Wide Operating Temperature Window Research Articles

Enhancing Oxygen Catalytic Performance in Zinc-Air Batteries through Localized Micro-Interface Reconstruction of Cobalt-Manganese Spinel

Reversible zinc-air batteries are widely regarded as one of the most promising candidates for clean energy conversion and storage technology owing to their cost-effectiveness, inherent safety, wide operating temperature window and high theoretical energy density.(1) In general, the performance of zinc-air batteries is heavily dependent on highly active bifunctional electrocatalysts, which effectively accelerate oxygen reduction/evolution reaction (ORR/OER) kinetics. Among various electrocatalysts for advanced air cathodes, multivalent Co3-xMnxO4±δ oxides, as the representative mixed transition metal spinel, have attracted widespread interest because of their O2 catalytic potential and diverse properties.(2) In comparison to the state-of-the-art Pt- and Ir-based catalysts, the catalytic performances of Co3-xMnxO4± δ remains constrained by its low electrical conductivity and inadequate ability to adsorb and activate O2.(3) Herein, we develop a unique pathway to achieve the self-reconstruction of the local micro-interface and electronic structure of Co3-xMnxO4±δ via a combustion reaction coupled with a high-temperature reduction process. The Co particles derived from the self-reconstructed Cox@Co1.5-xMn1.5O4-δ catalyst not only facilitate the formation of a metal/oxide heterojunction active interface but also improve the electrical conductivity. More importantly, Co metal precipitated from the tetrahedral site with high spin electronic configuration induces the transformation of lattice oxygen into oxygen vacancies, thereby effectively accelerating reactant adsorption. As expected, the Cox@Co1.5-xMn1.5O4-δ catalyst shows good ORR/OER activity with low overpotential. Furthermore, the zinc-air battery assembled by Cox@Co1.5-xMn1.5O4-δ catalyst demonstrates an extended charge-discharge lifespan exceeding 1000 hours, significantly surpassing that of the Pt/C+Ir/C catalyst (100 hours). The primary factor contributing to its high stability is the dimensional growth following catalyst reconstitution. This work offers novel insights into enhancing the small molecule electrocatalytic performance of typical mixed transition metal oxides, including spinel and perovskite catalysts.References A. Li, S. Kong, C. Guo, H. Ooka, K. Adachi, D. Hashizume, Q. Jiang, H. Han, J. Xiao and R. Nakamura, Nature Catalysis, 5, 109 (2022).N. Xu, Y. Zhang, M. Wang, X. Fan, T. Zhang, L. Peng, X.-D. Zhou and J. Qiao, Nano Energy, 65, 104021 (2019).C. Li, X. Han, F. Cheng, Y. Hu, C. Chen and J. Chen, Nature Communications, 6, 7345 (2015).

Construction of CuCoCe ternary catalyst via a porous organic polymer template approach for efficient CO-PROX with wide operating temperature window

Preferential CO oxidation (CO-PROX) is a promising approach for removing trace CO from hydrogen-rich streams, effectively preventing Pt anode poisoning in proton-exchange membrane fuel cells (PEMFCs). To effectively eliminate CO within the PEMFC operating temperature range, catalysts must exhibit high CO conversion and O2 selectivity. Expanding the operating temperature window of these catalysts is crucial. This study presents the synthesis of a CuCoCe ternary catalyst (CuCo/Ce-P) using an imidazole-functionalized porous organic polymer as a sacrificial template. Compared to the CuCoCe ternary catalyst prepared without a template (CuCo/Ce), CuCo/Ce-P exhibits significantly enhanced catalytic activity, with a T50 reduction from 85 °C to 55 °C and an expanded operating temperature window of approximately 40 ℃. Characterization results indicate that the imidazole-functionalized porous organic polymer facilitates improved dispersion of active species by anchoring metal ions through electron-rich groups, enhances intermetallic interactions, promotes electron transfer, and significantly improves the oxygen-deficient capacity of the CuCoCe ternary catalyst. Consequently, the catalyst exhibits a greater number of active interfaces, leading to enhanced catalytic activity and a wider operating temperature window.

