Reduced Operating Temperature Research Articles

Enriching Nano-Heterointerfaces in Proton Conducting TiO2-SrTiO3@TiO2 Yolk-Shell Electrolyte for Low-Temperature Solid Oxide Fuel Cells.

A challenging task in solid oxide fuel cells (SOFCs) is seeking for an alternative electrolyte, enabling high ionic conduction at relatively low operating temperatures, i.e., 300-600°C. Proton-conducting candidates, in particular, hold a significant promise due to their low transport activation energy to deliver protons. Here, a unique hierarchical TiO2-SrTiO3@TiO2 structure is developed inside an intercalated TiO2-SrTiO3 core as "yolk" decorating densely packed flake TiO2 as shell, creating plentiful nano-heterointerfaces with a continuous TiO2 and SrTiO3 "in-house" interfaces, as well the interfaces between TiO2-SrTiO3 yolk and TiO2 shell. It exhibits a reduced activation energy, down to 0.225eV, and an unexpectedly high proton conductivity at low temperature, e.g., 0.084 S cm-1 at 550°C, confirmed by experimentally H/D isotope method and proton-filtrating membrane measurement. Raman mapping technique identifies the presence of hydrogenated HO─Sr bonds, providing further evidence for proton conduction. And its interfacial conduction is comparatively analyzed with a directly-mixing TiO2-SrTiO3 composite electrolyte. Consequently, a single fuel cell based on the TiO2-SrTiO3@TiO2 heterogeneous electrolyte delivers a good peak power density of 799.7mW cm-2 at 550°C. These findings highlight a dexterous nano-heterointerface design strategy of highly proton-conductive electrolytes at reduced operating temperatures for SOFC technology.

Structure-dependent biomorphology Co3O4-In2O3 nanorods for expired acetone gas sensor

Currently, the detection of acetone in exhaled breath is extensively utilized for the preliminary diagnosis of diabetes and for tracking fat oxidation in exercise. However, semiconductor gas sensors often require enhancement in breath analysis because of their inherent limitations in selectivity and sensitivity to humidity. In this research, we have synthesized an effective and humidity-unaffected acetone sensing material. This was achieved by utilizing the surface induction effect of porous biomass carbon derived from hemp stems to promote the dispersion of Co3O4-In2O3 heterostructure composites, thereby increasing the availability of active sites. This unique structure is achieved by precisely integrating the p-n heterostructure formed by Co3O4-In2O3 nanorods with the hierarchical porous carbon skeleton obtained via the calcination of templates. The p-n heterostructure enhances charge carrier concentration at the interface, thereby augmenting the activation of surface-active oxygen. The composite material's interface barrier improves sensor selectivity, reducing operating temperature (200 °C) and enhancing response rate. In this work, our best sample Coln-3/BC gas sensor exhibits excellent response towards acetone gas (S=Rair/Rgas=56.8 at 100 ppm), low detection limit of 10 ppb, a linear relationship between sensing response and humidity that strikes a balance between irrelevance as well as exceptional selectivity and stability. Therefore, constructing hierarchical structures and gas-sensing materials based on p-n heterojunctions holds promising prospects.

Innovative Closed Cavity Façades (CCF) with Inner Shading and Advanced Coatings for Enhancing Thermal Performance in the Tropics

In its simplest terms, a closed-cavity façade (CCF) is a sealed, unventilated enclosure equipped with motorized shading devices, internal double or triple glazing, and external single glazing. This technology effectively controls solar energy and daylight entry into buildings. This research aims to enhance the thermal efficiency of CCFs in tropical climates using Venetian blinds (VB) and advanced glass coatings. EnergyPlus and DesignBuilder were employed to assess various CCF designs and compare them to a single glazing unit (SGU) with grey coatings. This was inspired by a residential case study on Penang Island, Malaysia. The findings indicate that CCFs surpass SGUs in thermal performance and occupant comfort, particularly in Malaysia’s humid tropical climate. CCFs reduced operating temperatures by a monthly percentage ranging from 33.5% to 68.75% in all operations. On an annual basis, temperature reductions ranged from 27.5% to 80.25%, with maximum decreases between 2 °C and 4 °C and minimum decreases between 0.5 °C and 1 °C compared to SGU units. The results show that CCFs outperform SGUs in thermal performance and comfort, reducing operating temperatures by 33.5% to 68.75% monthly and 27.5% to 80.25% annually. Temperature reductions ranged between 2 °C and 4 °C at maximum and 0.5 °C and 1 °C at minimum compared to SGU. Notably, Venetian blinds with nano-coatings (83/58) and low-E coatings (83/23) (Tvis/Tsol) were the most effective. This study highlights the importance of selecting appropriate coatings for CCFs, and demonstrates their potential in enhancing interior temperatures and comfort in Malaysia’s climate. The findings emphasize the significant impact of innovative glazing technologies on improving operational temperatures and occupant comfort using closed-cavity façades in the tropics.

