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We applied a novel solid-liquid co-electrospinning approach to synthesize hybrid LaCoO3 perovskite nanoparticles@nitrogen-doped carbon nanofibers (LCNP@NCNF) as an effective and robust electrocatalyst for Zn-air batteries. LCNP@NCNF featured an integrated structure with well-crystallized perovskite nanoparticles uniformly distributed in micro/mesoporous NCNF. In addition, LCNP@NCNF exhibited a high specific surface area of ~183.3 m2 g−1 and a large pore volume of ~0.164 m3 g−1. The rotating-electrode measurement revealed the better intrinsic activity and more favorable stability of LCNP@NCNF in comparison with their counterparts. Moreover, Zn-air batteries employing LCNP@NCNF showed a relatively smaller discharge-charge voltage gap of ~0.95 V and longer cycling stability than the battery adopting the physically blended LCNP and NCNF. We ascribed the improved electrochemical activity to the enhanced synergistic interaction originating from the successful coupling of LCNP and NCNF.

Oxy-fuel combustion power systems can utilize the cold energy released during the liquefied natural gas (LNG) regasification to reduce the power consumption of CO2 capture, but the specific LNG cold energy consumption of CO2 capture is still too large. To recover more CO2 with the limited LNG cold energy at a low energy cost, a novel natural gas-fired oxy-fuel power system with the cascade utilization of LNG cold energy is proposed in this work, where the LNG cold energy could be sequentially utilized in the air separation unit and the CO2 recovery process. The new system is evaluated with the Aspen Plus software. The results show that the net electrical efficiency and the specific primary energy consumption for CO2 avoided (SPECCA) of the new system are comparable to those of the chemical looping combustion cycle, and superior to those of the conventional O2/CO2 cycles. Moreover, the specific LNG needed for CO2 avoided (SLNCC) of the new system is more than 67.2% lower than the existing oxy-fuel power systems utilizing the LNG cold energy. Furthermore, it is found that the O2 purity of 97.0 mol.% and the CO2 capture ratio of 97.0% are optimal conditions, because the SPECCA, the specific exergy consumption for CO2 avoided (SECCA) and the SLNCC are at the minimum of 1.87 $${\rm{G}}{{\rm{J}}_{LHV}} \cdot {{\rm{t}}_{{\rm{C}}{{\rm{O}}_2}}}^{- 1},2.60\,\,{\rm{GJ}} \cdot {{\rm{t}}_{{\rm{C}}{{\rm{O}}_2}}}^{- 1}$$ and $$1.88\,\,{{\rm{t}}_{{\rm{LNG}}}} \cdot {{\rm{t}}_{{\rm{C}}{{\rm{O}}_2}}}^{- 1}$$ , respectively. Meanwhile, the net electrical efficiency and the exergy efficiency of the new system reach 51.51% and 49.23%, respectively.

Developing supercapacitors with simultaneous superior power and energy density for energy-storage devices remains a challenge. In this work, single-phase NiS2 microflowers were synthesized through ...

Liquid organic electrolytes commonly employed in commercial Li-ion batteries suffer from safety issues such as flammability and explosions. Replacing liquid electrolytes with nonflammable electrolytes has become increasingly attractive in the development of safe, high-energy Li-metal batteries (LMBs). In this work, nonflammable, robust, and flexible composite polymer-polymer electrolytes (PPEs) were successfully fabricated by flame-retardant solution casting with polyimide (PI) and polyvinylidene fluoride (PVDF). The optimized nonflammable PPEs (e.g., PPE-50) demonstrate not only good mechanical properties (i.e., a high tensile strength of 29.6 MPa with an elongation at break of 87.2%), but also high Li salts dissolubility, the former of which ensures the suppression of Li dendrites, while the latter further improves the ionic conductivity (∼1.86 × 10

Perovskite oxides are intriguing electrocatalysts for the oxygen evolution reaction, but both surface (e.g., composition) and bulk (e.g., lattice oxygen) properties should be optimized to maximize their participation in offering favorable activity and durability. In this work, it is demonstrated that through introducing exogenous Fe

In this work, we proposed a feasible approach to prepare multifunctional composite films by introducing a nanoscaled filler into a polymer matrix. Specifically, thanks to isophorone diisocyanate (IPDI) acting as a coupling agent, the hydroxyl groups and carboxyl groups on the surface of graphene oxide (GO) and the hydroxyl groups on the surface of silver-coated zinc oxide nanoparticles (Ag/ZnO) are covalently grafted, forming GO–IPDI–Ag/ZnO (AGO). The prepared AGO was then introduced into the hydroxypropyl cellulose (HPC) matrix to form AGO@HPC nanocomposite films by solution blending. AGO@HPC nanocomposite films exhibited improved mechanical, anti-ultraviolet, and antibacterial properties. Specifically, a tensile test showed that the tensile strength of the prepared AGO@HPC nanocomposite film with the addition of as low as 0.5 wt % AGO was increased by about 16.2% compared with that of the pure HPC film. In addition, AGO@HPC nanocomposite films showed a strong ultraviolet resistance and could effectively inactivate both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria at a low loading of AGO, and rapid sterilization plays a crucial role in wound-healing. In vivo results show that the AGO@HPC release of Ag+ and Zn2+ stimulates the immune function to produce a large number of white blood cells and neutrophils, thereby producing the synergistic antibacterial effects and accelerated wound-healing. Therefore, our results suggest that these novel AGO@HPC nanocomposite films with improved mechanical, anti-ultraviolet, and antibacterial properties could be promising candidates for antibacterial packaging, biological wound-dressing, etc. The abuse of antibiotics has brought about serious drug-resistant bacteria, and our nanofilm antibacterial does not entail such problems. In addition, local administration reduces the possibility of changing the body’s immune system and organ toxicity, which greatly increases the safety.

