Types Of Energy Conversion Devices Research Articles

Influence of Fe–N–C morphologies on the oxygen reduction reaction in acidic and alkaline media

AbstractThe development of nonnoble metal oxygen reduction reaction (ORR) catalysts for fuel cells has been motivated by the high cost and limited supply of noble metals, as well as the desire to improve the performance and durability of this type of energy conversion device. In this study, nonnoble Fe–N–C catalyst was synthesized using a zeolitic imidazole framework (ZIF‐8), poly (aniline), and 10,10′‐dibromo‐9,9′‐bianthry as precursors to produce Fe–N–C with hollow sphere (HS), amorphous bulky structure (B), and sheet‐like thin sheet (N) structure. The Fe–N–C catalyst was analysed in terms of their shape, crystal structure, pore characteristics, and elemental composition. Among all the Fe–N–C catalysts, Fe–N–C_HS had the highest total surface area, followed by Fe–N–C_B and Fe–N–C_N. To evaluate their ORR catalytic activity, a half‐cell electrochemical experiment with .1 M KOH and .1 M HClO4 as the alkaline and acidic electrolytes was conducted. This study revealed that Fe–N–C_HS exhibited the highest onset potential but the Fe–N–C_B has the highest limiting current density in alkaline medium; meanwhile, in acidic media, Fe–N–C_HS shows the best ORR performance with the highest onset potential and limiting current. This highly porous Fe–N–C_HS catalyst also demonstrated active site activation and excellent stability compared with the other samples as well as commercial Pt/C in acidic electrolyte, which suggests its potential for application in proton exchange membrane fuel cells (PEMFCs).

Improving performance of proton ceramic electrolysis cell perovskite anode by Zn doping

As an important renewable energy, hydrogen energy becomes an important part of the future energy system. Proton ceramic electrolysis cell (PCEC) enables the efficient, clean, large-scale preparation of hydrogen, which is a new type of energy conversion device, attracting the attention of many researchers. Sr2Fe1.4Zn0.1Mo0.5O6-δ (SFZM) anode materials were developed to investigate the effect of B-site doping of Zn on the electrochemical properties of the Sr2Fe1.5Mo0.5O6-δ (SFM) materials. The results reveal that the doping of Zn increases the concentration of oxygen vacancies and improves the electrocatalytic activity, which in turn improves the performance of the material. A current density of 408 mA cm−2 has been achieved at 1.3 V when the SFZM-based single cell was operated in an electrolysis mode (50% H2O in air) at 600 °C, higher than SFM-based single cells (286 mA cm−2 at 1.3 V). In addition, the SFZM-based single cell exhibited good durability in a stability test at an electrolysis current density of 408 mA cm−2. This work confirms that SFZM is a promising material for proton ceramic electrolysis cell anode.

La1-xCaxFeO3-δ air electrode fabricated by glycine-nitrate combustion method for solid oxide electrolysis cell

As a new type of energy conversion device, solid oxide electrolysis cell (SOEC) has attracted much attention in recent years because of its advantages such as high efficiency and unlimited capacity. At present, SOEC mainly has such issues as the element diffusion or delamination at oxygen electrode/electrolyte interface under high oxygen partial pressure, which limits its operation lifetime. In this paper, La1-xCaxFeO3-δ materials without Sr and Co were prepared by glycine-nitrate combustion method as SOEC oxygen electrodes. It is found that La0.6Ca0.4FeO3-δ (LCF64) has excellent electrical conductivity and has a coefficient of thermal expansion matching with SSZ electrolyte. The hydrogen electrode supported single cells with structure of LCF64-GDC (6:4) | GDC | SSZ | NiO-SSZ active layer | NiO-YSZ transition layer | NiO-YSZ supported layer were prepared by tape casting and co-firing method showed good electrochemical performance in SOEC mode. The electrolysis current density is 457.46 mA cm-2 with 60% H2O-H2 atmosphere and 1.3 V applied voltage at 800 °C. During the constant voltage (1.3V) electrolysis process, the SOEC showed an acceptable stable current density of approximate 280 mA cm-2 for more than 60 h.

