High performance and stability of double perovskite-type oxide NdBa0.5Ca0.5Co1.5Fe0.5O5+δas an oxygen electrode for reversible solid oxide electrochemical cell

In this study,we successfully synthesized double perovskite-type oxide NdBa0.5Ca0.5Co1.5Fe0.5O5+δ(NBCCF)using a conventional wet chemical method as the oxygen electrode for reversible solid oxide electrochemical cells(RSOCs).The polarization resistance(Rp)of the composite electrode NBCCFGd0.1Ce0.9O2(GDC)is only 0.079Ωcm^2 at 800℃under air.The single cell based on NBCCF-GDC electrode displays a peak power density of 0.941 W/cm^2 in fuel cell mode and a low Rp value of 0.134Ωcm^2.In electrolysis cell mode,the cell displays an outstanding oxygen evolution reaction(OER)activity and shows current density as high as 0.92 A/cm^2 with 50 vol%AH(Absolute Humidity)at 800℃and applied voltage of 1.3 V.Most importantly,the cell exhibits admirable durability of 60 h both in electrolysis mode and fuel cell mode with distinguished reversibility.All these results suggest that NBCCF is a promising candidate electrode for RSOC.

Pd-La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ)composite as active and stable oxygen electrode for reversible solid oxide cells

To promote the electrocatalytic activity and stability of traditional(a_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ)(LSCF)oxygen electrodes in reversible solid oxide cells(RSOCs),conventional physical mixed method was used to prepare the Pd-LSCF composite oxygen electrode.The cell with Pd-LSCF|GDC|YSZ|Ni-YSZ configuration shows perfect electrochemical performance in both solid oxide fuel cell(SOFC)mode and solid oxide electrolysis cell(SOEC)mode.In the SOFC mode,the cell achieves a power density of 1.73 W/cm^(2)at800℃higher than that of the LSCF oxygen electrode with 1.38 W/cm^(2).In the SOEC mode,the current density at 1.5 V is 1.67 A/cm^(2)at 800℃under 50 vol%steam concentration.Moreover,the reversibility and stability of the RSOCs were tested during 192 h long-term reversible operation.The degradation rate of the cell is only 2.2%/100 h and 2.5%/100 h in the SOEC and the SOFC modes,respectively.These results confirm that compositing Pd with the LSCF oxygen electrode can considerably boost the electrochemical performance of LSCF electrode in RSOCs field.

K-doped BaCo_(0.4)Fe_(0.4)Zr_(0.2)O_(3−δ) as a promising cathode material for protonic ceramic fuel cells

Slow oxygen reduction reaction(ORR)involving proton transport remains the limiting factor for electrochemical performance of proton-conducting cathodes.To further reduce the operating temperature of protonic ceramic fuel cells(PCFCs),developing triple-conducting cathodes with excellent electrochemical performance is required.In this study,K-doped BaCo_(0.4)Fe_(0.4)Zr_(0.2)O_(3−δ)(BCFZ442)series were developed and used as the cathodes of the PCFCs,and their crystal structure,conductivity,hydration capability,and electrochemical performance were characterized in detail.Among them,Ba_(0.9)K_(0.1)Co_(0.4)Fe_(0.4)Zr_(0.2)O_(3−δ)(K10)cathode has the best electrochemical performance,which can be attributed to its high electron(e^(−))/oxygen ion(O^(2−))/H^(+)conductivity and proton uptake capacity.At 750℃,the polarization resistance of the K10 cathode is only 0.009Ω·cm^(2),the peak power density(PPD)of the single cell with the K10 cathode is close to 1 W·cm^(−2),and there is no significant degradation within 150 h.Excellent electrochemical performance and durability make K10 a promising cathode material for the PCFCs.This work can provide a guidance for further improving the proton transport capability of the triple-conducting oxides,which is of great significance for developing the PCFC cathodes with excellent electrochemical performance.

Materials of solid oxide electrolysis cells for H_(2)O and CO_(2) electrolysis:A review

Reliable and economical energy storage technologies are urgently required to ensure sustainable energy supply.Hydrogen(H_(2))is an energy carrier that can be produced environmentfriendly by renewable power to split water(H_(2)O)via electrochemical cells.By this way,electric energy is stored as chemical energy of H_(2),and the storage can be large-scale and economical.Among the electrochemical technologies for H_(2)O electrolysis,solid oxide electrolysis cells(SOECs)operated at temperatures above 500℃have the benefits of high energy conversion efficiency and economic feasibility.In addition to the H_(2)O electrolysis,SOECs can also be employed for CO_(2) electrolysis and H2O–CO_(2) co-electrolysis to produce value-added chemicals of great economic and environmental significance.However,the SOEC technology is not yet fully ready for commercial deployment because of material limitations of the key components,such as electrolytes,air electrodes,and fuel electrodes.As is well known,the reactions in SOEC are,in principle,inverse to the reactions in solid oxide fuel cells(SOFCs).Component materials of SOECs are currently adopted from SOFC materials.However,their performance stability issues are evident,and need to be overcome by materials development in line with the unique requirements of the SOEC materials.Key topics discussed in this review include SOEC critical materials and their optimization,material degradation and its safeguards,future research directions,and commercialization challenges,from both traditional oxygen ion(O_(2)−)-conducting SOEC(O-SOEC)and proton(H^(+))-conducting SOEC(H-SOEC)perspectives.It is worth to believe that H_(2)O or/and CO_(2) electrolysis by SOECs provides a viable solution for future energy storage and conversion.