In this work, we successfully demonstrate that a crystal-structure regulation by simply altering the annealing temperature might be an effective way to enhance the electrocatalytic activity of perovskite oxides. We report a high-performance electrocatalyst with an orthorhombic double perovskite structure (i.e., PrBaCo2O5+δ, δ = ∼0.52), which shows superior activity and durability towards hydrogen evolution reaction in comparison to a cubic perovskite oxide (i.e., Pr0.5Ba0.5CoO3-δ) and a tetragonal one (i.e., PrBaCo2O5+δ, δ = ∼0.76), despite the similar composition. The improvement of the electrocatalytic activity for hydrogen evolution reaction is mainly attributed to a high-degree structure distortion resulted from the high oxygen vacancy concentration, a large electrochemical active surface area, and a low charge transfer resistance. In addition, lattice oxygen species may provide an extra contribution to the enhancement of the hydrogen evolution reaction for Pr0.5Ba0.5CoO3-δ sintered at 1000 °C. Furthermore, a considerable correlation between O p-band centers and HER overpotentials is observed, and PBC-1100 with the highest O p-band center exhibits the best HER activity. These results indicate that the electrochemical performance of perovskite oxides could be effectively enhanced. Especially orthorhombic double perovskite oxides could be a new class of promising electrocatalysts.

Electrocatalysts are the most compelling objectives in realizing highly efficient renewable energy conversion and storage applications. Rational doping is an effective strategy for the development of cost-effective perovskite oxides with high electrochemical performance. In this study, we report facilely prepared molybdenum (Mo)-doped SrCo0.70Fe0.30O3-δ perovskites such as SrCo0.7Fe0.25Mo0.05O3-δ (SCFM0.05) and SrCo0.7Fe0.20Mo0.10O3-δ (SCFM0.10) for boosting the hydrogen evolution reaction (HER) activity and stability. Among them, SCFM0.05 delivers a promising overpotential of ∼323 mV at the current density of 10 mA cmdisk^-2 and keeps almost stable for 5 h and after accelerated 1000 cycles. The promoted HER activity of SCFM0.05 regarding the decreased overpotential, increased catalytic current density, and improved charge transfer kinetics, might originate from the combined effects of distortion of octahedral coordination, low oxygen vacancy/high oxidation state of Co, abundant lattice oxygen and highly oxidative oxygen species, long B–O length, and strong OH− adsorption compared to the un-doped counterpart. We ascribe the enhanced operational stability to the formation of a low concentration of oxygen vacancy that stabilizes the crystal structure of Mo-doped SrCo0.7Fe0.3O3-δ and prevents the surface from Sr leaching/surface amorphization. These findings suggest that tuning perovskite oxide using a redox-inactive dopant featured with high valence state may provide further avenues to HER optimization. This research is supported by the National Natural Science Foundation of China (No. 51702125 & No. 21808080), Pearl River S&T Nova Program of Guangzhou (No. 201806010054), Fundamental Research Funds for the Central Universities (No. 21616301), and the China Postdoctoral Science Foundation (No. 2017M620401).

Solid polymer electrolytes have great potentials to overcome safety issues of organic liquid electrolytes for lithium-ion batteries (LIBs). However, the poor lithium-ion migration within solid polymers impedes the broad applications. In this work, composite polymer electrolytes (CPEs) are prepared by dispersing oxygen-ion conducting Sm-doped CeO2 (SDC) nanowires into the polyvinylidene fluoride matrix. The ionic conductivity and the lithium-ion transfer number are greatly enhanced after the introduction of the SDC nanowires to CPEs, thanks to the increase of amorphous regions resulted from the SDC filler, the Lewis acid-base interaction due to the positively charged oxygen vacancies, and the partial dehydrofluorination. Specifically, CPE-10 with 10 wt% of the SDC nanowires reaches the ionic conductivity of 9.09 × 10−5 S cm−1 at 30 °C with a lithium-ion transfer number of ∼0.40. Also, CPE-10 exhibits a relatively high oxidation potential of 4.89 V versus Li+/Li. Impressively, a quasi-solid-state CR2032 LiFePO4/CPE-10-20 μL/Li battery exhibits the initial capacity of as high as 155.1 mAh g−1 at 1 C, and it still delivers 155.3 mAh g−1 after 130 cycles, as well as the favorable rate performance (e.g., 135.1 mAh g−1 at 4 C). Besides, a lithium-oxygen battery (Super P/CPE-10-5 wt% LiI/Li) exhibits the initial discharge capacity of 5325 m A h g c a r b o n - 1 with the coulombic efficiency of 85.7%. Our work demonstrates that CPEs with the oxygen-ion conducting SDC nanowires could be potentially applied in quasi-solid-state LIBs and lithium-oxygen batteries.

