capacity retention of 82.5% after 100 cycles. We believe that this Fe-V-incorporated Prussian green cathode material is a promising candidate for stable and high-voltage cathodes for SIBs. Full article
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11 pages, 3130 KiB  
Article
Studies of Performance of Cs2TiI6−XBrX (Where x = 0 to 6)-Based Mixed Halide Perovskite Solar Cell with CdS Electron Transport Layer
by Kunal Chakraborty, Nageswara Rao Medikondu, Kumutha Duraisamy, Naglaa F. Soliman, Walid El-Shafai, Sunil Lavadiya, Samrat Paul and Sudipta Das
Micromachines 2023, 14(2), 447; https://doi.org/10.3390/mi14020447 - 14 Feb 2023
Cited by 1 | Viewed by 1316
Abstract
The present research work represents the numerical study of the device performance of a lead-free Cs2TiI6−XBrX-based mixed halide perovskite solar cell (PSC), where x = 1 to 5. The open circuit voltage (VOC) and short [...] Read more.
The present research work represents the numerical study of the device performance of a lead-free Cs2TiI6−XBrX-based mixed halide perovskite solar cell (PSC), where x = 1 to 5. The open circuit voltage (VOC) and short circuit current (JSC) in a generic TCO/electron transport layer (ETL)/absorbing layer/hole transfer layer (HTL) structure are the key parameters for analyzing the device performance. The entire simulation was conducted by a SCAPS-1D (solar cell capacitance simulator- one dimensional) simulator. An alternative FTO/CdS/Cs2TiI6−XBrX/CuSCN/Ag solar cell architecture has been used and resulted in an optimized absorbing layer thickness at 0.5 µm thickness for the Cs2TiBr6, Cs2TiI1Br5, Cs2TiI2Br4, Cs2TiI3Br3 and Cs2TiI4Br2 absorbing materials and at 1.0 µm and 0.4 µm thickness for the Cs2TiI5Br1 and Cs2TiI6 absorbing materials. The device temperature was optimized at 40 °C for the Cs2TiBr6, Cs2TiI1Br5 and Cs2TiI2Br4 absorbing layers and at 20 °C for the Cs2TiI3Br3, Cs2TiI4Br2, Cs2TiI5Br1 and Cs2TiI6 absorbing layers. The defect density was optimized at 1010 (cm−3) for all the active layers. Full article
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13 pages, 2497 KiB  
Article
Vibration-Assisted Synthesis of Nanoporous Anodic Aluminum Oxide (AAO) Membranes
by Urte Cigane, Arvydas Palevicius and Giedrius Janusas
Micromachines 2022, 13(12), 2236; https://doi.org/10.3390/mi13122236 - 16 Dec 2022
Cited by 2 | Viewed by 1112
Abstract
In recent years, many research achievements in the field of anodic aluminum oxide (AAO) membranes can be observed. Nevertheless, it is still an interesting research topic due to its high versatility and applications in various fields, such as template-assisted methods, filtration, sensors, etc. [...] Read more.
In recent years, many research achievements in the field of anodic aluminum oxide (AAO) membranes can be observed. Nevertheless, it is still an interesting research topic due to its high versatility and applications in various fields, such as template-assisted methods, filtration, sensors, etc. Nowadays, miniaturization is an integral part of different technologies; therefore, research on micro- and nanosized elements is relevant in areas such as LEDs and OLEDs, solar cells, etc. To achieve an efficient mixing process of fluid flow in straight nanopores, acoustofluidic physics has attracted great interest in recent decades. Unfortunately, the renewal of the electrolyte concentration at the bottom of a pore is limited. Thus, excitation is used to improve fluid mixing along nanosized diameters. The effect of excitation by high-frequency vibrations on pore geometry is also investigated. In this study, theoretical simulations were performed. Using theoretical calculations, the acoustic pressure, acoustic velocity, and velocity magnitude were obtained at frequencies of 2, 20, and 40 kHz. Moreover, nanoporous AAO membranes were synthesized, and the influence of high-frequency vibrations on the geometry of the pores was determined. Using a high-frequency excitation of 20 kHz, the thickness of the AAO membrane increased by 17.8%. In addition, the thickness increased by 31.1% at 40 kHz and 33.3% at the resonant frequency of 40 kHz. Using high-frequency vibrations during the anodization process, the electrolyte inside the pores is mixed, and as a result, a higher oxide growth rate and a deeper structure can be achieved. On the other hand, to obtain pores of the same depth, the reaction can be performed in a shorter time. Full article
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17 pages, 5583 KiB  
Article
Facile Synthesis of TiO2/MoS2 Composites with Co-Exposed High-Energy Facets for Enhanced Photocatalytic Performance
by Xianjun Niu, Yien Du, Jian Liu, Jinxiao Li, Jiayi Sun and Yuwei Guo
Micromachines 2022, 13(11), 1812; https://doi.org/10.3390/mi13111812 - 24 Oct 2022
Cited by 5 | Viewed by 1270
Abstract
In this work, with the the H2TiO3 colloidal suspension and MoS2 as the precursors, TiO2/MoS2 composites composed of anatase TiO2 nanocrystals with co-exposed {101} and [111]-facets (nanorod and nanocuboid), {101} and {010} facets (nanospindle), and [...] Read more.
In this work, with the the H2TiO3 colloidal suspension and MoS2 as the precursors, TiO2/MoS2 composites composed of anatase TiO2 nanocrystals with co-exposed {101} and [111]-facets (nanorod and nanocuboid), {101} and {010} facets (nanospindle), and MoS2 microspheres constructed by layer-by-layer self-assembly of nanosheets were hydrothermally synthesized under different pH conditions. The characterization has been performed by combining X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectra, and UV-visible absorption spectrum analyses. The photocatalytic degradation of rhodamine B (RhB) in an aqueous suspension was employed to evaluate the photocatalytic activity of the as-prepared pHx-TiO2/MoS2 composites. The photocatalytic degradation efficiency of pH3.5-TiO2/MoS2 composite was the highest (99.70%), which was 11.24, 2.98, 1.48, 1.21, 1.09, 1.03, 1.10, and 1.14 times that of Blank, MoS2, CM-TiO2, pH1.5-TiO2/MoS2, pH5.5-TiO2/MoS2, pH7.5-TiO2/MoS2, pH9.5-TiO2/MoS2, pH11.5-TiO2/MoS2, respectively. The pH3.5-TiO2/MoS2 composite exhibited the highest photocatalytic degradation rate, which may be attributed to the synergistic effects of its large specific surface area, suitable heterojunction structure, and favorable photogenerated charge-separation efficiency. This work is expect to provide primary insights into the photocatalytic effect of TiO2/MoS2 composite with co-exposed high-energy facets, and make a contribution to designing more efficient and stable photocatalysts. Full article
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