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    25 August 2022, Volume 44 Issue 8
    Cell System with Oxygen-Ion Conducting Electrolyte
    Progress in technologies of metal-supported solid oxide fuel cells
    GAO Yuan, LI Zhi, LI Jiahong, GAO Jiutao, LI Chengxin, LI Changjiu
    2022, 44(8):  1-24.  doi:10.3969/j.issn.2097-0706.2022.08.001
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    Metal-supported solid oxide fuel cell (MS-SOFC), being able to start-up rapidly, are transformative technology to facilitate the realization of dual carbon target. With low-cost ferritic stainless steel as support whose thermal expansion coefficient(CTE) is similar to that of ceramic electrolyte, MS-SOFC is expected to be of a significantly lower manufacturing cost, good mechanical performance and sealing performance. Metal interconnect and metal support are two core components for a MS-SOFC, and their common materials are ferritic stainless steel, Cr-based alloy and Ni-based alloy. Japan, Germany, the United States and China have developed various stainless steels for SOFCs. And stainless-steel coating technologies have made significant progress which can improve the high temperature oxidation resistance of the materials. In view of the problem in the MS-SOFC prepared by high-temperature sintering method, thermal spraying method and low-temperature sintering method have taken its place. The metal support and interconnect of a MS-SOFC can be effectively connected by traditional welding method, and the fuel gas can be effectively sealed by taking porous metal support-connector structure which is formed in powder pressing and sintering processes. The reasons for the degradation of MS-SOFCs include oxidation of metal materials, cathodic toxicity caused by Cr volatilization, coarsening of catalyst particles,etc. Many companies, such as Ceres Power of the UK, General Electric(GE) of the US, German Aerospace Center(DLR), German Forschungszentrum Jülich(FZJ) and Plansee of Austria, have made remarkable achievements in preliminary commercialization of MS-SOFC.

    Design of the CHP system integrated with SOFC
    LUO Liqi, WANG Yue, ZHONG Haijun, LI Qingxun, XIE Guangyuan, WANG Shaorong
    2022, 44(8):  25-32.  doi:10.3969/j.issn.2097-0706.2022.08.002
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    The software Aspen Plus is taken to simulate a combined heating and power system integrated with solid oxide fuel cells(SOFC-CHP). Taking a 1 kW SOFC-CHP system as an example,the simulation method can make quick judgement on the heat and power supply situations of the system with different fuels and under various load requirements. The test results show that in the ideal condition,the power generation efficiency of the SOFC can reach 51%,the thermal efficiency can peak at 42%,and the emitted CO2 mole fraction can be 70%. This method can greatly shorten the calculation time and facilitate the efficiency improvement of the system.

    Application of alloy nanoparticles in the anodes of hydrocarbon solid oxide fuel cells
    ZHU Shasha, LI Zongbao, DENG Yatian, WANG Xin, JIA Lichao
    2022, 44(8):  33-42.  doi:10.3969/j.issn.2097-0706.2022.08.003
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    Alloy nanoparticles(NPs)have been widely used in the anodes of solid oxide fuel cells (SOFCs) because of their excellent catalytic performances and high resistances to coke deposition and H2S. These unique properties mainly originate from the synergistic effect between different metals. In-situ preparation of NPs from parent oxides in reducing atmosphere can produce supported metal nanoparticles with high stability and parent oxides with high oxygen vacancies, which improves the electronic and ionic conductivities of anodes. The excellent catalytic performance of alloy catalysts makes it possible for SOFCs to take hydrocarbon as fuel and operate stably and durably. The trends and advances in metal alloy nanoparticles applied to the anodes of SOFCs are summarized and the prospects for further studies in this field are proposed.

    Study on La/Ni co-doped SrTi0.35Fe0.65O3-δ symmetric electrode for H2O/CO2 co-electrolysis in SOECs
    HAN Qianwen, ZHANG Kun, CHEN Xiaoyang, ZHU Tenglong
    2022, 44(8):  43-47.  doi:10.3969/j.issn.2097-0706.2022.08.004
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    Hydrogen production from water steam electrolysis powered by solid oxide electrolysis cells (SOECs) and syngas production by co-electrolysis of H2O/CO2 are important routes to promote the application of renewable energy and development of green and low-carbon chemical industry. To meet the demands for high performance and stable operation of SOECs,La/Ni co-doped SrTi0.35Fe0.65O3-δ strategy was adopted,and La0.1Sr0.85Ti0.35Fe0.6Ni0.05O3 (LSTFN) was designed and prepared as both hydrogen and oxygen electrodes for SOECs. The structural composition and micromorphological evolution of LSTFN electrode were investigated by scanning electron microscopy(SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The H2O/CO2 co-electrolysis performance and reversible operation stability were examined. The results show that, Ni-Fe alloy nanoparticles in-situ precipitated on LSTFN hydrogen electrode surface are stable in complex steam and carbon-containing atmospheres. The LSTFN co-electrolysis current reaches 1.8 A/cm2 in 800 ℃,1.8 V and 10% H2 protective atmosphere(H2/H2O/CO2=10∶45∶45). LSTFN symmetric cell performs stably in reversible operations between power generation and co-electrolysis, showing good application prospects.