In this work, we have prepared the carbon-LiNi1/3Co1/3Mn1/3O2 composite through a simple and cost-effective method at a relatively low temperature (i.e., 180 °C) via spray drying. Nitric acid-treated commercial Super P powder could be well dispersed among LiNi1/3Co1/3Mn1/3O2 particles, while untreated Super P powder is particularly difficult to be uniformly distributed. The obtained I(003)/I(104) of the treated Super P-LiNi1/3Co1/3Mn1/3O2, according to the X-ray diffraction pattern, is higher than 1.70, suggesting that the highly ordered structure of LiNi1/3Co1/3Mn1/3O2 is maintained after compositing via the proposed approach. The resulted cathode material shows superior rate capability and stability, delivering a specific capacity of 115.7 mAh g−1 even at 1.5 A g−1, and a capacity retention of 87.0% after 500 cycles. In contrast, pure LiNi1/3Co1/3Mn1/3O2 delivers only 57.4 mAh g−1 at 1.5 A g−1 and remains 35.2% after 500 cycles. Carbon-coated LiNi1/3Co1/3Mn1/3O2 prepared from the carbonization of sucrose delivers as high as 141.0 mAh g−1 at 0.1 A g−1, but remains only 47.5% after 100 cycles. The enhancement of rate capability and stability from the treated Super P-LiNi1/3Co1/3Mn1/3O2 is due to the facilitation of the electron conduction by introducing homogenously distributed carbon, and thanks to the well-maintained ordered structure of LiNi1/3Co1/3Mn1/3O2.

Perovskite LaMnO3 is reported to be a superior electrocatalyst for oxygen reduction reaction in terms of the onset potential and intrinsic activity. However, traditionally prepared LaMnO3 is characterized to exhibit a low specific surface area and a limited pore volume. Herein, we synthesize a three-dimensional ordered macroporous LaMnO3 that features ordered and interconnected porous structure, in order to increase catalytic sites. The obtained three-dimensional ordered macroporous LaMnO3 exhibits an increased specific surface area of 20.328 m2 g−1 and pore volume of 0.126 cm3 g−1. Rotating-ring-disk electrode measurement reveals a more positive onset potential (0.827 V) and half-wave potential (0.686 V), and a much higher current-limited density (5.90 mA cm−2) of the three-dimensional ordered macroporous LaMnO3 compared to counterparts, as well as a high electron transfer number (∼4) and a better stability. Furthermore, a Li O2 battery employing the three-dimensional ordered macroporous LaMnO3 as air electrode exhibits excellent electrochemical performance with a higher initial discharge capacity (5592 mAh g−1), a smaller discharge-charge voltage gap (1.56 V), and a higher coulombic efficiency (∼100%) in comparison with the carbon electrode. Our results suggest that traditional perovskite oxides could be effectively optimized for efficient electrocatalytic reactions.

Herein we report Co3O4/Co@N-doped carbon nanotubes (T-Co3O4/Co@NC) as an efficient and highly stable anode material for lithium-ion batteries. T-Co3O4/Co@NC is facilely prepared via the thermal decomposition of Co3[Co(CN)6]2 in N2 and the oxidation in O2. T-Co3O4/Co@NC exhibits a high degree of graphitization and a large specific surface area, thus promoting the conductivity and providing more active sites. More importantly, the proper existence of metallic Co makes the reaction more reversible and thus leading to the improved cycling stability. Specifically, T-Co3O4/Co@NC delivers a high specific capacity of 689.2 mAh g−1 at 500 mA g−1 after 400 cycles with the capacity retention rate of 99.5%. In contrast, Co3O4/Co@N-doped carbon nanoball (B-Co3O4/Co@NC) exhibits a discharge specific capacity of only 247.0 mAh g−1 after 400 cycles, and the capacity retention rate is as low as 30.1%. Furthermore, T-Co3O4/Co@NC also exhibits excellent cycling performance in a full cell, with the coulombic efficiency over 95%, capacity retention rate over 87% after 100 cycles. The improved stability is mainly attributed to the existence of metallic Co which helps to optimize the solid electrolyte interphase film and form carbon nanotubes.

In this work, we report the silver doping as a novel strategy for developing single-phase mixed conducting ceramic membranes with perovskite-type structure for the efficient oxygen separation from air. Specifically, perovskite-type oxide with a nominal composition of Sr0.95Ag0.05Co0.9Nb0.1O3-δ (SANC) was designed, synthesized and investigated, and a comparative study with the Ag-free SrCo0.9Nb0.1O3-δ (SNC) perovskite-type membrane was also conducted. The incorporation of silver into the perovskite lattice of SNC has been confirmed even after the sintering at 1175 °C using Ag2O as the silver source. An improved sintering feature, enhanced mechanical strength, and an increased electrical conductivity of the SANC membrane when compared to the Ag-free SNC have been observed. Furthermore the chemical bulk diffusion and surface exchange coefficients increased through the silver doping. Above all higher oxygen permeation fluxes were achieved for the SANC membrane when compared with the SNC membrane under the corresponding conditions. Therefore, SANC turned out to be a highly promising ceramic membrane material for oxygen separation.