A novel lanthanum ion-assisted fluorapatite precipitation approach for efficient fluoride removal from water

Excess amounts of fluoride ions (F-) in water/wastewater bring great hazards to human health and the environment. The traditional method such as precipitation by calcium ions does not work well for low-concentration F- removal. Herein, we developed a lanthanum ion (La3+)-assisted fluorapatite precipitation approach to treat F--containing water, aiming at high removal efficiency. Through an orthogonal experimental design and single-factor experiment, the optimized reaction conditions were obtained as the molar ratio of (Ca2++La3+): PO43-: F-=7.5: 4: 1, Ca2+: La3+ = 90: 10, and reaction pH of 9. Under such reaction conditions, F- in water (10 mg L−1) could be well controlled under 1 mg L−1, fulfilling relevant environmental standards. No remarkable F- removal efficiency loss was found in the presence of typical anions (e.g., halides, bicarbonate, sulfate). The developed F- removal approach also worked well in a wide F- concentration range (10–200 mg L−1) and reaction temperature range (5–45 °C). Further reaction mechanism study proved that the formation of LaFx(OH)3-x colloids was the key step, which could accumulate F- ions in water into colloids. The subsequently added Ca2+ and PO43- destroyed the stable colloids, and then promoted the formation of fluorapatite with simultaneous La3+ doping, which existed as precipitate and allowed the easy separation from the reaction solution. As a by-product, the as-produced La3+-doped fluorapatite was evaluated as an adsorbent for organic pollutant removal, which possessed a high adsorption capacity (763.4 mg g−1) for the model pollutant of Congo red. Considering the facile operation process, high F- removal efficiency, wide operation temperature window, and anti-inference for co-existing anions, the La3+-assisted fluorapatite precipitation approach possessed great potential for F--containing water/wastewater treatment.

Synergistic effect of platinum single atoms and nanoclusters for preferential oxidation of carbon monoxide in hydrogen-rich stream

Despite the maximum atom-utilization efficiency and remarkable activity of single-atom catalysts, further improvement of catalytic activity can be obtained by the synergistic effect of single atoms and nanoclusters in some catalytic systems. Herein, CeFeOx-supported Pt single atoms coupling with subnanometric clusters (Pt1-Ptn) structures are developed via a facile strategy. They are applied as the highly efficient catalysts for the preferential oxidation of CO in H2-rich stream (CO-PROX), which achieve complete elimination of CO at low temperature of 50 °C, with a wide operating temperature window and extraordinary stability for over 500 h without noticeable deactivation. The exceptional performance is attributed to the synergistic effect of distinctive Pt1-Ptn structures, which couple the benefits of Pt single atoms and subnanometric clusters in a remarkable way. The disadvantages of single Pt species catalysts, such as sensibility to strong adsorption of CO or reduced lattice oxygen reactivity due to excessive coordination, can be well mitigated. The results of detailed characterizations and density functional theory calculations confirm that the unique structures possess moderate adsorption strength for CO and create abundant active interfacial oxygen species, because of the absence of bulk metallic Pt0 and appropriate coordination to lattice oxygen, which synergistically facilitate the catalytic performance.

Reducing the poisoning effect of adsorbed alkaline earth metal on Nb active sites with sulfates for NH3-SCR

Reducing the poisoning effect of alkaline earth metals over catalysts in industrial fields presents a great challenge to selective catalytic reduction (SCR) of NOx with ammonia. Herein, we successfully introduce sulfates to the surface of supported manganese-based oxides (Nb/MnO2-S) for trapping calcium species, and Nb/MnO2-S catalyst with superior low-temperature performance and calcium-resistant property still exhibits excellent de-NOx activity in a wide operating temperature window (175–350 °C, over 80 % NOx conversion with a gas hourly space velocity of 60,000 h−1) after calcium poisoning. In this case, the addition of sulfates increased the quantity of chemisorbed oxygen on Nb/MnO2-S, thus accelerating the redox cycle in NH3-SCR reaction. Significantly, compared with calcium-poisoned Nb/MnO2, relevant spectroscopy analysis and theoretical calculations further reveal that sulfates species prefer to interact with calcium and release the Nb active sites, which maintains the efficient NH3 adsorption and preserves a large amount of Brønsted acid sites over calcium-poisoned Nb/MnO2-S, thus promoting calcium-resistant performance. This work will provide a general strategy to develop calcium-resistant SCR catalysts with low-temperature activity for industrial applications.