    Research progress on preparation methods of medium and low temperature SOFC electrolytes
    YANG Ying, ZHANG Yanxiang, YAN Mufu
    2022, 44(8):  50-57.  doi:10.3969/j.issn.2097-0706.2022.08.005
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    Solid oxide fuel cells (SOFCs) can convert chemical energy into electric energy through the electrochemical reaction between hydrogen and oxygen, which is in line with the clean and low carbon orientation and is conducive to the realization of dual carbon target. Reducing the thickness of the electrolytes is beneficial for lowering the operating temperature of conventional SOFCs and improving their electrochemical performances in medium and low temperatures (< 600 ℃). The main process characteristics and research progress of several typical electrolyte preparation techniques are reviewed, and their advantages and limitations of electrolytes' industrial production are analysed.It is pointed out that physical vapor deposition represented by pulsed laser deposition and magnetron sputtering is more in line with the concept of clean production and more suitable for industrial production.

    Cell System with Proton Conducting Electrolyte
    Review on the study of protonic ceramic fuel cells' stability
    CAO Jiafeng, LI Xinran, SHAO Shande, JI Yuexia, SHAO Zongping
    2022, 44(8):  58-67.  doi:10.3969/j.issn.2097-0706.2022.08.006
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    Protonic ceramic fuel cells (PCFCs) can work in low temperatures and efficiently utilize and store hydrogen energy. But their commercial application is hampered by the poor battery stability.Under current stage, many PCFC present inferior long-term stability while presenting excellent activity. This study emphasizes on the significance of PCFCs' stability in academic researches and practical applications. The intrinsic factors influencing the stability of the key components of PCFCs, electrolytes and electrodes,were expounded based on their material analyses. The analyses point out that the key to the breakthroughs of batteries' performances lay in improving the stability of the electrolyte and electrode materials. This work will be helpful for exploring the fundamental reasons for the cells' degeneration and provide more reliable references from cell stability improvement in engineering cases.

    Development and challenges of intermediate-temperature proton-conducting solid oxide fuel cells
    XU Yangsen, ZHANG Lei, BI Lei
    2022, 44(8):  68-74.  doi:10.3969/j.issn.2097-0706.2022.08.007
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    Proton-conducting solid oxide fuel cells (H-SOFC)are efficient and clean energy conversion devices which can directly convert fuel gas into electric power.Although the preparation technology of traditional fuel cells is mature,its development is dramatically limited by high working temperatures.As the working temperature of fuel cells get decline,intermediate-temperature proton-conducting fuel cells attract extensive attention of researchers.H-SOFC are of the advantages of traditional fuel cells such as all-solid state and flexible application,and also show excellent electrochemical performances.However,the slow kinetics of the cathode reaction and the decrease of proton conductivity in low temperature greatly detriment their electrochemical performance.Based on the understanding on the structure and working principle of intermediate-temperature proton-conducting fuel cells,the developments of their electrolytes,anodes and cathodes in recent years are reviewed and the challenges in front of the cells are analyzed.

    Research progress of hydrogen production from water electrolysis in proton-conducting solid electrolytic cells
    CHEN Hanyu, ZHOU Xiaoliang, LIU Limin, QIAN Xinyuan, WANG Zhou, HE Feifan, SHENG Yang
    2022, 44(8):  75-85.  doi:10.3969/j.issn.2097-0706.2022.08.008
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    Since traditional fossil fuels,such as nature gas,coal and petrol oil,have brought energy crisis and environment pollutant to our society, renewable energy becomes the solution to realization "dual carbon" goals. Hydrogen energy attracts much attention because of its high energy density, high efficiency and environmental protection. Hydrogen production from water electrolysis is of simple operation process and high purity product. Hydrogen production technology in solid oxide electrolytic cells(SOECs) powered by new energy attract much attention because of its high efficiency and low environment impact. Compared to the traditional oxygen-ion solid oxide electrolysis cells(O-SOECs)whose development is hampered by narrow operation temperature range,proton-conducting solid oxide electrolysis cells(H-SOECs)are of better performances. Based on the summary on the materials applied to the electrolyte, hydrogen electrodes and air electrodes of H-SOECs, the efficiency of different hydrogen production by water electrolysis technologies and the factors affecting their electrolysis are analyzed. Based on the research progress made on H-SOECs, the existing problems and challenges of the technologies are proposed.

