Browsing by Author "Zhao, Yicheng"

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  • A 98.2% energy efficiency Li-O2 battery using a LaNi-0.5Co0.5O3 perovskite cathode with extremely fast oxygen reduction and evolution kinetics
    (2023-01-15) Qiu, Qianyuan; Pan, Zheng-Ze; Yao, Penghui; Yuan, Jiashu; Xia, Chun; Zhao, Yicheng; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Rechargeable lithium-oxygen (Li-O2) batteries have been regarded as a promising energy storage device, but its practical use is impeded by its low energy efficiency. Herein, a bi-functional catalytic perovskite LaNi0.5Co0.5O3 (LNCO) is employed as the cathode of an efficient Li-O2 battery with a molten nitrate salt electrolyte at 160 °C. It displays a stable low charge–discharge overpotential 50 mV with a high energy efficiency (EE) 98.2 % at 0.1 mA cm−2 for over 100 cycles. The excellent performance is attributed to the extremely fast oxygen reduction and evolution kinetics on the surface of LNCO. The discharge product is Li2O with a porous and fluffy morphology which facilitates the transfer of oxygen and other intermediate species. It is noted that Li2O as a discharge product enables a theoretical specific energy density of 5200 Wh kg−1, which is superior to the Li2O2 as product giving 3500 Wh kg−1 for those ambient temperature Li-O2 batteries.
  • A-site ordered double perovskite with in situ exsolved core-shell nanoparticles as anode for solid oxide fuel cells
    (2019-02-20) Hou, Nianjun; Yao, Tongtong; Li, Ping; Yao, Xueli; Gan, Tian; Fan, Lijun; Wang, Jun; Zhi, Xiaojing; Zhao, Yicheng; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A highly active anode material for solid oxide fuel cells resistant to carbon deposition is developed. Co-Fe co-doped La 0.5 Ba 0.5 MnO 3- with a cubic-hexagonal heterogeneous stucture is synthesized through the Pechini method. An A-site ordered double perovskite with Co 0.94 Fe 0.06 alloy-oxide core-shell nanoparticles on its surface is formed after reduction. The phase transition and the exsolution of the nanoparticles are investigated with X-ray diffraction, thermogravimetric analysis, and high-resolution transmission electron microscope. The exsolved nanoparticles with the layered double-perovskite supporter show a high catalytic activity. A single cell with that anode and a 300 μm thick La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3 electrolyte layer exhibits maximum power densities of 1479 and 503 mW cm -2 at 850 °C with wet hydrogen and wet methane fuels, respectively. Moreover, the single cell fed with wet methane exhibits a stable power output at 850 °C for 200 h, demonstrating a high resistance to carbon deposition of the anode due to the strong anchor of the exsolved nanoparticles on the perovskite parent. The oxide shell also preserves the metal particles from coking.
  • Achieve a high electrochemical oxidation activity by a self-assembled cermet composite anode with low Ni content for solid oxide fuel cells
    (2023-10) Wu, Bingxue; Zhang, Jian; Yang, Zhi; Lu, Xuanlin; Zhao, Xin; Liu, Wen; Chen, Jiaxuan; Zhao, Yicheng; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Ni-based cermets are the most widely used anode materials for solid oxide fuel cells. Reducing the content of Ni is beneficial to anode stability but usually unfavorable for the catalytic activity. In this study, Ni-Ce0.8Sm0.2O2-δ anode with a low Ni content is synthesized through a polymer-directed evaporation-induced self-assembly strategy. Ni distributes evenly in the anode, resulting in an enlarged triple-phase boundary region and improved reactivity of lattice oxygen in the oxide phase. The anode containing 5 wt.% Ni possesses the highest amounts of oxygen vacancies and Ce3+/Ce4+ redox pairs that facilitates the charge transfer process, which is one of the rate-determining steps of anode reaction. Consequently, that anode shows the lowest polarization resistance of 0.014 Ω cm2 at 700 °C, much lower than those of other Ni-based anodes prepared through conventional techniques such as impregnation and solid-mixing. With that anode, a single cell supported by a 480-μm-thick Ce0.8Sm0.2O2-δ electrolyte layer exhibits the maximum power density of 270 mW cm−2 at 700 °C. The anode also shows a promising stability.