Sluggish oxygen reduction reaction (ORR) kinetics and chemical instability of cathode materials hinder the practical application of solid oxide fuel cells (SOFCs). Here we report a Co-free Hf-doped SrFe0.9Hf0.1O3−δ (SFHf) perovskite oxide as a potential cathode focusing on enhancing the ORR activity and chemical stability. We find that SFHf exhibits a high ORR activity, stable cubic crystal structure, and improved chemical stability toward CO2 poisoning compared to undoped SrFeO3−δ. The SFHf cathode has a polarization area-specific resistance as low as 0.193 Ω cm2 at 600 °C in a SFHf|Sm0.2Ce0.8O1.9 (SDC)|SFHf symmetrical cell and has a maximum power density as high as 1.94 W cm–2 at 700 °C in an anode-supported fuel cell (Ni+(ZrO2)0.92(Y2O3)0.08 (YSZ)|YSZ|SDC|SFHf). The ORR activity maintains stable for a period of 120 h in air and in CO2-containing atmosphere. The attractive ORR activity is attributed to the moderate concentration of oxygen vacancy and electrical conductivity, as well as the fast oxygen ...

Highly active bifunctional catalysts for oxygen evolution reaction (OER) and oxygen reduction reactions (ORR) have attracted increasing attention in metal-air batteries and fuel cells. CoFe nanoalloy particles encapsulated in nitrogen-doped carbon and nitrogen-doped carbon nanotubes (CoFe@NC-NCNT-H) are synthesized by pyrolyzing a Prussian blue analogue precursor (i.e. Fe3[Co(CN)6]2) as low as 600 °C, and followed by HNO3 treatment. Such low temperature pyrolysis and HNO3 treatment affords the hybrid mesoporous material with a high level of nitrogen content (∼10%) and a relatively high specific surface area (∼210.5 m2 g−1), capable of providing active sites and mass transport channels. In alkaline solution, CoFe@NC-NCNT-H is highly active towards OER with a low onset potential (∼1.35 V) and a small overpotential (∼380 mV) to reach 10.0 mA cm−2, comparable to the state-of-the-art RuO2. CoFe@NC-NCNT-H is also a good ORR catalyst, and more importantly it exhibits an improved stability compared to commercial Pt/C. CoFe@NC-NCNT-H displays promise as a bifunctional catalyst with an extremely low potential difference (∼0.87 V between ORR at −3.0 mA cm−2 and OER at 10.0 mA cm−2), superior to commercial Pt/C and RuO2. The facilely prepared CoFe@NC-NCNT-H with high bifunctional performance and stability promises great potential for ORR and OER.

Mankind has witnessed a dramatically growing challenge regarding water pollution during the past decades. Meanwhile, intensive attention has been paid to developing functional materials which can comprehensively treat wastewater which always includes bacteria, organic and inorganic contaminants. In this work, a reduced graphene oxide and montmorillonite composite (rGO–MMT) aerogel was synthesized by a one-step green method to treat multiple pollutants in wastewater. The Langmuir isotherm model and the pseudo-second-order kinetic model were well fitted to the adsorption of both dyes and heavy metal ions. The rGO–MMT aerogel exhibited 97.31% and 94.87% removal efficiencies for methylene blue (MB) and Cr(VI), respectively. In addition, the antibacterial ratios of the rGO–MMT loaded with quaternary ammonium salt reached 91.57% and 95.53% for E. coli and S. aureus, respectively. Our results demonstrated that the aerogel had a high multi-component adsorption capacity and antibacterial activity. Attractively, the rGO–MMT aerogel exhibited excellent recyclable properties thanks to its special three-dimensional structure with outstanding mechanical strength.

The rational design of highly active and durable electrocatalysts for overall water splitting is a formidable challenge. In this work, a double perovskite oxide, i.e., NdBaMn2O5.5, is proposed as a bifunctional electrode material for water electrolysis. Layered NdBaMn2O5.5 demonstrates significant improvement in catalyzing oxygen and hydrogen evolution reactions (OER and HER, respectively), in contrast to other related materials, including disordered Nd0.5Ba0.5MnO3−δ as well as NdBaMn2O5.5−δ and NdBaMn2O5.5+δ (δ 1.75 V) and catalytic durability in comparison to those of Pt/C–RuO2, making it a promising candidate electrode material for water electrolyzers. The substantially enhanced performance is attributed t...