    Preparation and performance study of tubular protonic ceramic fuel cells
    YAN Xueling, PAN Xiang, REN Keke, HUANG Rong, CHENG Jigui, HONG Tao
    2022, 44(8):  86-90.  doi:10.3969/j.issn.2097-0706.2022.08.009
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    Proton ceramic fuel cells (PCFCs) attract great attention for being of lower operating temperatures than solid oxide fuel cells.Furthermore,tubular PCFCs are of higher power density and higher mechanical strength compared with planar PCFCs.To simplify the preparation of large-size tubular PCFCs,hollow glass tubes with tiny pores at their tops are taken as the preparation mold for the anode supporting layers,and the NiO-BaCe0.7Zr0.1Y0.1Yb0.1O3(BCZYYb) anode support is made from raw material powder by one-step preparation based on phase inversion mechanism.To reduce the impact of the ceramic substrates on the tubular PCFC electrolyte ceramic films,various sintering methods are explored.The scanning electron microscope(SEM) image of an anode support after high-temperature co-sintering presents that there are a large number of connected pores in the anode support.Dip-coating method provide the anode support with a 30 μm dense BZCYYb electrolyte layer.At 600 ℃,the power density of the tubular PCFC with humid hydrogen as fuel and ambient air as oxidant can peak at 80 mW/cm2,and the ohmic resistance and polarization resistance can reach 14 Ω·cm2 and 16 Ω·cm2,respectively.The one-step preparation method integrated phase inversion mechanism and solid reaction sintering can make tubular PCFCs from raw materials powder,which can be applied to large-scale tubular PCFC production.

    Technology Exchange
    Simulation and optimization for the PEMFC based on single-cell stack structure
    HU Chong, ZHAO Yuan, RAZA Ali, CHEN Daifen
    2022, 44(8):  91-96.  doi:10.3969/j.issn.2097-0706.2022.08.010
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    Proton exchange membrane fuel cells(PEMFCs) attract extensive attention due to their high power-generation efficiency and working stability at normal temperatures. Traditional PEMFCs are vulnerable to flooding because of the uneven power generation loads among stacks. Most researches on PEMFC optimization are made by improving the flow field of a single cell, but PEMFCs are usually assembled in the form of stacks. Thus, a single-cell stack structure with a vertical channel as the inlet and outlet of reactants is designed, and a new series compensation flow field is proposed which has three air inlets and three flow channels connected in series. Reactants can compensate each other in the flow channel. A simulation study is conducted on the singe-layer PEMFC stack by ANSYS. On the premises that the anode adopts the same serpentine flow field and the cathode adopts the traditional single-channel serpentine flow field or the new series compensation flow field, the distributions of current density, oxygen mass fraction, liquid water saturation, velocity vector and flow channel pressure in the porous medium layers(GDL and CL) of the singe-layer PEMFC stack are analyzed. The simulation results show that the single-layer PEMFC stack in traditional single-channel serpentine flow field is of a higher overall channel pressure, and the closer it is to the inlet, the higher the current density and oxygen mass fraction are, and vice versa. The liquid water saturation around the outlet is relatively high and the velocity vector shows no significant increase as liquid water tends to hoard around the outlet. However, the current density distribution in the new series compensation flow field is relatively even, and there are multiple and extensive-distributed areas with high oxygen mass fractions. The electrochemical reaction is more sufficient and the overall pressure drop is lower. The velocity vector is significantly higher in the areas with higher oxygen mass fraction, which promotes the rapid compensation and diffusion of oxygen between flow channels. The overall liquid water saturation is relatively low. The high velocity vector around the outlet facilitates the drainage effect.

    Reviews on proton membrane materials for metal-organic frameworks in fuel cells
    ZHANG Jing, LIU Yuzhou, HE Beibei, ZHAO Ling
    2022, 44(8):  97-106.  doi:10.3969/j.issn.2097-0706.2022.08.011
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    A proton exchange membrane fuel cell(PEMFC) is a clean and efficient energy conversion device. Proton exchange membrane,as an important component of a PEMFC, can selectively permit the transfer of protons. However, high cost and poor stability against high temperature of proton exchange membranes restrict their practical applications in wide temperature range. Metal organic framework (MOF) materials are widely applied in catalytic and adsorption fields due to their facile synthesis, robust structures and high specific surface areas. In recent years, it has been revealed that a few MOF materials with high proton conductivity and low cost are deemed as potential alternatives for proton exchange membranes. Herein, the synthesis, chemical stability, proton conductivity and mechanism of MOF materials are discussed based on organic ligands (carboxylate, phosphonate, sulfonate, etc.) and guest molecules (imidazole, ammonium ion, etc.). The development prospect, future challenges and feasible strategies of the conductive MOF materials are also proposed.