Elaborating the improving SO2 resistance mechanism of CeWTi catalysts through framework confined ordered mesoporous structures for low-temperature NH3-SCR reaction

It is still a significant challenge that enhancing SO2 tolerance on the Ce-based catalyst in NH3-SCR reaction at low temperature. In this paper, an ordered mesoporous Ce-W-Ti-E catalyst with a framework confined structure had been constructed. The active components were directly constrained in the ordered mesoporous TiO2 structure, forming the framework confined ordered mesoporous structure. The ordered mesoporous structures in the framework structure provided better specific surface area and abundant active sites for the catalyst. In addition, the confinement effect of the framework structure enhanced the interaction between Ce, W and Ti, thus speeding up the electron transfer efficiency and enhancing the redox capacity of the catalyst. Furthermore, the introduction of W also supplemented a large amount of surface acid sites, which can inhibit the adsorption of SO2 on the catalyst surface, reduce the deposition of sulfate and well protect the active sites from SO2 attack with the help of special confinement effect. Therefore, the framework confined structure Ce-W-Ti-E catalyst in the whole process of SCR showed a wide operating temperature window, better stability and strong sulfur resistance, thus extended the catalyst lifetime in the NH3-SCR process.

Co Single Atoms and CoOx Nanoclusters Anchored on Ce0.75Zr0.25O2 Synergistically Boosts the NO Reduction by CO

AbstractAchieving high NO conversion and N2 selectivity in selective catalytic reduction of NO by CO (CO‐SCR) in a wide operating temperature window, particularly in the presence of high O2 concentration, remains a big challenge. Herein, guided by density functional theory (DFT) calculations, a catalyst is rationally developed with dual active centers consisting of both Co single‐atoms (SAs) and CoOx nanoclusters (NCs) co‐anchored on Ce0.75Zr0.25O2 support (CZO), which show above 99.7% NO conversion and 100% N2 selectivity at 250–400 °C under 5 vol% O2. DFT calculation and experimental results confirm a strong interaction among Co SAs, CoOx NCs, and CZO support. Co SAs enhance CO adsorption and accompany the oxygen vacancies (OVs) formation in CZO, while the CoOx NCs promote both NO conversion to nitrate intermediate and the breakage of the NO bond at OVs, thus synergistically boosting the N2 formation.

Understanding of low- and high-temperature DeNOx efficiency for NH3-SCR via comparison on Cu modified CHA and AFX zeolites

Pursuing simultaneously with excellent low- and high-temperature (wide operation temperature window) NOx reduction efficiency (LT-/HT-NRE) is greatly appealing for the NH3-SCR applications. We herein reveal the determinant of operation temperature window by comparison of Cu-SSZ-13(CHA) and Cu-SSZ-16(AFX) catalysts. And the outstanding HT-NRE performance is obtained over the Cu0.091-SSZ-164.2 (NOx conversion > 95% up to 670 °C), which makes this catalyst has great potential for applications for HT deNOx. The combined experimental (in-situ DRIFTS) and theoretical studies [DFT, ab initio molecular dynamics &ab initio thermodynamics (AIMD/AIT)] shed deeper mechanistic insights: i) the stronger resistance of Cu speciation ([CuOH]+ → CuOx) and lower HT NH3-overoxidation activity caused by the weak thermodynamic stability of the adsorbed NH3 over Cu active site constitute two major factors leading to the superior HT-NRE of Cu0.091-SSZ-164.2; ii) while the limited internal diffusions of [Cu(NH3)2] to generate the key intermediate of [(NH3)2Cu-O2-Cu(NH3)2] causes its slightly lower LT-NRE than that of Cu0.101-SSZ-135.1. Generally, present work clarifies the NRE performance of Cu-SSZ-16 at both LT and HT, which would progress highly-efficient catalyst development.