  • Black TiO2-supported copper nanoparticles for efficient photocatalytic N-formylation of N-methylaniline with CO2
    (2023-05) Yuan, Shibo; Bai, Peng; He, Yi; Chen, Jiafa; Zhao, Yicheng; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Photocatalytic N-formylation of amines with CO2 is a promising strategy to convert CO2 into value-added chemicals sustainably. In this work, a black TiO2-supported Cu photocatalyst is prepared through a solvothermal method for the N-formylation of N-methylaniline with NaBH4 as the reducing agent. Cu nanoparticles and oxygen vacancies are formed on the surface of the photocatalyst after reduction with H2, which decreases the band-gap energy and promotes the separation of photogenerated electrons and holes, thereby improving the photocatalytic activity remarkably. A 100 % conversion is achieved after 9 h radiation, and the yield of N-methylformanilide reaches 81 %. Both the amount of NaBH4 and the pressure of CO2 show important influences on the activity and selectivity of the photocatalytic process, and the carbon and hydrogen in the aldehyde group are from CO2 and NaBH4, respectively. The photocatalyst also shows promising cycling durability.
  • Bulk phase charge transfer in focus – And in sequential along with surface steps
    (2021-03-15) Pan, Zhengze; Li, Yongdan; Zhao, Yicheng; Zhang, Cuijuan; Chen, Hong
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    In recent decades, catalysis has witnessed increasing interests in many catalytic reactions with bulk phase and interface charge transfer steps as a distinguished feature. Here, the charge can be cations, anions, electrons or holes. Research into both bulk phase and interface charge transfer has changed our understanding and in-focus design of catalysts and reactors, due to the clear difference in kinetics from those classical catalytic reactions, where only surface steps are concerned. This perspective selects several types of representative reactions and discusses the challenges and opportunities to innovations in catalytic technologies from the viewpoint of recognizing and accelerating the key step of the charge transfer at interface or in the catalyst bulk phase, as well as incorporating the surface steps into the overall kinetics.
  • Cathode electrocatalyst in aprotic lithium oxygen (Li-O2) battery: A literature survey
    (2023-08-01) Qiu, Qianyuan; Long, Jilan; Yao, Penghui; Wang, Jiaqi; Li, Xiang; Pan, Zheng-Ze; Zhao, Yicheng; Li, Yongdan
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    Lithium oxygen battery (LOB) is a highly promising energy storage device for the next generation electric vehicles due to its high theoretical energy density. However, many challenges hinder its practical application. The electrochemical performances, such as discharge capacity, discharge and charge overpotentials, power density and stability are all far from satisfactory. In recent years, a great progress has been made and numerous works on cathode materials have been published. This article focuses on the state-of-the-art of LOB cathode materials and the reaction mechanism happens on the cathode. The principles of cathode reactions are summarized and the requirements for cathode materials are discussed. The performance of LOBs with carbon-based and carbon free cathode materials are described. The approaches on improving the cathode performance via temperature increase, material surface engineering, texture optimization and oxygen vacancy regulation are elaborated. A perspective on the research trend on the cathode catalyst is finally proposed.
  • A cobalt-free Pr6O11–BaCe0.2Fe0.8O3-δ composite cathode for protonic ceramic fuel cells with promising oxygen reduction activity and hydration ability
    (2024-04-15) Lu, Xuanlin; Yang, Zhi; Zhang, Jian; Zhao, Xin; Chen, Jiaxuan; Liu, Wen; Zhao, Yicheng; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Oxygen reduction and proton conduction originated from hydration are two key steps in the cathode process of protonic ceramic fuel cells. In this work, Pr6O11 is impregnated into a cobalt-free BaCe0.2Fe0.8O3-δ cathode, resulting in an improved activity of lattice oxygen and a moderate enhancement of the electrical conductivity, both of which are beneficial for charge transfer, the rate-determining step of oxygen reduction process at the cathode. The polarization resistance of bare BaCe0.2Fe0.8O3-δ cathode for oxygen reduction is 0.115 Ω cm2 at 700 °C, which is reduced significantly to 0.039 Ω cm2 with the addition of 30 wt% Pr6O11. Besides, the hydration ability of the cathode is also improved with Pr6O11, and thus the combination of proton and oxygen is facilitated. A single cell with 30 wt% Pr6O11-70 wt% BaCe0.2Fe0.8O3-δ composite cathode exhibits the highest maximum power density of 1406 mW cm−2 at 700 °C. The composite cathode also shows a good stability.
