New Insights on the Nickel State Deposited by Hydrazine Wet-Chemical Synthesis Route in the Ni/BCY15 Proton-Conducting SOFC Anode

Yttrium-doped barium cerate (BCY15) was used as an anode ceramic matrix for synthesis of the Ni-based cermet anode with application in proton-conducting solid oxide fuel cells (pSOFC). The hydrazine wet-chemical synthesis was developed as an alternative low-cost energy-efficient route that promotes ‘in situ’ introduction of metallic Ni particles in the BCY15 matrix. The focus of this study is a detailed comparative characterization of the nickel state in the Ni/BCY15 cermets obtained in two types of medium, aqueous and anhydrous ethylene glycol environment, performed by a combination of XRD, N2 physisorption, SEM, EPR, XPS, and electrochemical impedance spectroscopy. Obtained results on the effect of the working medium show that ethylene glycol ensures active Ni cermet preparation with well-dispersed nanoscale metal Ni particles and provides a strong interaction between hydrazine-originating metallic Ni and cerium from the BCY15 matrix. The metallic Ni phase in the pSOFC anode is more stable during reoxidation compared to the Ni cermet prepared by the commercial mechanical mixing procedure. These factors contribute toward improvement of the anode’s electrochemical performance in pSOFC, enhanced stability, and a lower degradation rate during operation.

Improved mechanical strength, proton conductivity and power density in an ‘all-protonic’ ceramic fuel cell at intermediate temperature

Protonic ceramic fuel cells (PCFCs) have become the most efficient, clean and cost-effective electrochemical energy conversion devices in recent years. While significant progress has been made in developing proton conducting electrolyte materials, mechanical strength and durability still need to be improved for efficient applications. We report that adding 5 mol% Zn to the Y-doped barium cerate-zirconate perovskite electrolyte material can significantly improve the sintering properties, mechanical strength, durability and performance. Using same proton conducting material in anodes, electrolytes and cathodes to make a strong structural backbone shows clear advantages in mechanical strength over other arrangements with different materials. Rietveld analysis of the X-ray and neutron diffraction data of BaCe0.7Zr0.1Y0.15Zn0.05O3−δ (BCZYZn05) revealed a pure orthorhombic structure belonging to the Pbnm space group. Structural and electrochemical analyses indicate highly dense and high proton conductivity at intermediate temperature (400–700 °C). The anode-supported single cell, NiO-BCZYZn05|BCZYZn05|BSCF-BCZYZn05, demonstrates a peak power density of 872 mW cm−2 at 700 °C which is one of the highest power density in an all-protonic solid oxide fuel cell. This observation represents an important step towards commercially viable SOFC technology.

One-Step Thermal Processing of BaCe0.8Y0.2O3-δ Hydrogen Permeable Multi-Channel Hollow Fiber Membrane

Yttrium-doped barium cerate (BaCeYO, BCY) is the most widely studied proton conducting material and is frequently fabricated as dense membranes for hydrogen separation. However, the difficulty to prepare dense BCY membranes is the extremely high sintering temperature, normally higher than 1500 oC. Herein, the BCY 7-channel hollow fiber membrane was prepared by one-step thermal processing (OSTP). It proved that adding CoO as sintering aid is beneficial to the densification and 1wt% CoO was the optimum addition to form a homogeneous phase structure. The dense sintering temperature was greatly reduced from over 1500 to 1350 C. The hydrogen permeation flux of the BCY hollow fiber membrane reached up to 0.34 ml mincm at 900 C. The long-term stability test last for 300 h. The properties of OSTP samples were demonstrated to be essentially higher than samples made by conventional ceramic hollow fiber fabrication methods.

Nd-Doped Barium Cerate Nano-Sized Catalyst Converts CH4 into CO2 at Lower Temperature Compared to Noble Metal-Based Pd/Al2O3 Catalyst

The present paper describes the synthesis and first application of Nd-doped BaCeO3 nanoparticles as catalyst for the catalytic oxidation of methane (CH4) into CO2. Nd-doped barium cerate BaCeO3 nanoparticles, with the formula BaNdxCe(1-x)O3, have been prepared using a simple sol gel method starting from acetate precursors. The as-prepared nanoparticles have been fully characterized by XRD, TEM, HRTEM and specific surface area measurement. Results confirmed the formation of highly crystallized nano-sized particles with small crystallite size. In-situ FTIR spectroscopy was used to study the catalytic conversion of methane (CH4) into CO2 in the presence of the as-prepared Nd-doped BaCeO3 nanocatalyst. The catalytic properties of such nanocatalysts have been discussed and correlated to Nd-doping rate, crystallite diameter, and specific surface area of the materials. Excellent catalytic properties have been obtained with BaNd0.05Ce0.95O3, such as, superior conversion efficiency, longer catalysis lifetime and lower activation temperature compared to un-doped BaCeO3 catalyst. Interestingly, it was found that BaNd0.05Ce0.95O3 nanocatalyst successfully converts the totality of CH4 present in a mixture of CH4-Air into CO2 at much lower temperature compared to the conventional Pd/Al2O3 catalyst.