In situ cross-linked fluorinated gel polymer electrolyte based on PEGDA-enabled lithium-ion batteries with a wide temperature operating range

Lithium-ion batteries (LIBs) require a wide operating temperature window to meet their actual demand. Herein, a fluorinated gel polymer electrolyte (F-GPE) was synthesised by in situ thermal polymerisation method using poly (ethylene glycol) diacrylate (PEGDA) as a cross-linking agent. The F-GPE showed excellent electrochemical stability in a wide voltage window in the range of 2–5.6 V, high ionic conductivity (above 1.2 mS cm−1 at –40 °C), superior lithium-ion transfer number (tLi+) of 0.51 at room temperature, and good compatibility with lithium metal. Additionally, the LiCoO2||F-GPE||graphite pouch battery, which the surface density of LiCoO2 was 30 mg cm−2, showed an outstanding discharge capacity in a wide temperature from –40 to 60 °C. The results displayed the retention rate of discharge capacities at –40 and 60 °C were 64.9% and 106.3% of that at room temperature, respectively. F-GPE retained the low-temperature performance of the electrolyte and improved the stability and electrochemical behavior at high temperature, providing a new strategy for the large-scale application of LIBs in a wide operating temperature.

Design and identify the confinement effect of active site position on catalytic performance for selective catalytic reduction of NO with NH3 at low temperature

In heterogeneous catalysis, the migration and aggregation of active nanoparticles has always been a challenging problem in catalyst design. Two types of confined catalysts, including the pore confined Pore-CeW/OMT and framework confined FW-CeW/OMT were successfully designed for NH3-SCR process in this work. Experimental results revealed that the framework confined structure could effectively prevent the migration and aggregation of highly dispersed nanoparticles on catalyst. Benefiting from the structural advantages of ordered mesopores TiO2 (OMT), large specific surface area as well as abundant active sites could be supplied for catalytic reaction. It should be noted that citric acid pretreatment was essential for confined catalyst activation. The activation treatment could dramatically enhance catalyst surface acidity, especially a large number of strong acid sites were supplemented, resulting in significantly enhancement of catalytic activity at high temperature. Furthermore, it could also accelerate reduction of Ce4+ to Ce3+ and generate more active oxygen species, which resulted in a significant improvement in its low-temperature catalytic activity. Owning with strong surface acidity as well as framework confinement effect, the unique ordered mesoporous TiO2 framework could inhibit SO2 adsorption and protect active sites from SO2 attacking. Thus, the framework confined FW-CeW/OMT exhibited wide operating temperature window, good thermal stability, as well as strong sulfur resistance in NH3-SCR process.

Sustainable zinc-air battery chemistry: advances, challenges and prospects.

Sustainable zinc-air batteries (ZABs) are considered promising energy storage devices owing to their inherent safety, high energy density, wide operating temperature window, environmental friendliness, etc., showing great prospect for future large-scale applications. Thus, tremendous efforts have been devoted to addressing the critical challenges associated with sustainable ZABs, aiming to significantly improve their energy efficiency and prolong their operation lifespan. The growing interest in sustainable ZABs requires in-depth research on oxygen electrocatalysts, electrolytes, and Zn anodes, which have not been systematically reviewed to date. In this review, the fundamentals of ZABs, oxygen electrocatalysts for air cathodes, physicochemical properties of ZAB electrolytes, and issues and strategies for the stabilization of Zn anodes are systematically summarized from the perspective of fundamental characteristics and design principles. Meanwhile, significant advances in the in situ/operando characterization of ZABs are highlighted to provide insights into the reaction mechanism and dynamic evolution of the electrolyte|electrode interface. Finally, several critical thoughts and perspectives are provided regarding the challenges and opportunities for sustainable ZABs. Therefore, this review provides a thorough understanding of the advanced sustainable ZAB chemistry, hoping that this timely and comprehensive review can shed light on the upcoming research horizons of this prosperous area.