A high efficient visible-light-region Cu 2 O/g-C 3 N 4 /RGO composite 3D aerogel photocatalyst was fabricated by a facile self-assemble method. The aerogel composite with various RGO and g-C 3 N 4 to Cu 2 O weight ratios was synthesized and characterized. The results showed that the Cu 2 O/g-C 3 N 4 heterojunction absorbed visible light region shifted to a lower energy. In order to improved photocatalytic activity, the Cu 2 O/g-C 3 N 4 heterojunction loaded on reduced graphene oxide sheets resulted in increasing absorption in the visible light range and improving photodegradation activity. The optimal content of Cu 2 O in the Cu 2 O/g-C 3 N 4 /RGO aerogel was 40%, which exhibited the effectively synthetized Cu 2 O/g-C 3 N 4 heterojunction, and greatly improved photocatalytic activity. Moreover, the ternary composite aerogel exhibited 96% (Methylene Blue) and 83% (Methyl Orange) degradation efficiency within 80 min. The combined heterojunction with synergistic effects of this novel composite aerogel account for the excellent photocatalytic efficiency.

Double perovskite oxides, such as PrBaCo2O5+δ (PBC), are among the most promising cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) thanks to their high catalytic activity and mixed ionic and electronic conductivity. Here, we investigate the impact of Nb substitution on the crystal structure, catalytic activity, and electrical conductivity of PBC. Several studies have outlined that doping high valence cations, such as Nb5+, effectively stabilizes the perovskite structure, decreases the thermochemical expansion coefficient of the material, and can benefit the peak power density of the fuel cell. The as-prepared PrBaCo2−xNbxO5+δ with x = 0, 0.25, 0.50, 0.75, and 1.00 (PBCN) exhibit structural change from P4/mmm (x = 0) to I4/mmm (x = 1), whereas both phases are present for intermediate compositions. The analysis of electrochemical impedance spectroscopy (EIS) data shows that PBCN is characterized by relatively low polarization resistance. Between 300 and 800 °C, the electrical conductivity of PBCN, with x = 0.25, 0.50, lies above 100 S cm−1. If x = 0.75 or 1.00, the conductivity drops below 100 S cm−1. Our work suggests that the Nb-doped PBC exhibits excellent chemical compatibility with typical electrolyte material and good electrochemical performance, making it a promising cathode material for applications in IT-SOFCs.

Most perovskites possessing high oxygen permeability always suffer from low chemical stability under CO2-containing conditions. A comprehensive knowledge for improving the resistance toward CO2 through doping strategy is still lacking. In this work, we propose a series of perovskite oxides, i.e., SrFe0.8M0.2O3−δ (M=Ti4+, Nb5+, and Cr6+), and systematically investigate the effect of dopants with the high oxidation state on the phase structure, chemical stability, sintering behavior, conducting properties, and oxygen permeability. The oxygen permeability and the CO2 tolerance of the membranes are closely related to the oxidation state of the dopants for altering the oxygen vacancy concentration, the oxidation state of Fe ions and the average metal-oxygen bond energy. The balance of oxygen permeability and the CO2 tolerance should be taken into account during practical application. This work thus provides useful guidelines for the future development of perovskite oxides through B-site doping for efficient air separation.

Nonstoichiometric perovskites with active metal nanoparticles exsolved on the surface have shown promising potential in energy and environmental applications ranging from catalysis to power generation. In this work, a novel Sc-based A-site deficient perovskite material La 0.4 Sr 0.4 Sc 0.9 Ni 0.1 O 3−δ (LSSN) is reported as a highly active anode for intermediate-temperature solid oxide fuel cells. The material is designed using both thermodynamical analysis and ab-initio simulations. The drop in Gibbs free energy for Ni in H 2 is substantial in comparison to the other elements, and density functional theory simulations indicate that the segregation of Ni towards the surface is energetically favored. Spherical Ni nanoparticles with well-defined boundaries are exsolved on the surface of LSSN after reduction in hydrogen, and the reduced samples show a high electrochemical catalytic activity in symmetric-cell measurements with an area specific resistance as low as 0.055 Ω cm 2 at 800 °C in humid H 2 . Insights into the exsolution mechanism are also derived from both experiments and analytical modeling. Experimental observations show a patterned particle distribution, which is consistent with heterogeneous nucleation. The particle size evolution is investigated using the strain, reactant, and diffusion limited analytical models. The mechanistic insights gained here can be broadly applied to design more efficient materials capable of exsolution and to control the nanoparticle growth and coverage.

The B-site substitution with the minor amount of tin in BaFeO3−δ parent oxide is expected to stabilize a single perovskite lattice structure. In this study, a composition of BaFe0·95Sn0·05O3−δ (BFS) as a new cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs) is synthesized and characterized. Special attention is paid to the exploration of some basic properties including phase structure, oxygen non-stoichiometry, electrical conductivity, oxygen bulk diffusion coefficient, and surface exchange coefficient, which are of significant importance to the electrochemical activity of cathode materials. BFS holds a single cubic perovskite structure over temperature range of cell operation, determined by in-situ X-ray diffraction and scanning transmission electron microscope. A high oxygen vacancy concentration at cell operating temperatures is observed by combining thermo-gravimetric data and iodometric titration result. Furthermore, electrical conductivity relaxation measurement illustrates the fast oxygen bulk diffusion and surface exchange kinetics. Accordingly, testing cells based on BFS cathode material demonstrate the low polarization resistance of 0.033 Ω cm2 and high peak power density of 1033 mW cm−2 at 700 °C, as well as a relatively stable long-term operation for ∼300 h. The results obtained suggest that BFS perovskite oxide holds a great promise as an oxygen reduction electrocatalyst for IT-SOFCs.