  • Coking resistant Ni–La0.8Sr0.2FeO3 composite anode improves the stability of syngas-fueled SOFC
    (2021-02-26) Yao, Xueli; Asghar, Muhammad Imran; Zhao, Yicheng; Li, Yongdan; Lund, Peter D.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    An improved SOFC anode with excellent stability against carbon deposition with syngas as fuel is reported. The anode material is Ni–La0.8Sr0.2FeO3 (LSF) composite synthesized by anhydrous impregnation. After reduction in wet H2 (3% H2O), the material partially decomposes to SrLaFeO4 and exsolved Fe. The exsolved Fe forms Ni–Fe alloy with impregnated Ni. The particle size of Ni–Fe alloy is about 20–50 nm. The Ni–Fe alloy nanoparticles disperse on the surface of the La0.8Sr0.2FeO3 and SrLaFeO4 oxides. The increase of Ni content promotes the exsolution of Fe and increases the reaction sites of Ni–Fe alloy. With the increase of the Ni content, the electrical conductivity and catalytic activity are enhanced, which improves the electrochemical performance of the single cell. The cell with 10 mol.% Ni impregnated Ni-LSF as anode achieves a maximum power density of 550 mW cm−2 at 700 °C fueled with syngas. The strong interaction of the nano-sized Ni–Fe alloy with the LaxSryFeOz (La0.8Sr0.2FeO3 or SrLaFeO4) oxide substrate efficiently suppresses carbon deposition with high graphitization degree. Besides, the SrLaFeO4 phase which can accommodate interstitial oxygen facilitates the removal of the deposited carbon.
  • Cu-Ce0.8Sm0.2O2-δ anode for electrochemical oxidation of methanol in solid oxide fuel cell: Improved activity by La and Nd doping
    (2021-10-15) Zhang, Yongxin; Huang, Zhiyong; Gan, Tian; Hou, Nianjun; Fan, Lijun; Zhou, Xin; Gao, Ge; Li, Jingyu; Zhao, Yicheng; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Cu–Ce0.8La0.1Sm0.1O2-δ and Cu–Ce0.8Nd0.1Sm0.1O2-δ are studied as anode materials for solid oxide fuel cells with methanol as fuel. The oxygen surface exchange and bulk diffusion coefficients of Ce0.8Sm0.2O2-δ both increase with La and Nd doping. The CH3OH temperature-programmed surface reaction results show that the addition of La and Nd accelerates the chemical oxidation of CH3OH. Furthermore, compared with Cu–Ce0.8Sm0.2O2-δ, the anodes with La and Nd show higher resistance to coking in CH3OH atmosphere. The Cu-based cermet anode exhibits a low catalytic activity for the electrochemical oxidation of H2, and a single cell supported by a Ce0.8Sm0.2O2-δ‑carbonate composite electrolyte with Cu–Ce0.8Sm0.2O2-δ anode exhibits a maximum power density of 160 mW cm−2 at 650 °C using dry hydrogen as fuel. However, the maximum power density reaches 550 mW cm−2 when CH3OH is used as fuel, and further increases to 730 and 830 mW cm−2 with the addition of La and Nd in the anode, respectively. The results indicate that with the promotion of the oxygen activity, the Cu-based cermet is a promising anode material for solid oxide fuel cells using CH3OH as fuel.
  • Design of a perovskite oxide cathode for a protonic ceramic fuel cell
    (2024-01-01) Yao, Penghui; Zhang, Jian; Qiu, Qianyuan; Li, Gen; Zhao, Yicheng; Yu, Fangyong; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    High catalytic activity, low-cost and stable cathode in a temperature range 550–700 °C is essential for the development of protonic ceramic fuel cells (PCFCs). Doping nickel into perovskite La0.5Sr0.5MnO3-δ(LSM) is designed as a cobalt-free cathode based on theoretical calculations and experiments. La0.5Sr0.5Mn0.9Ni0.1O3-δ (LSMNi) as cathode shows higher proton conductivity and ORR activity than the undoped LSM. The PCFCs with LSMNi exhibit low polarization resistance and high peak power density 1.1 W cm−2 at 700 °C. The density functional theory simulations indicate that doping with nickel decreases the oxygen vacancy formation energy and promotes the formation of hydroxide defects. The decrease in proton transfer energy barriers and hydration energy improves the proton conductivity. The improved performance is attributed to fast proton transfer and rapid kinetics of oxygen reduction on the surface of LSMNi. This work provides a novel approach to design cobalt-free cathode for a protonic ceramic fuel cell.