Properties of Barium Cerate-Zirconate Thin Films

In this work, we review several experimental results showing the electrical properties of barium cerate-zirconate thin films and discuss them in view of the possible influence of various factors on their properties. Most of the presented Ba(Ce, Zr, Y)O3 thin films were formed by the pulsed laser deposition (PLD) technique, however thin films prepared using other methods, like RF magnetron sputtering, electron-beam deposition, powder aerosol deposition (PAD), atomic layer deposition (ALD) and spray deposition are also reported. The electrical properties of the thin films strongly depend on the film microstructure. The influence of the interface layers, space-charge layers, and strain-modified layers on the total conductivity is also essential but in many cases is weaker.

Improved Mechanical Strength, Proton Conductivity and Power Density in an ‘All-protonic’ Ceramic Fuel Cell at Intermediate Temperature

Protonic ceramic fuel cells (PCFCs) have become the most efficient, clean and cost-effective electrochemical energy conversion devices in recent years. While significant progress has been made in developing proton conducting electrolyte materials, mechanical strength and durability still need to be improved for efficient applications. We report that adding 5 mol% Zn to the Y-doped barium cerate-zirconate perovskite electrolyte material can significantly improve the sintering properties, mechanical strength, durability and performance. Using same proton conducting material in anodes, electrolytes and cathodes to make a strong structural backbone shows clear advantages in mechanical strength over other arrangements with different materials. Rietveld analysis of the X-ray and neutron diffraction data of BaCe0.7Zr0.1Y0.15Zn0.05O3-δ (BCZYZn05) revealed a pure orthorhombic structure belonging to the Pbnm space group. Structural and electrochemical analyses indicate highly dense and high proton conductivity at intermediate temperature (400-700 °C). The anode-supported single cell, NiO-BCZYZn05 | BCZYZn05 | BSCF-BCZYZn05, demonstrates a peak power density of 872 mW cm-2 at 700 °C which is one of the highest power density in an all-protonic solid oxide fuel cell. This observation represents an important step towards commercially viable SOFC technology.

Hydrazine-nitrate combustion synthesis of BaCeO3 preceramic powders: structure, morphology and thermophysical properties

In the present work, preceramic nanocrystallite barium cerate (BaCeO3) was successfully synthesized using the hydrazine-nitrate combustion method. Using carbon-free hydrazine (N2H4) as fuel significantly reduced the formation of carbon by-products. Characterization of the as-received powders was performed by XRD, energy-dispersive X-ray spectroscopy (EDXS), scanning electron microscopy (SEM), simultaneous thermal analysis (DTA-TGA) and adsorption-structural analysis (N2, 77 K). Thermophysical properties of the sample annealed at 1000 °С were investigated using laser flash analysis (LFA) in the temperature interval of 1000 °С. As a result of a comprehensive study, the sequence of chemical and phase transformations that lead to the formation of BaCeO3 with a rhombic structure (Pnma, a = 6.2145 Å, b = 8.7776 Å, c = 6.2337 Å) during the thermal processing of combustion products was investigated. It was established that the average size of the obtained nanocrystals is 38 ± 3 nm and that they form micron-sized agglomerates with a specific surface area of the powder of 4.8 m2/g. It was shown that the sintered sample of BaCeO3 is characterized by thermal diffusivity values of 0.28 to 0.20 mm2/s and thermal conductivity values of 0.41 to 0.35 W/mK, depending on temperature. These results, given the impact of porosity on the sample (~ 40%), show very good agreement with the thermophysical characteristics of densely sintered ceramics based on BaCeO3 – a solid oxide electrolyte SOFC. Consequently, the proposed method of hydrazine-nitrate synthesis of BaCeO3 presents itself as a promising approach to obtaining preceramic powders and ceramics in the area of SOFC.

The Impact of Zr Substitution on the Crystal Structure of Yb Doped BaCeO3 Solid Solution Prepared by a Sol-Gel Method

A modified sol-gel method using metal nitrate salts was adopted to synthesis proton conductor of Ba(Ce1-xZrx)0.95Yb0.05O2.975 where x=0.2, 0.3, 0.4, 0.5 and 0.6 ceramic powders. The aim of this work is to study the crystal structure of Yb-doped barium cerate solid solution at different Zr concentrations. The powder was calcined at 1100°C for 12 hours and pressed at 5 tons to become a pellet by a dry pressing technique. The pellet was sintered at 1400°C in air for 6 hours and ground to powder form prior to the X-ray diffraction measurement. The raw diffraction data of the sample at room temperature was analyzed using Rietveld refinement method in X’pert Highscore software. Cubic crystal structure was observed by software with goodness of fit in average 2.82. Phase formation, structure analysis and the empirical rule which holds the linear relation between lattice parameters at different Zr concentrations using Vegard’s Law were also presented and discussed.