A bio-inspired shape memory alloy-based smart fin system for adaptive thermal management

Thermal management systems utilizing fixed-area extended surfaces for thermal enhancement have been extensively investigated. Unlike these systems, in nature, few creatures display the ability to control heat dissipation in adaptation to changes in environmental conditions by controlling their exposed surface area of the body. Motivated by this, the primary objective of this research is the design, development, numerical and experimental evaluation of an adaptive variable area smart fin system for intelligent thermal management using a high-strain SMA spring actuator. Unlike most thermal management devices and techniques that involve a fixed surface area, a smart fin controlled by Pennate structure-based SMA (PeSMA) actuator is proposed for large actuation and compact arrangement. The capabilities of the smart fin to adaptively enhance heat transfer are experimentally demonstrated and numerically modeled. The proposed fin design can deliver improved thermal performance in terms of reduced operating temperature and pressure drop, which is an indicator of operational cost when the application involves variable and uncertain thermal load conditions. We envisage one of the future applications of this technology in the battery thermal management of Electric Vehicles (EVs) where deployable compact heat transfer system is highly desirable.

From Double Skin Facade to Closed Cavity Façade with Triple Glazed Unite as Inner Skin Without Coatings in the Tropical Climate of Malaysia

The Close Cavity Façade (CCF) has undergone significant advancements from its predecessor, the Double Skin Façade (DSF), resulting in improved thermal insulation and reduced solar penetration. The core principle behind a CCF is a hermetically sealed and non-ventilated construction that incorporates an automatic shading system, triple glazing (TGU) on the inner surface, and single glass on the outer surface. The technique described above effectively regulates the ingress of solar energy and natural light into the building. The experimentation involved the utilisation of various combinations of CCF-TGU designs, employing software tools such as Window 7.8, EnergyPlus, and DesignBuilder. Then, a comparison analysis was undertaken to compare the aforementioned designs with the presently employed single-glazed units (SGU) featuring a grey coating. The inquiry was initiated through the implementation of a case study carried out on a condominium located on Penang Island, Malaysia. The CCF-TGU has superior thermal performance and provides enhanced occupant comfort when compared to SGUs. The effectiveness of CCF-TGU designs in reducing operating temperature ratios has been observed to be higher in Malaysia's humid tropical climate than that of SGUs. The annual rate of decrease varies between 29.8% and 77.8%, thereby successfully attaining the required level of thermal comfort. The research highlights the potential advantages of implementing an innovative CCF technology that has been modified to accommodate the distinct meteorological conditions of Malaysia. The findings suggest that the implementation of advanced glazing technology holds the potential to enhance both operational temperatures and overall occupant comfort within buildings.

(Invited) Development of Thin-Film Solid Oxide Cells for Power Generation and Hydrogen Production

Thin-film solid oxide cells (TF-SOCs) fabricated by sputtering have been developed for power generation and hydrogen production applications. TF-SOCs have been considered for cell configuration in this development because of the potential for efficient operation at reduced temperatures (≤700oC). Reduced temperature operation allows a wider choice of cell and ancillary materials, minimizes elemental migration/interaction, and reduces thermal stresses, thus improving cell reliability and durability. Sputtering has been considered for fabrication of TF-SOCs because the technique can create dense or porous films as required for the cell components. In addition, a fabrication process based on sputtering is readily scaled to large cell sizes and large volume production. All-sputtered TF-SOC cells have been shown to exhibit exceptionally high performance in both power generation and electrolysis modes, for example, a peak power density of 2.7W/cm2 (fuel cell mode) and a current density of 2.6A/cm2 at 1.3V (electrolysis mode) at 650oC with 50%H2-50%H2O. TF-SOC cells as large as 15 cm x 15 cm size have been fabricated by sputtering. This paper discusses the development of the sputtering process for making TF-SOCs and evaluation of cell performance characteristics in power generation and hydrogen production operating modes.