Recent progress of g-C_(3)N_(4) applied in solar cells

Graphite carbon nitride(gC_(3)N_(4)),a two-dimensional polymer semiconductor material,has good semiconductor properties,suitable electronic energy band structure,excellent physical and chemical stability.It is widely used in the field of energy and materials science such as photoelectric conversion.In this paper,the progress of g-C_(3)N_(4) in dye sensitized solar cells(DSSC)and perovskite solar cells(PSC)was reviewed.As a new semiconductor material,g-C_(3)N_(4) has the advantages of simple preparation,abundant amino and Lewis basic groups.Therefore,on the basis of excellent structure of g-C_(3)N_(4),its electronic and optical properties are utilized to further expand its application in the field of photoelectric conversion.

制备无锶无钴的钙钛矿氧化物作为高性能可逆固体氧化物电池的空气电极(英文)

可逆固体氧化物燃料电池(RSOC)是一种新型高效的能量存储和转化装置,具有高效率、无污染和模块化等优点.在本文中,La_(0.6)Ca_(0.4)Fe_(0.8)Ni_(0.2)O_(3-δ)(LCaFN)被用于高性能RSOC的无锶无钴钙钛矿空气电极.与La_(0.6)Ca_(0.4)Fe_(0.8)Ni_(0.2)O_(3-δ)(LSFN)和La_(0.6)Ca_(0.4)Fe_(0.8)Ni_(0.2)O_(3-δ)(LSCoF)相比,LCaFN具有较高的导电性(297 S cm^(-1))、良好的热膨胀系数兼容性(11.2×10^(-6)K^(-1))和较高的化学稳定性.此外,LCaFN在800℃还具有高催化活性和低极化电阻(0.06Ωcm^(2)).单电池Ni-YSZ/YSZ/GDC/LCaFN-GDC在800℃下的最大功率密度为1.08 W cm^(-2).在固体氧化物电解池模式下,电池在800℃、70%H_(2)O、1.3 V电压下可实现约1.2 A cm^(-2)的电流密度.同时电池还表现出良好的可逆性和运行稳定性.研究结果表明,LCaFN作为RSOC的空气电极材料具有广阔的应用前景.

Microstructure, hardness and contact fatigue properties of X30N high nitrogen stainless bearing steel

Microstructure, hardness and fatigue properties of X30N high nitrogen stainless bearing steel were investigated. It was found that nitrogen addition could effectively reduce the amount and size of coarse carbides. The original austenite grain size was obviously refined. Additionally, more retained austenite was found in X30N steel after quenching at 1050 ℃, which could be reduced from about 30% to about 6% by cold treatment at - 73 ℃ and subsequent tempering, and thus, the ultimate hardness was increased up to about 61 HRC with reduction of austenite and precipitation of carbonitrides. Furthermore, the rolling contact fatigue lives of X30N steel ate superior to those of 440C steel, which was attributed to the enhanced hardness and a certain retained austenite in the high nitrogen steel.

Comparison of microstructure and property of high chromium bearing steel with and without nitrogen addition

Microstructure and property of bearing steel with and without nitrogen addition were investigated by microstructural observation and hardness measurement after different heat treatment processing. Based on the microstructural observation of both 9Cr18 steel and X90N steel, it was found that nitrogen addition could effectively reduce the amount and size of coarse carbides and also refine the original austenite grain size. Due to addition of nitrogen, more austenite phase was found in X90N steel than in 9Cr18 steel. The retained austenite of X90N steel after quenching at 1050℃ could be reduced from about 60% to about 7 9% by cold treatment at -73℃ and subsequent tempering, and thus finally increased the hardness up to 60 HRC after low temperature tempering and to 63 HRC after high temperature tempering. Furthermore, both the wear and corrosion resistance of X90N steel were found much more superior than those of 9Cr18 steel, which was attributed to the addition of nitrogen. It was proposed at last that nitrogen alloying into the high chromium bearing steel was a promising way not only to refine the size of both carbides and austenite, but also to achieve high hardness, high wear property and improved corrosion resistance of the stainless bearing steel.