Boosting the catalytic performance of Fe/Zr catalyst by tungsten addition for selective catalytic reduction of NOx with ammonia

To clarify the effect of WO3 doping over Fe/Zr catalyst, several Fe/Zr-xW catalysts were prepared via conventional wet impregnation method, and the selective catalytic reduction (SCR) performance was studied. The Fe/Zr-0.1 W catalyst showed the highest catalytic activity and achieved nearly 100 % in a wide operating temperature window of 300–500 °C, and the N2 selectivity exceeded 90 % over the entire temperature range under a high hour space velocity of 90, 000 h−1. In addition, Fe/Zr-0.1 W catalyst also exhibited superior resistance to SO2 compared to Fe/Zr catalyst without WO3 introduction. Further characterization results indicated that the Fe/Zr-0.1 W catalyst possessed larger BET specific surface area, better dispersion of active component, higher concentration of Fe3+ and more surface chemisorbed oxygen species, which might be the predominant factors for its superior catalytic performance. More importantly, WO3 doping improved the redox capacity and surface acidity, thus promoting the redox circle and enhancing the adsorption ability of NH3. According to the transient in-situ DRIFTS experiment results, the doping of WO3 increased the L-H reaction pathway on the surface of Fe/Zr catalyst during the NH3-SCR reaction. The present work could provide a new way for developing a high-performance non-vanadium SCR catalyst in practical application.

Abundant Oxygen Vacancies Induced by the Mechanochemical Process Boost the Low-Temperature Catalytic Performance of MnO2 in NH3-SCR

Manganese oxides (MnOx) have attracted particular attention in the selective catalytic reduction of NOx with NH3 (NH3-SCR) because of their excellent low-temperature activity. Herein, we prepared a highly efficient MnO2 (MnO2-M) catalyst through a facile ball milling-assisted redox strategy. MnO2-M shows a 90% NOx conversion in a wide operating temperature window of 75–200 °C under a gas hourly space velocity of 40,000 h−1, which is much more active than the MnO2 catalyst prepared by the redox method without the ball-milling process. Moreover, MnO2-M exhibits better H2O and SO2 resistance. The enhanced catalytic properties of MnO2-M originated from the high surface area, abundant oxygen vacancies, more acid sites, and higher Mn4+ content induced by the ball-milling process. In situ DRIFTS studies probed the reaction intermediates, and the SCR reaction was deduced to proceed via the typical Eley–Rideal mechanism. This work provides a facile method to enhance the catalytic performance of Mn-based catalysts for low-temperature denitrification and deep insights into the NH3-SCR reaction process.

Improved Electrochemical Performances of Li/CFx-MnO2 Primary Batteries Via the Optimization of Electrolytes

The lithium(Li) primary batteries have been widely used in power sources for military applications. According to the military standards, the design temperatures for the basic climate category including the mid-altitude areas will include the ambient air temperature range of -32oC through +60oC, considering the operational, storage, and transit conditions of materiel systems. Among a variety of Li primary batteries, lithium/thionyl chloride (Li/SOCl2) primary batteries have been commonly utilized in military applications due to their high energy density, high operating voltage, and competitive cost. However, Li/SOCl2 batteries have serious challenges due to initial voltage delay by lithium chloride passivation layer and possible safety issues by a formation of toxic sulfur-dioxide (SO2) gas and solid sulfur during discharge. To overcome the intrinsic disadvantages of Li/SOCl2 batteries, research into lithium/carbon fluoride-manganese dioxide (Li/CFx-MnO2) batteries has been ramped up for military applications due to their high energy density and good rate capability. In this study, we have focused on an optimization of solvents and Li salts to improve the electrochemical performances of Li/CFx-MnO2 batteries in a wide operating temperature ranges. We have investigated candidate solvents for Li/CFx-MnO2 batteries with different compositions of methyl butyrate (MB) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) as well as conventional solvents including propylene carbonate (PC), 1,2-dimethoxyethane (DME), tetrahydrofuran (THF), ethyl acetate (EA), and 1,2-dioxolane (DOL). Moreover, we have investigated the effects of Li salts, lithium perchlorate (LiClO4) and lithium bis(trifluoromethanesulfonyl)imide (LiFSI), on the electrochemical performances in the low and high operating temperatures. Ionic conductivity measurements and differential scanning calorimetry (DSC) analysis were also carried out to investigate the physical properties and stability of electrolyte. This study will provide an opportunity to develop the new electrolyte systems for Li/CFx-MnO2 batteries in a wide operating temperature window.