  • A dual modification strategy of highly active catalytic cathode for proton-conducting solid oxide fuel cell with Ni-doped PrBaFe1.9Mo0.1O6-δ
    (2024-06-30) Yao, Penghui; Zhang, Jian; Qiu, Qianyuan; Zhao, Yicheng; Yu, Fangyong; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The cathode catalytic activity and stability in a temperature range of 550–700 °C is crucial to the development of proton-conductive solid oxide fuel cells (PCFCs). A facile dual-modification strategy is developed for the design of Ni-doped PrBaFe1.9Mo0.1O6-δ (PBFMN), composed of a major perovskite and a minor NiO phases, as a cobalt-free cathode. The composite cathode PBFMN exhibits high catalytic activity and stability. Computational simulation indicates that the perovskite phase increases the oxygen vacancies and enhances the proton transfer, while nickel oxide nanoparticles improve oxygen adsorption and dissociation. The fuel cell with as-prepared PBFMN reached a peak power density 1.23 W cm−2 at 700 °C. The improved performance of the cell is mainly due to the fast ORR kinetics. This work provides a new insight into the design of cobalt-free cathode for a PCFC.
  • Effect of Sn addition on improving the stability of Ni-Ce0.8Sm0.2O1.9 anode material for solid oxide fuel cells fed with dry CH4
    (2019-06-15) Li, Ping; Wang, Zhiming; Yao, Xueli; Hou, Nianjun; Fan, Lijun; Gan, Tian; Zhao, Yicheng; Li, Yongdan; Schwank, Johannes W.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Sn-NiO-Ce0.8Sm0.2O1.9 (SDC) is synthesized as an anode material for solid oxide fuel cells with H2 and dry methane as fuels. Sn-Ni alloy is formed after reduction. The performances of anode-supported single cells with a configuration of Sn-Ni-SDC|SDC|Ba0.5Sr0.5Co0.8Fe0.2O3-δ are investigated in the range of 600–700 °C. With increasing Sn content of the anode, the performances of the cells fed with H2 and dry methane both decrease slightly, indicating a reduced anodic catalytic activity. However, the stability of the cell with dry methane as fuel improves remarkably with the addition of Sn due to the suppression of carbon deposition on the anode.
  • Effects of manganese oxides on the activity and stability of Ni-Ce0.8Sm0.2O1.9 anode for solid oxide fuel cells with methanol as the fuel
    (2019-06-15) Gan, Tian; Ding, Guochang; Chen, Boran; Zhi, Xiaojing; Li, Ping; Yao, Xueli; Hou, Nianjun; Fan, Lijun; Zhao, Yicheng; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Ni-MnOx-Ce0.8Sm0.2O1.9 (SDC) composites are synthesized and investigated as anode materials of solid oxide fuel cells fed with methanol. The lowest anodic polarization resistance is obtained when the molar ratio of Mn to Ni is 0.05:0.95. The high catalytic activity is attributed to the transfer of electrons from Ni to Mn and the increase of the content of the lattice oxygen in the anode. The single cell with that anode and SDC-carbonate composite electrolyte exhibits a maximum power density of 722 mW cm-2 at 700 °C. Mn also increases the resistance to carbon deposition of the anode due to the high lattice oxygen content and the redox cycle of the Mn species. The stability of the single cell is enhanced with the increase of the content of Mn in the anode.