(Invited) Materials Stability in Anode-Supported Solid Oxide Cells

Professor Anil Virkar has been a pioneer in the development and characterization of high-performance anode-supported solid oxide fuel cells, and in understanding degradation processes in such cells operated in electrolysis mode. This talk reviews methods for improving anode-supported cells, particularly for yielding high performance at reduced operating temperature. The understanding of degradation mechanisms occurring during solid oxide electrolysis cell operation will be discussed.

A Study on Electrochemical Properties of Fuel-Electrode-Supported Reversible Solid Oxide Cells

Introduction Reversible solid oxide cells (r-SOCs) enable both power generation and steam electrolysis, and have attracted attention as a solid state electrochemical energy device for a decarbonized society (1). R-SOCs have the advantage of high efficiency due to high temperature operation, but there exist various technical issues remained in materials selection, start-up and shutdown, and long-term durability. Therefore, reducing operating temperature is desirable for practical applications (2,3). Electrode-supported cells, in which the electrode acts as a structural support, enable lower temperature operation by reducing the thickness of the electrolyte, which has certain electrical resistivity. Here in this study, the current-voltage characteristics and reversible cycle durability under r-SOC operating conditions are evaluated using fuel-electrode-supported cells, with the aim of developing r-SOCs capable of highly efficient fuel cell power generation and steam electrolysis. Experimental For the experiments, fuel-electrode-supported cells were fabricated using fuel electrode-supported half-cells (Japan Fine Ceramics, Japan), schematically shown in Fig. 1. The half-cell consists of scandia-stabilized zirconia (ScSZ: 10 mol%Sc2O3-1mol%CeO2-89 mol%ZrO2) or yttria-stabilized zirconia (YSZ: 8 mol%Y2O3-92 mol%ZrO2) electrolyte and a Ni-cermet fuel electrode, such as Ni-ScSZ or Ni-YSZ. (La0.6Sr0.4)(Co0.2Fe0.8)O3 (LSCF) was applied for the air electrode, and Gd0.1Ce0.9O2 (GDC) was inserted between the electrolyte and the air electrode to suppress interdiffusion and chemical reactions. Four types of cells were used with different combinations of the electrolyte component (YSZ or ScSZ) in the electrolyte layer or the supporting fuel electrode.In electrochemical tests, 50%-humidified hydrogen (100 ml min-1) was supplied to the fuel electrode, and air (150 ml min-1) was supplied to the air electrode. R-SOC initial performance tests were conducted using an electrochemical analyzer (1255B, Solartron). Cell voltage and impedance were measured at 700-800°C at current densities ranging from -0.5 A cm-2 to +0.5 A cm-2. Positive current density means the value in SOFC mode, while negative current density means the value in SOEC mode. In r-SOC 1,000 cycle durability tests, cycles of switching between SOFC and SOEC operation were repeated 1,000 times by varying current density. The range of current density in the cycle tests was between -0.2 A cm-2 and +0.2 A cm-2. The cell impedance was measured before the cycling test and every 100 cycles. After each test, the cells were analyzed by using a focused-ion beam scanning electron microscopy (FIB-SEM) to observe and evaluate the electrode microstructure. Results and discussion Figure 2 (a) shows the r-SOC initial performance of each fuel-electrode-supported cell. The cell with the Ni-YSZ fuel electrode and the YSZ electrolyte showed better current voltage characteristics than other cells. Figure 2 (b) shows the r-SOC 1000-cycle durability of the cell with the Ni-YSZ fuel electrode and the YSZ electrolyte. The results showed a decrease in power generation and electrolysis performance with increasing the number of cycles in both SOFC and SOEC modes. Possible degradation mechanisms will be discussed. Acknowledgments This paper is based on results obtained from a project (Research and Development Program for Promoting Innovative Clean Energy Technologies Through International Collaboration), JPNP20005, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Collaborative support by Prof. H. L. Tuller and Prof. B. Yildiz at Massachusetts Institute of Technology (MIT) is gratefully acknowledged. References (1) Venkataraman, M. Pérez-Fortes, L. Wang, Y. S. Hajimolana, C. Boigues-Muñoz, A. Agostini, S. J. Mcphail, F. Mar échal, J. V. Herle, and P. V. Aravind, J. Energy Storage, 24, 100782 (2019).(2) Subotić, S. Pofahl, V. Lawlor, N. H. Menzler, T. Thaller, and C. Hochenauer, Energy Proc., 158, 2329 (2019).(3) B. Mogensen, Current Opinion Electrochem., 21, 265 (2020). Figure 1

