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.

Modelling of thrust generated by oscillation caudal fin of underwater bionic robot

A simplified model of the thrust force is proposed based on a caudal fin oscillation of an underwater bionic robot. The caudal fin oscillation is generalized by cen- tral pattern generators （CPGs）. In this model, the drag coefficient and lift coefficient are the two critical parameters which are obtained by the digital particle image velocimetry （DPIV） and the force transducer experiment. Numerical simulation and physical experi- ments have been performed to verify this dynamic model.

Improved water oxidation via Fe doping of CuWO4 photoanodes:Influence of the Fe source and concentration

Iron(Fe)was successfully doped in CuWO4 photoanode films with a combined liquid-phase spin-coating method via the dopant sources of Fe(NO3)3,FeSO4 and FeCl3.The microstructure of the prepared films was characterized by x-ray diffraction,scanning electron microscopy,and atomic force microscopy.The light absorption and photoelectric conversion properties were evaluated by the UV-visible absorption spectra and monochromatic incident photon-to-electron conversion efficiency.The chemical composition and element combination of the samples were examined by x-ray photoelectron spectroscopy.A linear sweep voltammetric and stability test(I-t)were performed with an electrochemical workstation.The results show that the samples are uniform with a thickness of approximately 800 nm and that the photoelectrochemical performance of the doped films is heavily dependent on the Fe source and dopant concentration.Upon optimizing the doping conditions of Fe(NO3)3 and the optimal source,the photocurrent density in the Fe-doped CuWO4 photoanode film is improved by 78%from 0.267 mA/cm2 to 0.476 mA/cm2 at 1.23 V vs reversible hydrogen electrode.The underlying causes are discussed.

Advances in component and operation optimization of solid oxide electrolysis cell

Considering the earth powered by intermittent renewable energy in the coming future,solid oxide electrolysis cell(SOEC)will play an indispensable role in efficient energy conversion and storage on demand.The thermolytic and kinetic merits grant SOEC a bright potential to be directly integrated with electrical grid and downstream chemical synthesis process.Meanwhile,the scientific community are still endeavoring to pursue the SOEC assembled with better materials and operated at a more energy-efficient way.In this review article,at cell level,we focus on the recent development of electrolyte,cathode,anode and buffer layer materials for both steam and CO_(2)electrolysis.On the other hand,we also discuss the next generation SOEC operated with the assistant of other fuels to further reduce the energy consumption and enhance the productivity of the electrolyzer.And stack level,the sealant,interconnect and stack operation strategies are collectively covered.Finally,the challenges and future research direction in SOECs are included.

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.

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.

Boosting carrier dynamics of BiVO_(4) photoanode via heterostructuring with ultrathin BiOI nanosheets for enhanced solar water splitting

Bismuth vanadate(BiVO_(4))has been one of the most promising candidates for solar water splitting while still suffers from poor bulk charge transport that limits its solar to hydrogen conversion efficiency.We demonstrate in this work an efficient strategy for boosting bulk charge transport of BiVO_(4) through the facile impregnation of as-prepared BiVO_(4) photoanode in the precursor solution of ultrathin BiOI nanosheets.Such impregnation creates increased oxygen vacancies in the bulk of BiVO_(4) through the reduction of V^(5+)to V^(4+)by I^(-),which greatly improves bulk separation efficiency for BiVO_(4)-BiOI up to 65.9%at 1.23 V_(RHE) from the original 51.9%of pure BiVO_(4).Moreover,the decoration of the BiOI nanosheets on BiVO_(4) photoanode is also beneficial for addressing the carrier dynamics at surface due to the matched energy levels of BiOI nanosheets and BiVO_(4).The introduced plenty of oxygen vacancies in the bulk of BiVO_(4) and the built-in electric field in BiVO_(4)-BiOI synergistically improve the photocurrent density at 1.23 V_(RHE) up to 3.88 mA cm^(-2).We believe that such facile impregnation strategy will pave an alternative way to the development of highly efficient BiVO_(4) photoanode.

Sputtering Deposition of Ultra-thin α-Fe_2O_3 Films for Solar Water Splitting

Ultra-thin α-Fe2O3（hematite） films have been deposited by radio frequency（RF） sputtering technique and photoelectrochemically investigated towards their ability to oxidize water.By varying the deposition power and time as well as the sputter gas flow（argon）,the microstructure and morphology of the film were optimized.It was found that the increment in the film thickness resulted in the loss of efficiency for solar water oxidation.The film with a thickness of 27 nm exhibited the best result with a maximum photocurrent of 0.25 mA cm-2at 1.23 VRHE.Addition of small amounts of O2to the sputter gas improved the photoactivity significantly.

A new popular transition metal-based catalyst:SmMn_(2)O_(5) mullite-type oxide

Catalyst with high performance has drawn increasing attention recently due to its significant advantages in chemical reactions such as speeding up the reaction,lowering the reaction temperature or pressure,and proceeding without itself being consumed.Despite the superior catalytic performance of precious metal catalysts,transition metal oxides offer a promising route for substitution of precious metals in catalysis arising from their low cost,intrinsic activity and sufficient stability.Mullite-type oxide SmMn_(2)O_(5) exhibits a unique crystal structure containing double crystalline fields,and nowadays is used widely as the catalyst in different chemical reactions,including the reactions of vehicle emissions reduction and oxygen evolution reaction,gas sensors,and metal-air batteries,promoting attention in catalytic perfor-mance enhancement.To our knowledge,there is no review article covering the comprehensive informa-tion of SmMn2 O 5 and its applications.Here we review the recent progress in understanding of the crys-tal structure of SmMn_(2)O_(5) and its basic physical properties.We then summarize the catalytic sources of SmMn_(2)O_(5) and reaction mechanisms,while the strategies to improve catalytic performance of SmMn_(2)O_(5) are further presented.Finally,we provide a perspective on how to make further progress in catalytic applications.

BaCe_(0.8)Fe_(0.1)Ni_(0.1)O_(3−δ)-impregnated Ni-GDC by phase-inversion as an anode of solid oxide fuel cells with on-cell dry methane reforming

BaCe_(0.8)Fe_(0.1)Ni_(0.1)O_(3−δ)(BCFN)in a perovskite structure is impregnated consecutively by BCFN solution and BCFN suspension into a phase-inversion prepared NiO–Gd_(0.1)Ce_(0.9)O_(2−δ)(GDC)scaffold as an anode for solid oxide fuel cells(SOFCs)with on-cell dry reforming of methane(DRM).The whole pore surface of the scaffold is covered by small BCFN particles formed by BCFN solution impregnation;the large pores near the scaffold surface are filled by BCFN aerogels with a high specific surface area produced by BCFN suspension impregnation,which act as a catalytic layer for on-cell DRM.After reduction,the anode consists of a Ni–GDC scaffold and BCFN particles with exsolved FeNi3 nanoparticles.This BCFN-impregnated Ni–GDC anode has higher electrical conductivity,electrochemical activity,and resistance to carbon deposition,with which the cell shows maximum power densities between 1.44 and 0.92 W·cm^(−2) when using H_(2) and between 1.09 and 0.50 W·cm^(−2) when using CO_(2)–CH_(4) at temperatures ranging from 750 to 600℃.A stable performance at 400 mA·cm^(−2) and 700℃is achieved using 45%CO_(2)–45%CH_(4)–10%N_(2) for more than 400 h without carbon deposition,benefiting from the impregnated BCFN aerogel with a high specific surface area and water adsorbability.