  • The effects of potential and solar input on Z-scheme C3N4-TiO2 nanotubes @ Ti electrode in a broad potential window
    (2023-05-01) Hou, Xuelan; Zhao, Yicheng; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Construction of Z-scheme graphitic carbon nitride-titanium dioxide nanotubes (C3N4-TNT) has been known useful to optimize the band structure for improving photon capture and for accelerating charge carrier separation and transfer rate in photoelectrochemical water splitting (PECWS) cells. However, the reported operating potential window in a PECWS cell, often in 0 – 1.23 VRHE (volt versus reversible hydrogen electrode) plus its overpotential, is too narrow to understand the C3N4-TNT electrode. Herein, a broad potential window of −0.5 − 2.5 VRHE is applied to C3N4-TNT@Ti and recorded via the polarization test under chopped sunlight to analyze the effect of both electrons from external electrical circuit and photons from simulated sunlight. In 0 – 2.5 VRHE, the potential enhances the photocurrent density. For example, at 1.6 VRHE, the C3N4-TNT sample exhibits 1.8-time higher photocurrent density than that of pure TNT. In −0.5 − 0 VRHE, i.e., both samples do not give photo-current response. In addition, for advanced water oxidation/reduction beyond WS to oxygen/hydrogen, a large potential window will be expected. Further, the light capture ability, the charge carrier recombination rate, and the electron flow path through the C3N4-TNT junction without and with reverse/forward potentials are discussed to elucidate the effect of the applied potential.
  • An Efficient and Stable Lithium-Oxygen Battery Based on Metal-Organic Framework Separator Operating at 160 °C
    (2023-12-21) Qiu, Qianyuan; Yuan, Jiashu; Li, Gen; Pan, Zheng-ze; Yao, Penghui; Zhao, Yicheng; Zhang, Cuijuan; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A lithium oxygen battery (LOB) with molten salt electrolyte operating at elevated temperature has aroused great interest because it enables fast reaction kinetics. However, there is still a lack of open literature on the separator (membrane) of this kind of LOB. Metal-organic framework (MOF) materials are widely used as components of separators in many kinds of energy storage devices, due to their regular crystalline and well-defined pore structures. In this work, a MOF material, zirconium (II) 1,4-benzenedicarboxylate after lithiation (UiO-66-SO3Li) with a narrow pore size (6 Å), is used as a key component of the separator for LOB operating at elevated temperature. A “rolling dough” method is adopted to prepare the separator, which achieves 100% material utilization. The LOB with this membrane operates at 160 °C and delivers a specific capacity of 5.1 mAh cm−2 with an overpotential as low as 40 mV at 0.1 mA cm−2 and a prolonged cycle life, 180 cycles with a high coulombic efficiency of 99.9% at 0.5 mA cm−2. This MOF-based membrane provides efficient Li+ transfer and restricts discharge product migration during battery operation, which is promising for the development of LOB in large-scale practical applications.
  • Efficient photocatalytic CO2 N-formylation of amines over Pd/Bi-ZnOx without extra reductant
    (2024-03-15) Bai, Peng; Zhao, Yicheng; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Photocatalytic N-formylation of amines with CO2 is a promising strategy to convert CO2 into value-added chemicals sustainably. In this work, Pd-Bi bimetallic modified ZnO enriched in oxygen vacancies is constructed for photocatalytic CO2 formylation of benzylamine at room temperature without any reductants. The Pd and Bi sites reduce the band gap energy of ZnO, promote the separation of the photogenerated charge carriers and enhance the adsorption capacity of CO2. The yield of N-benzylformamide reaches 31.7 mmol g−1 with a selectivity of 85.3 % after 3-hour radiation in N,N-dimethylformamide (DMF) solvent. The aldehyde group involved in the formylation of benzylamine is derived from the decomposition of DMF, which is regenerated with the aldehyde group coming from the reduction of CO2. The decomposition-regeneration cycle of DMF solvent enlarges the reaction region, which is beneficial to the activity and selectivity of the formylation process. The synergistic photocatalytic system shows a good universality. This study provides a new approach to high-efficiency CO2 utilization and formamide production.
  • Efficient photocatalytic CO2 reduction coupled with selective styrene oxidation over a modified g-C3N4/BiOBr composite with high atom economy
    (2024-02-21) Bai, Peng; Zhao, Yicheng; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Conventional photocatalytic CO2 reduction is usually combined with the oxidation of H2O or sacrificial agents, which faces problems such as low catalytic activity and inefficient atom economy. In this work, a photocatalytic CO2 reduction and selective styrene oxidation synergetic system is developed with an NH4Cl-modified g-C3N4/BiOBr composite photocatalyst. The interfacial heterostructure promotes the formation of surface amino groups and oxygen vacancies, which facilitates the adsorption and chemical reduction of CO2. The heterostructure also improves the separation of photogenerated electron-hole pairs and enhances the photocatalytic activity. The simultaneous consumption of electrons and holes is beneficial for both CO2 reduction and styrene oxidation processes. Meanwhile, the oxygen atoms removed during CO2 reduction are utilized efficiently for styrene oxidation in this synergistic system, and thus the atom economy is improved significantly. The generation rates of CO, CH4, benzaldehyde and styrene oxide are 802, 8, 684 and 139 μmol g−1 h−1, respectively. This study provides a novel strategy for designing a green photocatalytic CO2 reduction system.
