The development of high performance, stable catalyst with non-precious metals for electrochemical hydrogen evolution reaction for alkaline electrolysis is in demand. Here-in, we report the synthesis ...of CuFe layered double hydroxide (LDH) electrocatalyst on nickel foam via facile hydrothermal method. In alkaline electrolysis with 1 M NaOH electrolyte, CuFe LDH as cathode requires an overpotential of 159 mV to generate current density of 10 mA cm−2. Which is ca. 51 mV and 7 mV lower than NiFe LDH and NiRu LDH. CuFe LDH exhibits significant electrocatalytic activity for HER. The higher catalytic activity of CuFe LDH compared to NiFe LDH may be achieved with higher proton adsorption by Cu compared to Ni. Also, the efficient charge transfer with interconnected LDH layers, favourable three dimensional structure facilitating easy electrolyte transfer to the active sites and hydrogen gas diffusion. This work may help in developing low cost and efficient hydroxide catalyst.
•CuFe layered double hydroxide is prepared by hydrothermal process.•Synthesis of low cost and non-precious metal electrocatalyst for electrolysis.•CuFe LDH/Ni electrocatalyst requires only 159 mV at 10 mA cm−2 in HER.•Stable after 5 h chronopotentiometry test.
Summary
Recently, highly porous metal foams have been used to replace the traditional open‐flow channels to improve gas transport and distribution in the cells. Deformation of flow plate, gas ...diffusion layer (GDL), and metal foam may occur during assembling. When the cell size is small, the deformation may not be significant. For large area cells, the deformation may become significant to affect the cell performance. In this study, an assembling device that is capable of applying uniform clamping force is built to facilitate fuel cell assembling and alleviate the deformation. A compressing plate that is the same size of the active area is used to apply uniform clamping force before surrounding bolts are fastened. Therefore, bending of the flow plate and deformation of GDL and metal foam can be minimized. Effects of the clamping force on the microstructures of GDL and metal foam, various resistances, pressure drops, and cell performance are investigated. Distribution of the contact pressure between metal foam and GDL is measured by using pressure sensitive films. Field‐emission scanning electron microscope is used to observe the microstructures. Electrochemical impedance spectroscopy analysis is used measure resistances. The fuel cell performance is measured by using a fuel cell test system. For the cell design used in this study, the optimum clamping force is found to be 200 kgf. Using this optimum clamping force, the cell performance can be enhanced by 50%, as compared with that of the cell assembled without using clamping plates. With appropriate clamping force, the compression force distribution across the entire cell area can approach uniform. This enables uniform flow distribution and reduces mass transfer resistance. Good contact between GDL and metal foam also lowers the interface resistance. All these factors contribute to the enhanced cell performance.
An assembling device capable of applying uniform clamping force is built to facilitate fuel cell assembling and maintain the flow field uniformity.
With the optimum clamping force of 200 kgf, the cell performance is enhanced by 50%, due to reduced mass transfer resistance and interface resistance provided by the resultant uniform compression pressure distribution.
This research aims to develop a better carbon resistant anode compared to conventional Ni-BCZY anode for methane fueled protonic ceramic fuel cell (PCFC). Solid-state reaction process is used to ...prepare alloy Ni1-xCux-BCZY anode in PCFC. Ni is doped with Cu for better carbon resistance. Results show that, Ni0·9Cu0.1-BCZY anode calcined at 800 °C for 0.5 h exhibit an electrical conductivity of 2054 S/cm at 600 °C, which is 8.4% less than traditional Ni-BCZY anode. XPS, and Raman data show that Ni0·9Cu0.1-BCZY anode exhibit resistance to carbon deposition compared to traditional anode. The best carbon deposition resistance is observed for the Ni0·7Cu0.3-BCZY sample. This work demonstrates the suppression of carbon deposition and inhibition of anode deformation in methane fueled PCFC with Ni1-xCux-BCZY anode. This work is helpful for development of carbon-resistant materials for energy generation with solid oxide fuel cells.
•Cu is doped in Ni-BCZY anode for increasing carbon deposition resistance (CDR).•Effects of Cu content on CDR and conductivity of anode are investigated.•EDS, XPS, EA and Raman spectroscopy are used to characterize CDR.•Increasing Cu content increases CDR, but reduces conductivity.
