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991.
We have investigated oxynitridation of Si(100) surfaces with nitrous oxide (N2O) gas in a wide range of substrate temperatures (600–1000 °C) and N2O pressures (10−2–102 Pa). The growth rate and atomic composition of the oxynitride layer have been measured by in situ x-ray photoelectron spectroscopy. The surface morphology of the oxynitride layer has been also observed by scanning electron microscopy. The results show that in higher N2O pressure (>1 Pa) regime, the nitridation reaction is suppressed by the oxide layer, which quickly forms on the surface. On the other hand, in lower pressure (<1 Pa) and higher substrate temperature (>900 °C) regime, the nitridation reaction strongly occurs because of the active oxidation (etching reaction), which causes the surface roughness. It is found by argon-ion-sputtering measurements that the nitride layer locally exists only near the surface at the reduced N2O pressure. We discuss qualitatively the oxynitridation kinetics and the effective condition for growing the oxynitride layer. 相似文献
992.
Determination of the electrochemical active thickness (EAT) is of paramount importance for optimizing the solid oxide fuel cell (SOFC) electrode. However, very different EAT values are reported in the previous literatures. This paper aims to systematically study the EAT of SOFC anode numerically. An SOFC model coupling electrochemical reactions with transport of gas, electron and ion is developed. The microstructure features of the electrode are modeled based on the percolation theory and coordinate number theory. Parametric analysis is performed to examine the effects of various operating conditions and microstructures on EAT. Results indicate that EAT increases with decreasing exchange current density (or decreasing TPB length) and increasing effective ionic conductivity. In addition to the numerical simulations, theoretical analysis is conducted including various losses in the electrode, which clearly shows that the EAT highly depends on the ratio of concentration related activation loss Ract,con to ohmic loss Rohmic. The theoretical analysis explains very well the different EATs reported in the literature and is different from the common understanding that the EAT is controlled mainly by the ionic conductivity of electrode. 相似文献
993.
Gang Zhao Le Shi Jianbo Xu Xiaohui Yan T.S. Zhao 《International Journal of Hydrogen Energy》2018,43(3):1470-1478
In this paper, we have investigated the role of phosphorus (P) in nitrogen (N) and phosphorus dual-doped carbon electrocatalyst for oxygen reduction reaction (ORR) in alkaline media with three samples prepared by varying the doping orders of N and P. Results show that the resultant N-POMC (first doped with P, then N) exhibits an outstanding activity for ORR in alkaline media. The mechanism leading to the improved activity is found to be associated with the orientation effect of the first doped P on the later doped N, by increasing the ratio of graphitic-N significantly. Furthermore, a portion of the first doped P can act as the doping sites and be replaced by the later doped N, called ‘self-sacrifice’ mode, which is confirmed by both experiments and density functional theory (DFT) calculations. However, this orientation effect cannot be observed in the other two dual-doped samples. In addition, experimental and DFT calculation also prove that the amount of graphitic-N is important in improving the activity for ORR. The doping strategy reported in this work is applicable to various co-doping systems in exploring the synergy effect of different dopants and improving activity for ORR. 相似文献
994.
《International Journal of Hydrogen Energy》2022,47(58):24255-24267
This paper presents hydrogen generation measurements from the hydrolysis of NaBH4 aqueous solutions catalyzed by Co doping on single, bimetallic and trimetallic oxide supports (Co/CuO, Co/NiO, Co/Al2O3, Co/NiO–Al2O3, Co/CuO–Al2O3, and Co/CuO–NiO–Al2O3). Support materials are synthesized by the co-precipitation method. Then, Co is doped into support materials by the impregnation method. It is found that Co/CuO–NiO–Al2O3 catalyst exhibited high reaction activity with a maximum hydrogen generation rate (HGR) of 2067.2 ml min?1 gcat?1 at 25 °C. The effect of temperature of the solution, Co amount, and recyclability of the catalyst on hydrogen generation with Co/CuO–NiO–Al2O3 catalyst is investigated in detail. In addition, the highest HGR for Co/CuO–NiO–Al2O3 catalyst is obtained at 55 °C as 6460.0 ml min?1 gcat?1. The activation energy is calculated to be 31.59 kJ mol?1 using Co/CuO–NiO–Al2O3 catalyst. Co/CuO–NiO–Al2O3 catalyst exhibits zero-order reaction kinetics concerning NaBH4 concentration. In addition, the Co/CuO–NiO–Al2O3 catalyst provided high reusability after 5 cycles. 相似文献
995.
《International Journal of Hydrogen Energy》2022,47(58):24268-24278
In this study, the effect of air addition to the air electrode on the long-term stability and efficiency of solid oxide cells for CO2 electrolysis, with 23.8% CO as protective gas in the fuel electrode, has been investigated. The results show that without continuous purging of the air in the air electrode (Cell-1), the degradation rate was 8.37%/kh in the 1070 h electrolysis process, while with 5 L/min air supplied to the air electrode (Cell-2), the degradation rate was 24.41%/kh. Impedance analysis indicates that the degradation of Cell-1 was mainly because of the increase in O2? exchange polarization impedance, while the degradation of Cell-2 was caused mainly by the variation of ohmic impedance. The microstructural characterization indicated a decrease in active Ni in the fuel electrode in both Cell-1 and Cell-2, but the degree of nickel loss depended on the test time. At the outlet of the Cell-2, the appearance of carbon further explains the faster degradation rate, although the carbon deposition was not directly caused by the introduction of air into the air electrode. Energy spectral analysis shows that the air electrode in Cell-1 generated Sr rich phases, which indicates that the absence of air in the air electrode in the electrolysis process indeed causes more serious microstructure damage. The energy conversion efficiency could exceed 86% if the energy consumed for heating the air is ignored. This work provides a scenario for the application of solid oxide cells for CO2 electrolysis without air purging in the air electrode. 相似文献
996.