Studies of electrical and optical properties of cadmium‐doped zinc oxide for energy conversion devices

AbstractIn this modern era, energy devices have become an important part of our daily life. Various types of energy conversion devices have been developed to meet the current energy demands. Semiconductor anode (CdZnO) has been synthesized by the sol‐gel method and lattice constants and the band gap results have been compared experimentally and theoretically. XRD results show that Cd‐doped ZnO shifts the peaks toward the lower angles, increases the lattice parameters, and decreases the crystallite size (48 nm). Microstructure of Cd‐doped ZnO shows the agglomerations of particles, found in the shape of cubes, hexagons, and dumbbell shapes with diameter in the range of 2–7 µm. The experimentally obtained conductivity of CdZnO is 0.142 S/cm at 550°C. The electrochemical impedance spectroscopy shows the decreased resistance with an increase in temperature. The doped system shows a maximum open circuit voltage of 0.95 V and performance of 0.52 W/cm2 at 550°C.

Electrochemical Impedance Analysis of Thermogalvanic Cells

Thermogalvanic cells(also known as thermo-electrochemical cells) that convert waste heat energy to electricity are a new type of energy conversion device. However, the electron transfer kinetics and mass transfer of redox couples have not been thoroughly studied. Here, the ion reaction and charge transport in thermogalvanic cells are investigated by electrochemical impedance analysis. We first propose the detailed impedance model followed experimental verification on three types of electrode materials. Parameters including kinetic rate constants and ion diffusion coefficients for the electrodes are obtained by fitting the impedance data. Our study shows explicitly that impedance analysis can provide useful information on selecting suitable electrode materials for thermogalvanic cells.

(Invited) Ordered Semiconductor Through-Hole Membranes with Controlled Geometrical Structures by Anodization Processes

The semiconductor materials with naturally occurring self-ordered nanostructures have attracted growing interest for the preparation of functional nanodevices for energy conversion.1 To obtain the nanodevices with optimized performance, control of the geometrical structure of semiconductors is essential. For example, the fabrication of highly ordered structures of semiconductors contributes to the efficient absorption of the incident light and also enhance the charge separation in the interfaces. Anodization process of metals is an effective method for the preparation of ordered hole array structures of metal oxides. One advantageous point of this process is controllability of the geometrical structures of the obtained porous structures based on the anodization conditions.2 In addition, the naturally occurring self-ordered ordered nanoporous structures can be obtained under the appropriate anodization conditions. In our previous reports, we described that ordered nanothrough-hole membranes can also be obtained effectively by two-layer anodization process.3,4 This process allows repeated preparation of ordered through-hole membranes from a single metal substrate by repetition of the process. As an application to semiconductor through-hole membranes, ordered TiO2 through-hole membranes were obtained by two-layer anodization using an electrolyte containing fluoride ions.5 The hole period of the obtained TiO2 membranes could be controlled by changing the anodizing voltage. In the present report, preparation of various types of semiconductor through-hole membranes will be presented. For example, the preparation of ideally ordered TiO2 through-hole membranes by the combination process of two-layer anodization and pretexturing of Ti was described. The obtained TiO2 through-hole membranes with controlled geometrical structures will be applied to various types of energy conversion devices. 1. P. Roy, S. Berger, P. Schmuki, Angew. Chem. Int. Ed., 50, 2904 (2011).2. H. Masuda and K. Fukuda, Science, 268, 1466 (1995).3. T. Yanagishita and H. Masuda, Electrochim. Acta, 184, 80 (2015).4. T. Yanagishita, A. Kato, T. Kondo, and H. Masuda, Jpn. J. Appl. Phys., 56, 035202 (2017).5. T. Yanagishita, H. Inada, T. Kondo, N. T. Nguyen, P. Schmuki, and H. Masuda, J. Electrochem. Soc., 165, E763 (2018).