We report Ba0·95Ca0·05Fe0·95In0·05O3−δ (BCFI), a novel cobalt-free perovskite, as a promising cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). We synthesize this new material, and systematically characterize its lattice structure, thermal stability, chemical composition, electrical conductivity, and oxygen reduction reaction (ORR) activity. The cubic phase of BaFeO3−δ is stabilized by light isovalent and lower-valence substitution, i.e., 5% Ca2+ in the Ba2+ site and 5% In3+ in the Fe3+/Fe4+ site, in contrast with the typical approach of substituting elements of higher valence. Without resorting to co-doping strategy, the phase of BaFe0·95In0·05O3−δ (BFI) is rhombohedral, while Ba0·95Ca0·05FeO3−δ (BCF) is a mixture of the cubic phase together with BaFe2O4 impurities. The structure of BCFI is cubic from room temperature up to 900 °C with a moderate thermal expansion coefficient of 23.2 × 10−6 K−1. Thanks to the large oxygen vacancy concentration and fast oxygen mobility, BCFI exhibits a favorable ORR activity, i.e., we observe a polarization resistance as small as 0.038 Ω cm2 at 700 °C. The significantly enhanced performance, compared with BFI and BCF, is attributed to the presence of the cubic phase and the large oxygen vacancies brought by the isovalent substitution in the A-site and lower-valence doping in the B-site.

Developing cost-effective oxygen electrocatalysts is critical to the wide application of renewable energy technologies including fuel cells, electrolyzers, and metal-air batteries. In this work, we report Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ (BSCF) on nitrogen-doped mesoporous carbon (NC) as a novel and highly-active bi-functional catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The NC is prepared using organic waste, namely banana peels. The carbonization, heteroatom doping, and surface functionalization are achieved simultaneously during a facile synthesis process. The obtained NC is characterized by large mesopores with a specific surface area of 457.6 m 2 g −1 . The electrochemical measurements reveal that, the current density of the BSCF/NC in 0.1 mol L −1 KOH reaches −3 mA cm −2 at 0.74 V and 10 mA cm −2 at 1.58 V vs. the reversible hydrogen electrode. Furthermore, the hybrid shows a smaller onset potential and larger current density towards both ORR and OER in comparison to composites made of BSCF and common commercial carbon supports, including acetylene black (AB) carbon, activated carbon (AC), and Vulcan XC-72 carbon. Besides enhancing the surface area and the dispersion of BSCF, the electronic interaction between BSCF and NC likely renders the enhanced activity.

Egg yolk-derived P and N dual doped nano carbon capsules (PNCCs) have been synthesized and used as lithium ion battery anodes. The application of egg yolk as the carbon source is a new and environmental-friendly approach for biomass recycling. The reversible capacity of half cells made of PNCCs is as high as ~770 mA h g−1 at a current density of 0.5 A g−1 with considerable rate capacity and cycling stability. PNCCs show a capsule-like structure, which provide extra edges and active sites for lithium intercalation. The heteroatom doping also introduce defects and disorder, which increases the electrochemical activity and creates more active sites for lithium insertion.

The development of energy conversion and storage devices and the disposal of solid waste represent two major challenges for environmental sustainability. The development of many key sustainable energy technologies relies on fast oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics. However, both reactions are sluggish. In the present work, we address these two issues synergistically by fabricating Fe2O3 wrapped in P and S dual-doped graphitized carbon (Fe2O3/P–S-CG) from soiled baby diapers, whose disposal and recycling are beneficial to the environment. Electrochemical tests revealed that Fe2O3/P–S-GC has a significant catalytic activity towards both the ORR and OER in 0.1 M KOH. In particular, the difference between the ORR potential at 3 mA cm−2 and the OER potential at 10 mA cm−2 is as small as ∼0.86 V. This value is comparable to that of commercial precious metal-based catalysts. In addition, Fe2O3/P–S-GC exhibits a favorable catalytic durability, making it a promising bi-functional non-precious catalyst for the ORR and OER.