《International Journal of Hydrogen Energy》2022,47(63):27166-27176
The maritime industry has entered its pathway of decarbonization. To achieve the IMO's ambitious goals of an absolute emissions reduction of 50% by 2050, and a 70% carbon intensity reduction by 2050 compared to the 2008 level, various options for the adoption of technologies and alternative fuels are considered by the market stakeholders.Ammonia, one of the most promising alternative marine fuels has long been considered to reduce carbon emissions. And solid oxide fuel cell is expected to transform ship propulsion technology in the future due to its high utilization of fuels. In this paper, a feasibility study is performed to assess the application of an ammonia cracker-integrated solid oxide fuel cell (hereafter as Ammonia SOFC) system on an ocean-going vessel through a detailed CAPEX, FuelEX, OPEX, Carbon tax, and carbon emission analysis. Comparison is made with direct ammonia, LNG and conventional fuels fired heat engines. The result concludes that it can be economically viable to apply to deep-sea shipping, compared to other marine fuels and propulsion technologies. 相似文献
997.
《International Journal of Hydrogen Energy》2022,47(16):9735-9743
A new production technique consisting mainly of a combination of tape casting and isostatic pressing to fabricate microtubular supports for solid oxide fuel cells is presented in this study. For this purpose, thin anode support layer is obtained by tape casting. The tape is then wrapped around a rod and subjected to isostatic pressing. The anode support microtube laminate is sintered after the removal of the rod. Microstructural observations show that the anode support with the suggested method is free of delamination and structural defect. Similar microtubular supports are also fabricated by conventional extrusion to compare the mechanical performance. Three point bending test results indicate that the anode supports with the suggested method provide higher mechanical strength due to improved compaction by isostatic pressing. Furthermore, similar microtubular cells are constructed on both anode supports for the electrochemical considerations. The results reveal that the cell, whose anode support is manufactured via tape casting and isostatic pressing, provides a reasonable electrochemical performance although no optimization is carried out in the fabrication steps. Therefore, the method recommended in this study is found to be an appropriate method for the fabrication of tubular/microtubular supports in solid oxide fuel cells or in similar areas. 相似文献
998.
999.
Shun Xu Xuping Lin Ben Ge Desheng Ai Jingtao Ma Zhijian Peng 《International Journal of Applied Ceramic Technology》2019,16(1):108-118
(100-x) wt.% La0.9Sr0.1 Ga0.8Mg0.2O2.85 - x wt.% Ce0.8Gd0.2O1.9 (x = 0, 5, 10, 20) electrolytes were prepared by solid-state reaction. The composition, microstructure, and electrical conductivity of the samples were investigated. At 300 ~ 600°C, the pure La0.9Sr0.1 Ga0.8Mg0.2O2.85 electrolyte has a higher conductivity compared to the composite electrolytes, but at 650 ~ 800°C the 95 wt.% La0.9Sr0.1 Ga0.8Mg0.2O2.85 - 5 wt.% Ce0.8Gd0.2O1.9 composite electrolyte presents the highest conductivity, reaching 0.035 S cm−1 at 800°C. The cell performances based on La0.9Sr0.1 Ga0.8Mg0.2O2.85-Ce0.8Gd0.2O1.9 electrolytes were measured using Sr2CoMoO6-La0.9Sr0.1 Ga0.8Mg0.2O2.85 as anode and Sr2Co0.9Mn0.1NbO6 -La0.9Sr0.1 Ga0.8Mg0.2O2.85 as cathode, respectively. At 800°C, the measured open-circuit voltages are higher than 1.08 V, and the maximum power density and current density of the fuel cell prepared with 95 wt.% La0.9Sr0.1 Ga0.8Mg0.2O2.85 - 5 wt.% Ce0.8Gd0.2O1.9 electrolyte reach 192 mW cm−2 and 720 mA cm−2, respectively. 相似文献
1000.
Zhenwei Wang Haibin Sun Jiao Li Xue Guo Qiangqiang Hu Zanzhong Yang Fangyong Yu Guochang Li 《International Journal of Hydrogen Energy》2021,46(44):22932-22941
Aiming to lower the activation energy and expedite the oxygen reduction reaction (ORR) process of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathodes for application in intermediate-temperature solid oxide fuel cells (IT-SOFCs), Er0.4Bi1.6O3 (ESB) modified LSCF was prepared by infiltrating using organic solvents. The infiltration of ESB dramatically reduces the polarization resistances of LSCF cathodes (from 0.27 to 0.11 Ω cm2 at 700 °C, from 0.58 to 0.25 Ω cm2 at 650 °C), and lowers their activation energy (from 100.28 to 97.15 kJ mol?1). Also, ESB makes the rate-limiting step of LSCF cathodes at high frequency change from the charge transfer process on the cathode to the adsorption and diffusion of oxygen on cathode surface. The single cell with ESB infiltrated LSCF cathodes shows a peak power density of 469 mW cm?2 at 700 °C using humid hydrogen and air as fuels and oxidants, respectively, as well as a good short-term stability for 50 h. 相似文献