A thin and fully dense BaCe0.6Zr0.2Y0.2O3-δ (BCZY) electrolyte for the use of anode-supported protonic fuel cells has been successfully prepared by spin coating using NiO sintering aid. The effects ...of NiO addition on the electrolyte microstructures and fuel cell performances are also investigated. An appropriate NiO addition has a significant positive contribution to the densification and grain growth of thin BCZY electrolytes. However, too much NiO addition gives rise to NiO aggregation in BCZY electrolyte and deteriorates the cell performance. The enhanced sintering mechanism can be mainly attributed to the oxygen vacancies generated from the NiO decomposition and bulk diffusion of Ni into BCZY perovskites. The fuel cell with a BCZY-3%NiO electrolyte exhibits the highest maximum power density of ~106.6 mW/cm2 at 800 °C among all fuel cells in this study. The electrochemical impedance characteristics of thin BCZY electrolyte fuel cells are further discussed under open circuit conditions.
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•A thin BCZY electrolyte has been prepared by spin coating using NiO sintering aid.•The enhanced sintering mechanism can be attributed to increased oxygen vacancies.•An appropriate NiO addition promotes the BCZY densification and grain growth.•Too much NiO addition gives rise to NiO aggregation in BCZY electrolyte.•The cell with a BCZY-3%NiO electrolyte exhibits the highest peak power density.
In this work, we vary the Zr to Ce ratio to investigate the microstructures and electrical properties of zirconium doped barium cerates. The solid state reaction is used in synthesizing the ...BaCe0.8-xZrxY0.2O3 (X = 0.1–0.5). The electron backscatter diffraction (EBSD) is successfully applied to identify the crystal structure of the barium cerates. EBSD results indicate that all samples have the orthorhombic structure. Conductivity measurement results show that for temperatures below 700 °C, Zr-doped barium cerates have higher protonic conductivities than oxygen-ion/electron-hole conductivities. The protonic conductivity increases with the Zr content initially, but decreases after the Zr content is higher than 0.3. The protonic conductivity of BCZY0.3 reaches 8.8 mS/cm at 700 °C in dry hydrogen atmosphere. Stability test results show that, for stable operation in CO2 atmosphere, the Zr content in barium cerates should be greater than 0.2.
•EBSD is used to find orthorhombic structure predominates in BCZY.•Protonic conductivity is much higher than oxygen ion conductivity for T < 700 °C.•The Zr ratio of 0.3 sample has the highest protonic conductivity.•The protonic conductivity BCZY0.3 sample reaches 8.8 mS/cm at 700 °C.•Zr ratio of >0.2 gives good CO2 stability.
To obtain dense, high-quality electrolytes, sintering of the proton-conducting electrolyte BaCe0.6Zr0.2Y0.2O3 (BCZY) in protonic ceramic fuel cells (PCFCs) should be conducted at relatively high ...temperatures. However, in the co-sintering of a porous anode substrate and electrolyte thin film, high sintering temperatures often cause the coarsening of the NiO-BCZY anode, thus reducing the number of electrocatalytic active sites for H2 oxidation as well as degrading cell performance. A scalable nanomilling process is proposed to reduce electrolyte sintering temperature to maintain triple phase boundary, good electron and proton transport in PCFC anode. By using the nanomilling process, BCZY nanoparticles more than halved the original diameter (from 297 nm to 131 nm) were produced. The co-sintering temperature can be lowered. The cell sintered at 1400 °C exhibited the highest peak power density of 490 mW/cm2, 38% higher than that of un-nanomilled process. The substantial improvement in cell performance can be attributed to the lower co-sintering temperature, which caused less coarsening of the NiO anode. This preserved a greater number of electrocatalytic active sites for H2 oxidation by Ni in cell operation, as evidenced by the 50% decrease in charge transfer resistance from electrochemical impedance measurements.
The performance of a high temperature proton exchange membrane fuel cell (HT-PEMFC) with metal foam as the flow field is investigated. The HT-PEMFC is assembled using commercial membrane electrode ...assembly, Advent TPS® HT PEM MEA. In addition to metal foam flow field, conventional graphite serpentine flow is also used to assemble a single cell using the same MEA for comparison. Effects of operating temperature, stoichiometry, gas preheating temperature, and humidification on cell performance are investigated. AC impedance analysis is also used to study the changes in various resistances and electrochemical mechanisms inside the cell.