(Invited) Ordered Nanoporous Semiconductors with Controlled Geometrical Structures By Anodization Processes

For the preparation of functional nanodevices for efficient energy conversion, the use of the naturally occurring self-ordered structures is considered an effective process due to its capability of formation of precisely controlled fine nanostructures. To optimize the performance of the obtained devices, fabrication of precisely controlled geometrical structures of metals and semiconductors is essential. For example, the fabrication of highly ordered structures of metal and semiconductors contributes to the efficient absorption of the incident light and also enhance the charge separation in the interfaces. The anodization processes of metals have been widely applied to the fabrication of nanostructures of metal oxides. One advantageous point of this process is controllability of the geometrical structures of the obtained porous structures based on the anodization conditions. In addition, the ordered nanoporous structures can be obtained under the appropriate anodization conditions. In the present report, recent results concerning the preparation of nanoporous semiconductors with controlled geometrical structures and its applications are described. As a typical example, naturally ordered processes1 or pretexturing process2were applied to the preparation of nanoporous TiO2 with controlled geometrical structures. In addition, a high through-put process for the preparation of the through-hole membrane of TiO2 was also described. This process is based on the two-layer anodization used for the preparation of porous alumina through hole membranes3. The tow-layer anodization, which generates TiO2 layers with different solubility, and subsequent selective dissolution generate the through hole membrane of TiO2 4. Repetition of the process allows the high-throughput preparation of the ordered TiO2 through hole membranes. In addition to the self-ordered TiO2, preparation of the ideally ordered TiO2 through hole membranes is demonstrated. The obtained TiO2 through-hole membranes with controlled geometrical structures will be applied to various types of energy conversion devices. P. Roy, S. Berger, P. Schmuki, Angew. Chem. Int. Ed., 50, 2904 (2011).T. Kondo, S. Nagao, T. Yanagishita, N. T. Nguyen, K. Lee, P. Schmuki, H. Masuda, Electrochem. Commun., 50, 73 (2014).T. Yanagishita and H. Masuda, Electrochim. Acta, 184, 80 (2015).T. Yanagishita, H. Inada, T. Kondo, N. T. Nguyen, P. Schmuki, and H. Masuda, J. Electrochem. Soc., 165, E763 (2018).

Gas Humidification Impact on the Properties and Performance of Perovskite‐Type Functional Materials in Proton‐Conducting Solid Oxide Cells

AbstractFuel cells and electrolysis cells as important types of energy conversion devices can be divided into groups based on the electrolyte material. However, solid oxide cells (SOCs) based on conventional oxygen‐ion conductors are limited by several issues, such as high operating temperature, the difficulty of hydrogen purification from water, and inferior stability. To avoid these problems, proton‐conducting oxides are proposed as electrolytes for SOCs in electrolysis and fuel cell modes. Since water vapor partial pressure (pH2O) is one of the main parameters determining the proton concentration in proton‐conducting oxides (characteristics of which can be either improved or deteriorated), the pH2O control is extremely important for the optimization of the devices' performance and stability. This review provides an overview of the research progresses made for proton‐conducting SOCs, especially for the impact of gas humidification on the operability and performance. Fundamental understanding of the main processes in proton‐conducting SOCs and design principles for the key components are summarized and discussed. The trends, challenges, and future directions that exist in this dynamic field are also pointed out. This review will inspire interest from various disciplines and provide some useful guidelines for future development of proton‐conductor‐based energy storage and conversion systems.

Atomic layer deposition, a unique method for the preparation of energy conversion devices.

Keywords: atomic layer deposition; batteries; energy conversion; electrochemistry; electrolysis; fuel cells; photovoltaics; solar cells; thin films

Functional mesoporous materials for energy applications: solar cells, fuel cells, and batteries

This feature article presents recent progress made in the synthesis of functional ordered mesoporous materials and their application as high performance electrodes in dye-sensitized solar cells (DSCs) and quantum dot-sensitized solar cells (QDSCs), fuel cells, and Li-ion batteries. Ordered mesoporous materials have been mainly synthesized using two representative synthetic methods: the soft template and hard template methods. To overcome the limitations of these two methods, a new method called CASH was suggested. The CASH method combines the advantages of the soft and hard template methods by employing a diblock copolymer, PI-b-PEO, which contains a hydrophilic block and an sp(2)-hybridized-carbon-containing hydrophobic block as a structure-directing agent. After discussing general techniques used in the synthesis of mesoporous materials, this article presents recent applications of mesoporous materials as electrodes in DSCs and QDSCs, fuel cells, and Li-ion batteries. The role of material properties and mesostructures in device performance is discussed in each case. The developed soft and hard template methods, along with the CASH method, allow control of the pore size, wall composition, and pore structure, providing insight into material design and optimization for better electrode performances in these types of energy conversion devices. This paper concludes with an outlook on future research directions to enable breakthroughs and overcome current limitations in this field.