The simultaneous high oxygen permeability and high chemical stability of perovskites for use as oxygen transport membranes are of critical importance for applications in oxyfuel processes and as membrane reactors for coupling reactions. Here cobalt-free and CO2-tolerant SrFe0.8M0.2O3−δ (M=Zr, Mo, and W) were exploited as materials for oxygen transport membranes, which exhibited stable cubic phase structures in both air and CO2-containing atmospheres. At 850 °C and under the air/helium gradient across the membranes, oxygen permeation fluxes of 0.387, 0.216 and 0.201 mL cm−2 min−1 [STP] were reached for SrFe0.8Zr0.2O3−δ, SrFe0.8Mo0.2O3−δ and SrFe0.8W0.2O3−δ (membrane thickness: 1 mm), respectively. More importantly, relatively stable oxygen permeation fluxes of 0.262, 0.145 and 0.164 mL cm−2 min−1 were still reached for above three membranes correspondingly and maintained for almost 600 min when the sweep gas was switched to 10% CO2-containing helium when compared to the un-doped SrFeO3−δ membrane. Our findings suggest that the stable phase structure and improved CO2 resistance can be effectively achieved by facile doping of high-valence and redox-inactive transition metal ions into the SrFeO3−δ parent oxide. This process provides an efficient way for the development of CO2-tolerant oxygen transport membranes without applying other complex membrane structures (e.g., dual-phase membranes) or noble metals.

This work systematically investigates the effects of single A-site dopant (5 mol% La3+, Sm3+ and Gd3+) and single B-site dopant (5 mol% Zr4+ and Ce4+) on the structure and oxygen reduction reaction of BaFeO3−δ (BFO) used as a cathode for solid oxide fuel cells. The materials are prepared by solid-state method and their structural, electronic, electrocatalytic properties are characterized and compared. X-ray diffraction reveals 5 mol% A-site or B-site dopant is sufficient to stabilize the cubic phase of BFO, as predicted by the lattice calculation. X-ray photoelectron spectroscopy and iodometric titration demonstrates that neither of the two doping sites has obvious advantage over the other towards the formation of additional oxygen vacancies. B-site doped BFO shows a lower electrical conductivity than A-site doped ones, however, they have much quicker response to electrical conductivity relaxation, likely originating from the expanded lattice size. With the largest oxygen vacancy concentrations, Ba0.95La0.05FeO3−δ and BaFe0.95Zr0.05O3−δ stand out from the A-site and B-site doped BFO, respectively, and polarization resistances of 0.029 Ω cm2 and 0.020 Ω cm2 are achieved at 700 °C, P O 2 = 0.2 atm . With a similar amount of oxygen vacancies, B-site doping is more advantageous for enhancing oxygen bulk diffusion kinetics, and thus ORR activity.

Low cost materials with high electrochemical catalytic activity for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are in urgent demand for energy storage and conversion devices. In this work, we propose a novel and environmentally-friendly approach to synthesize in situ a meso-porous MnO x /S doped graphitized carbon (MnO x /S-GC) hybrid with a specific surface area of 502.6 m 2 g −1 . The synthesis involves the thermal treatment of polyvinyl chloride (PVC) together with KMnO 4 and (NH 4 ) 2 Fe(SO 4 ) 2 . It is the first time a MnO x /S-GC hybrid is fabricated directly from a carbon source without any intermediate products such as graphene oxide or additional chemical reagents. In addition, since PVC is the major component of plastics, this method has provided a new approach for the utilization of waste. Most importantly, the as-prepared hybrid showed a high catalytic activity towards both ORR and OER. The current density reached −3 mA cm −2 at 0.81 V and 10 mA cm −2 at 1.62 V vs. reversible hydrogen electrode respectively.

SrNb0.1Co0.9O3−δ (SNC) thin films prepared on single-crystal yttria-stabilized zirconia (YSZ) electrolytes are evaluated as promising cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Geometrically well-defined polycrystalline SNC thin films with low surface roughness and high surface oxygen vacancy concentration are successfully fabricated by pulsed laser deposition. The thin films are characterized by basic techniques, e.g., X-ray diffraction for phase structure identification, scanning electron microscopy and atomic force microscopy for microstructures measurement, and X-ray photoelectron spectroscopy for elements quantification. Electrochemical impedance spectroscopy (EIS) is used to investigate oxygen reduction reaction activities of SNC thin films in symmetric electrochemical cells. Current collectors (Ag paste, Ag strip, and Au strip) are found to have negligible impact on polarization resistances. A slight decrease of the electrode polarization resistances is observed after adding a samarium doped ceria (SDC) buffer layer between SNC and YSZ. SNC thin-film electrodes exhibit low electrode polarization resistances, e.g., 0.237 Ω cm2 (SNC/SDC/YSZ/SDC/SNC) and 0.274 Ω cm2 (SNC/YSZ/SNC) at 700 °C and 0.21 atm, demonstrating the promise of SNC materials for IT-SOFCs. An oxygen reduction reaction mechanism of SNC thin films is also derived by analyzing EIS at temperature of 550–700 °C under oxygen partial pressure range of 0.04–1 atm.

Solid-state Li-metal batteries are promising as next-generation energy storage devices. However, the main bottlenecks are the poor conductivity of the solid electrolyte and the high interfacial resistance. While polymers exhibit a lower interfacial resistance in comparison to ceramics, they often require the inclusion of flammable solvents. In this work, highly conductive composite polymer electrolyte (CPE) membranes are prepared by integrating a poly(vinylidene fluoride) matrix (PVDF) with a Li-conductive perovskite (i.e., Li0.38Sr0.44Ta0.70Hf0.30O2.95F0.05, LSTHF), a flame-retarding solvent (i.e., trimethyl phosphate (TMP)), and a Li salt (i.e., LiClO4). The CPE membrane with 10 wt% LSTHF (CPE-10) exhibits conductivities as high as 0.53 mS cm−1 at room temperature (RT) and 0.36 mS cm−1 at 0 °C. Furthermore, prototype batteries, including the CPE-10 electrolyte, show high initial discharge capacities, good rate capabilities, and stable cycling performance at either RT or 5 and 60 °C. This study illustrates that including a Li-conductive perovskite and TMP in a PVDF-based polymer material could yield safe, high-performance quasi-solid-state Li-metal batteries capable of operating over a relatively wide temperature range.