Results show that metal foam flow field, having high gas permeability, improves gas convection and diffusion, and increases the chance of reaction with the catalysts. The porous structure of metal foam can effectively reduce the contact resistance between the flow plate and carbon paper. The current density at 0.6 V of metal foam fuel cell is approximately 20% higher than conventional graphite serpentine flow channel fuel cell. Increasing the operating temperature, stoichiometry, or humidification, improves the cell performance. Initial 300 h operation test shows the cell is relatively stable.
•Metal foam flow field is applied to HT-PEM fuel cell.•Metal foam cell's performance is 20% better than conventional cell.•Low air stoichiometry suffices for stable operation.•Effects of operating parameters are investigated.
Low-temperature solid oxide fuel cells (LT-SOFCs) have recently gained enormous attention worldwide with a new research trend focusing on single layer fuel cells (SLFC), which have better cell ...performance than traditional SOFCs at low operating temperatures. In this study, a triple (e−/O2−/H+) conducting perovskite BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) is used as the intermediate layer material for SLFC. A high current density of 994 mA/cm2 at 0.6 V and a peak power density of 610 mW/cm2 with an OCV of 1.01 V has been achieved with a cell operating temperature of 550 °C, confirming the application feasibility of BCFZY in SLFCs. Furthermore, a typical proton conductor BaZr0.8Y0.2O3-δ (BZY) is introduced into BCFZY to enhance the cell performance. By adjusting the mass ratio of the BCFZY-BZY layer, an optimal power density is obtained, achieving 703 mW/cm2 with an OCV of 1.03 V at 550 °C with an 8BCFZY:2BZY (wt%) ratio. These findings prove that the proposed BCFZY-BZY holds great promise for developing SLFCs to realize low-temperature operation.
•A triple conducting BaCo0.4Fe0.4Zr0.1Y0.1O3-δ is applied in single layer fuel cell.•The peak power density of SLFC with pure BCFZY reaches 610 mW/cm2 at 550 °C.•BaZr0.8Y0.2O3-δ (BZY) is used to optimize the mixed conductivity.•With 20% BZY, the peak power density rises to 703 mW/cm2 at 550 °C.
In this study, we investigate the effects of adding titanium dioxide (TiO2) and samarium doped cerium oxide (SDC) on the properties of yttrium-stabilized zirconia (YSZ) electrolyte. The ...microstructure, mechanical, and electrochemical properties of the electrolyte are investigated. The performance in CO2 electrolysis is measured by supplying carbon dioxide to Ni-YSZ electrode and nitrogen to LSM electrode. Results show that TiO2 and SDC addition can reduce the sintering temperature and increase grain size. The ionic conductivity is 0.123 S cm−1 at 1000 °C. In addition, the thermal expansion coefficient at 1000 °C is 8.25 × 10−6 K−1. The current density of the cell is 439 mA cm−2 at 1.3 V and 1000 °C in solid oxide electrolysis cell.
•Effects of SDC and TiO2 doping on YSZ properties are investigated.•TiO2 and SDC addition reduces the sintering temperature and increases grain size.•TiO2 and SDC addition increases conductivity to 0.123 S cm−1 at 1000 °C.•An LSM/3TiYSZ-SDC/Ni-YSZ single cell is successfully assembled.•The CO2 electrolysis current density reached 439 mA/cm2 at 1.3 V.
Utilization of 500-nm-diameter polystyrene (PS) nanospheres as pore former in a screen printing process to tailor the porous structure of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode for improving the ...performance of protonic solid oxide fuel cells is reported. The effects of PS nanosphere amount on cathode microstructure and cell performance are investigated. It is found that PS nanospheres can undergo a self-organized distribution in the screen-printed LSCF cathode due to the large difference in density between PS and LSCF, resulting in a porosity gradient in the cathode structure. The fuel cell with a 15 wt% PS-tailored cathode exhibits a much higher power density compared to that without tailoring by PS. The enhanced cell performance can be ascribed to the graded porosity in the cathode structure, which significantly reduces the ohmic and polarization resistances. It seems that such a graded-porosity cathode structure not only facilitates the generation and migration of O−ad from catalytic sites to triple phase boundaries (TPBs) but also promotes transfer of protons from the electrolyte to the TPBs.