  • Enhanced activity and stability of Sr 2 FeMo 0.65 Ni 0.35 O 6-δ anode for solid oxide fuel cells with Na doping
    (2019-06-15) Yao, Tongtong; Hou, Nianjun; Gan, Juanjuan; Wang, Jun; Zhi, Xiaojing; Fan, Lijun; Gan, Tian; Zhao, Yicheng; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Sr 2-x Na x FeMo 0.65 Ni 0.35 O 6-δ is synthesized as an anode material for solid oxide fuel cells. The effects of Na on the crystalline phase and electrical properties are investigated. The main perovskite phase changes into a Ruddlesden-Popper structure after reduction when x is less than 0.1, while the material with a higher amount of Na keeps the perovskite structure. FeNi x alloy nanoparticles are exsolved during reduction, in which the content of Ni increases with the rise of Na amount. The surface oxygen vacancy concentration is also influenced by the doping of Na, and the highest value is reached when x is 0.1. Sr 1.9 Na 0.1 FeMo 0.65 Ni 0.35 O 6-δ anode exhibits the highest activity, and a single cell supported by a 300-μm-thick La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3-δ electrolyte layer shows maximum power densities of 1495 and 627 mW cm −2 at 850 °C with H 2 and wet CH 4 as fuels, respectively. The coking resistance of the anode is also improved with Na doping.
  • Enhanced oxygen reduction reaction activity of BaCe0.2Fe0.8O3-δ cathode for proton-conducting solid oxide fuel cells via Pr-doping
    (2021-05-31) Zhou, Xin; Hou, Nianjun; Gan, Tian; Fan, Lijun; Zhang, Yongxin; Li, Jingyu; Gao, Ge; Zhao, Yicheng; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    BaCe0.2Fe0.8-xPrxO3-δ (x = 0–0.3) is studied as a cobalt-free cathode material for proton-conducting solid oxide fuel cells. The cathode is composed of a cubic BaFeO3-δ phase and an orthorhombic BaCeO3-δ phase, and Pr is doped in both phases. The partial substitution of Pr for Fe decreases the content of the BaFeO3-δ phase, leading to a lower electrical conductivity. BaCe0.2Fe0.6Pr0.2O3-δ has the most adsorbed oxygen and Fe3+ on the surface, resulting in the fastest oxygen surface exchange kinetics and the highest activity. The partial pressure of H2O shows a negligible effect on the polarization resistance of the cathode. In contrast, the polarization resistance increases remarkably with the decrease of oxygen partial pressure, indicating that the rate of the cathode process is controlled by the surface exchange of oxygen. At 700 °C, BaCe0.2Fe0.6Pr0.2O3-δ shows the lowest polarization resistance of 0.057 Ω cm2, and a single cell with that cathode exhibits the highest maximum power density of 562 mW cm−2. The results demonstrate that Pr doped BaCe0.2Fe0.8O3-δ is a promising cobalt-free cathode material for proton-conducting solid oxide fuel cells.
  • Enhancement of the electrocatalytic activity of La0.6Sr0.4Co0.2Fe0.8O3-δ through surface modification by acid etching
    (2021-03-15) Fan, Lijun; Wang, Jun; Huang, Zhiyong; Yao, Xueli; Hou, Nianjun; Gan, Tian; Gan, Juanjuan; Zhao, Yicheng; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The surface properties of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) perovskite electrode are modified with HNO3 treatment to improve its catalytic activity towards oxygen reduction reaction between 500–650 °C. The surface concentrations of A-site cations are reduced after the acid etching. After the calcination at 1150 °C, severe segregation of Sr is observed on the surface of untreated LSCF powder, which is suppressed remarkably with the HNO3 pretreatment. Highly reactive oxygen species and Fe4+ species are formed on the surface of LSCF after the HNO3 treatment, which are beneficial to oxygen reduction reaction. The reduction of oxygen species adsorbed on the LSCF surface, the rate-determining step of the electrode process, is accelerated significantly with the acid etching.