Developing cost-effective and efficient bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of considerable importance for fuel cells and metal-air batteries. In this work, a non-precious composite (i.e., Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF), g-C3N4 and Vulcan carbon (VC)) labeled as BSCF/g–C3N4–VC was developed via ultrasonically mixing. The formed BSCF/g–C3N4–VC exhibited improved ORR and OER activity compared with the individual g-C3N4 and BSCF, as well as the composites of g–C3N4–VC and BSCF/VC. The critical roles of BSCF, g-C3N4, and VC for boosting ORR and OER have been clearly demonstrated. Apparently, the prepared composite overcame major limitations of perovskite-type BSCF and g-C3N4, i.e., the relatively low specific surface area (~0.27 ​m2 ​g−1) of the former and the extremely low electronic conductivity of the latter. Moreover, the significantly enhanced electrocatalytic activity could be attributed to the synergistic effect between g-C3N4, BSCF, and VC. Our results suggest that facilely compositing carbon materials (e.g. VC and g-C3N4) with perovskite-type oxides (e.g. BSCF) will open a new path for the development of highly efficient oxygen electrocatalysts.

Solid composite electrolytes have gained increased attention, thanks to the improved safety, the prolonged service life, and the effective suppression on the lithium dendrites. However, a low ionic conductivity (

BaZrxCeyY1-x-yO3-δ are recognized proton-conducting electrolyte materials for proton-conducting solid oxide fuel cells (H+-SOFCs) below 650 °C. Here Co cations are incorporated into the BaZr0.4Ce0.4Y0.2O3-δ (BZCY) scaffold to generate a 3D core-shell and triple-conducting (H+/O2−/e−) electrode in situ via infiltrating and reactive sintering. The core is the bulk BZCY scaffold, while the shell is composed of the cubic Ba(Zr0.4Ce0.4Y0.2)1-xCoxO3-δ, cubic spinel Co3O4 and cubic fluorite (Ce, Zr, Y)O2. The obtained electrode exhibits an excellent compatibility with the BZCY electrolyte, and performs well in yielding a low and stable polarization resistance for oxygen reduction reaction for intermediate-temperature H+-SOFCs. In particular, it achieves polarization resistances as low as 0.094 and 0.198 Ω cm2 at 650 and 600 °C in wet air (3% H2O) when the sintering temperature for the electrode is 900 °C. In addition, a symmetrical cell also exhibits operation stability of 70 h at 650 °C. Furthermore, a fuel cell assembled with the 3D core-shell and triple-conducting electrode delivers a peak power density of ∼330 mW cm−2 at 650 °C. The substantially improved electrochemical performance and high stability are ascribed to the unique core-shell structure and the formation of Ba(Zr0.4Ce0.4Y0.2)1-xCoxO3-δ in the shell. Accepted version

Oxygen evolution reaction (OER) is critical to many important energy conversion and storage processes. However, the kinetics of OER is typically sluggish, and conventional OER catalysts are scarce and expensive. Hence, inexpensive and effective catalysts that accelerate the OER kinetics and reduce the overpotential are urgently needed. In this paper, we reported multi-layer graphene-supported perovskite Ba0.95La0.05FeO3−δ (BLF–MLG) as a highly active OER catalyst. Electrochemical results showed that the BLF–MLG hybrid exhibited a high current density (∼23 mA/cm2 at 0.60 V vs. mercury/mercury oxide electrode (MMO)) and a more negative onset potential (∼0.43 V vs. MMO). Furthermore, the hybrid showed a smaller Tafel slope (77 mV/decade) and improved long-term stability. The remarkable OER performance is mainly attributed to the synergistic effect between BLF and graphene.

Oriented PrBaCo 2 O 5+δ (PBC) thin films are prepared on yttria-stabilized ZrO 2 (YSZ) substrates with orientations (001), (110) and (111) via pulsed laser deposition (PLD). Electrochemical impedance spectroscopy (EIS) experiments at various temperatures and oxygen partial pressures reveal a good oxygen reduction reaction (ORR) performance of all the thin films. However, the films' performance has considerable variance. PBC thin film deposited on (111) oriented YSZ had the best performance, followed by (110) and (001). Experiments including high resolution X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and computation, namely molecular dynamics (MD), are used to elucidate the substrate-determined orientations, examine the morphology and composition of the thin films, and to explain the variance of the ORR performance. Our results support the anisotropy of the oxygen vacancy pathway in the a–b plane and indicate that the substrate orientations can have great influence on the thin films properties.