Novel manganese-based assembled nanocatalyst with “nitrous oxide filter” for efficient NH3-SCR in wide low-temperature window: Optimization, design and mechanism

It is still a challenge for de-NOx catalysts to have high activity and N2 selectivity in a wide low-temperature operating temperature window. In this work, we used layered zeolite-like montmorillonite as the support and then obtained a composite catalyst with satisfactory NOx conversion and excellent N2 selectivity in the temperature range of 100–300 °C with the method of pillaring modification, active component doping, and catalyst assembly. It has been proved that doping rare earth elements can improve the redox ability of the catalyst, and WO3 modification can enhance the acidity of the catalyst. The redox ability and the surface acidity of the catalyst system were balanced by assembling the WO3-modified catalyst and the WO3-unmodified catalyst. Besides, we found the composite Pr1Mn9/Fe7Ti3-Wu-mmt catalyst had the best catalytic activity and N2 selectivity only when the reaction gas first passed through the catalyst modified by WO3, in which the WO3-modified catalyst acted as the role of nitrous oxide filter. What’s more, according to the results of in situ DRIFTS, it can be indicated that the montmorillonite-supported catalysts in this work followed the L-H mechanism and E-R mechanism; while the E-R mechanism was dominant when the catalyst was modified by WO3. The results in present work indicate that the novel strategy of assembling catalysts is practicable to obtain an efficient de-NOx catalyst with a wide low-temperature operating temperature window, high NOx conversion, and high N2 selectivity. Furthermore, the novel assembly strategy of tandem catalysis with stronger acidity sites and redox sites in turn “acidityu & redoxd” can be extended to other SCR catalytic systems.

Bimetallic modification of MnFeOx nanobelts with Nb and Nd for enhanced low-temperature de-NOx performance and SO2 tolerance

Nitrogen oxide (NOx) is one of the key factors contributing to air pollution, and selective catalytic reduction with ammonia (NH3-SCR) is widely used for denitrification (de-NOx). To effectively deal with the NOx pollution, it is urgent to develop efficient catalyst working at below 300 °C with a wide operating temperature window. Herein, a series of ferromanganese oxides (MnFeOx) nanobelts are bimetallically modified with niobium (Nb) and neodymium (Nd) for the first time via electrospinning method. The resultant MnFeNbNdOx catalysts present improved low-temperature de-NOx performance and sulfur dioxide (SO2) tolerance, particularly MnFeNb0.2Nd0.1Ox who achieves a NOx conversion up to over 90 % during the range of 120–330 °C and an enhanced tolerance of water (H2O) and SO2. Experimental and theoretical calculations confirm that strong adsorption of nitric oxide (NO) and ammonia (NH3) and weak adsorption of SO2 with the synergy of Nd, Nb and Mn enable MnFeNb0.2Nd0.1Ox excellent SCR activity and good SO2 tolerance. In-situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) further reveal that the de-NOx reaction over MnFeNb0.2Nd0.1Ox follows both Eley-Rideal (E-R) and Langmuir-Hinshel-wood (L-H) mechanisms. This study will inspire the further design and study of the synergy of transition metals and rare earth elements for de-NOx.

Single-Atom Ce-Modified α-Fe2O3 for Selective Catalytic Reduction of NO with NH3.

A single-atom Ce-modified α-Fe2O3 catalyst (Fe0.93Ce0.07Ox catalyst with 7% atomic percentage of Ce) was synthesized by a citric acid-assisted sol-gel method, which exhibited excellent performance for selective catalytic reduction of NOx with NH3 (NH3-SCR) over a wide operating temperature window. Remarkably, it maintained ∼93% NO conversion efficiency for 168 h in the presence of 200 ppm SO2 and 5 vol % H2O at 250 °C. The structural characterizations suggested that the introduction of Ce leads to the generation of local Fe-O-Ce sites in the FeOx matrix. Furthermore, it is critical to maintain the atomic dispersion of the Ce species to maximize the amounts of Fe-O-Ce sites in the Ce-doped FeOx catalyst. The formation of CeO2 nanoparticles due to a high doping amount of Ce species leads to a decline in catalytic performance, indicating a size-dependent catalytic behavior. Density functional theory (DFT) calculation results indicate that the formation of oxygen vacancies in the Fe-O-Ce sites is more favorable than that in the Fe-O-Fe sites in the Ce-free α-Fe2O3 catalyst. The Fe-O-Ce sites can promote the oxidation of NO to NO2 on the Fe0.93Ce0.07Ox catalyst and further facilitate the reduction of NOx by NH3. In addition, the decomposition of NH4HSO4 can occur at lower temperatures on the Fe0.93Ce0.07Ox catalyst containing atomically dispersed Ce species than on the α-Fe2O3 reference catalyst, resulting in the good SO2/H2O resistance ability in the NH3-SCR reaction.

Transformation of Thermal Expansion from Large Volume Contraction to Nonlinear Strong Negative Thermal Expansion in PbTiO3-Bi(Co1-xFex)O3 Perovskites.

Controlling negative thermal expansion (NTE) is an important topic in the study of NTE materials. Generally, a large magnitude of NTE with a wide NTE operation temperature window is preferable for applications of NTE materials, as a stronger NTE can be used to tailor the coefficient of thermal expansion (CTE) of materials with positive thermal expansion by forming composites more efficiently. However, controlling the NTE in single-phase materials is still a significant challenge. In present study, we proposed a promising method to control the thermal expansion from large volume contraction in a limited temperature widow (x = 0, ΔV = -4.8%, 675-700 °C) to a nonlinear strong NTE over a wider temperature range (x = 0.8, α̅V = -6.12 × 10-5/°C, RT to 600 °C) by means of adjusting the proportion of cations with different ferroelectric activities in 0.5PbTiO3-0.5Bi(Co1-xFex)O3 ferroelectrics. The obtained NTE was stronger than many of the currently available NTE materials, and the operation window of NTE was also in an extended temperature range. The unusual transformation is well explained by the spontaneous volume ferroelectrostriction effect, which was evidenced by joint experimental and theoretical studies. The present work not only may pave the way for controllable large NTE in PbTiO3-based ferroelectrics but also could be extended to magnetic NTE materials, whose NTE is coupled with magnetism.

A Bifunctional Multishell Catalyst with a Wide Operating Temperature Window for NOx Abatement by Ammonia-Selective Catalytic Reduction

A Bifunctional Multishell Catalyst with a Wide Operating Temperature Window for NO_<i>x</i> Abatement by Ammonia-Selective Catalytic Reduction

Closo-Borate Gel Polymer Electrolyte with Remarkable Electrochemical Stability and a Wide Operating Temperature Window.

A major challenge in the pursuit of higher‐energy‐density lithium batteries for carbon‐neutral‐mobility is electrolyte compatibility with a lithium metal electrode. This study demonstrates the robust and stable nature of a closo‐borate based gel polymer electrolyte (GPE), which enables outstanding electrochemical stability and capacity retention upon extensive cycling. The GPE developed herein has an ionic conductivity of 7.3 × 10−4 S cm−2 at room temperature and stability over a wide temperature range from −35 to 80 °C with a high lithium transference number (tLi+ = 0.51). Multinuclear nuclear magnetic resonance and Fourier transform infrared are used to understand the solvation environment and interaction between the GPE components. Density functional theory calculations are leveraged to gain additional insight into the coordination environment and support spectroscopic interpretations. The GPE is also established to be a suitable electrolyte for extended cycling with four different active electrode materials when paired with a lithium metal electrode. The GPE can also be incorporated into a flexible battery that is capable of being cut and still functional. The incorporation of a closo‐borate into a gel polymer matrix represents a new direction for enhancing the electrochemical and physical properties of this class of materials.