Enhanced stability and electrochemical investigations of Ni/ZSM-5 catalyst layer on nickel-based anodes for ammonia-fed solid oxide fuel cells

Ammonia-fed solid oxide fuel cell (SOFC) is a promising clean energy technique with distinctive advantages of zero-carbon emission, easy storage, and high efficiency. However, the typical nickel anode for SOFC is susceptible to structural change and performance degradation under an ammonia environment, particularly at reduced operating temperatures. In addition, obtaining a deep understanding of the individual electrode processes is demanded for the rational design and optimization of NH3–SOFCs. This work enhances the cell performance and durability of ammonia-fed SOFCs by utilizing a cost-effective ammonia decomposition catalyst (Ni/Na-ZSM). The electrode processes are investigated quantitively using distributed relaxation time (DRT) and equivalent circuit model (ECM) analysis. Accelerated degradation tests are conducted for the NH3-based SOFC cells by thermal cycling at operational temperatures of 700 °C-650 °C. Compared to the conventional cell, the cell with the Ni/Na-ZSM catalyst exhibits improved cell performance and five times less decay. In situ measurements and impedance analysis combined with microstructural characterization reveal that the durability enhancement is probably ascribed to protecting the structure of the three-phase boundaries (TPBs), which maintains a stable resistance of the TPB charge transfer processes during the temperature cycling.

Fuel-Flexible Ceramic Fuel Cells at Reduced Operating Temperatures

Ceramic fuel cells are uniquely capable of generating power using a wide range of fuels, including hydrogen, hydrocarbons, and ammonia. One of the primary issues of ceramic fuel cells for large-scale power generation originates from the high operating temperature, which leads to limited material choices for interconnects and sealants, expensive balance of plants, slow start-up and shutdown cycles, and high degradation rates, inevitably limiting their scaleup and commercialization. Reducing the temperature to <600 °C could transform the architecture and operation of ceramic fuel cells. However, the internal reforming of hydrocarbons is endothermic, which is thermodynamically and kinetically unfavorable at lowered operating temperatures, necessitating the development of internal reforming catalysts to enhance the anode catalytic activity. This talk will first focus on presenting the approaches that have been validated for designing and synthesizing internal reforming catalysts, with a particular focus on internal steam reforming and dry reforming of methane. Additionally, the characterization of high-performance ceramic fuel cells equipped with these catalysts will also be discussed. The associated challenges and proposing strategies from different perspectives will also be provided in this talk.

Layered Monoclinic Perrierite Oxo-Silicate La4Mn5Si4O22+Δ: A New Interstitial Oxide Ion Conductor for Low Temperature Applications

Oxide-ion conductors are important for various energy applications such as solid oxide fuel cells, solid oxide electrolyser cells, oxygen separation membranes, oxygen sensors, etc. State-of-the-art stable oxygen active materials often have adequate oxygen ion diffusion and chemical surface exchange only at high temperatures (> 700 oC). A promising strategy to improve the oxygen ion transport is to use the interstitial oxygen ion conductors as the interstitial diffusion barriers are often lower than vacancy-mediated diffusion barrier, potentially enabling reduced operation temperatures. However, due to the large size of the oxide ion, the formation of an adequate concentration of interstitials is difficult and hence the number of interstitial oxygen conductors is currently limited to just a handful of compounds, e.g., Ruddlesden-Popper, apatite, melilite, scheelite, fluorite and disordered hexagonal perovskites.We screened a large number of oxide materials using high-throughput ab initio methods (Please see separate poster from Jun Meng on this screening) and predicted stable formation and fast diffusion of interstitial oxygen in a new class of material La4Mn5Si4O22+δ (LMS), motivating us to synthesize this material and experimentally study its oxide ion transport properties. The room temperature X-ray diffraction study followed by Rietveld refinement confirmed its layered monoclinic perrierite structure. Electron probe micro-analysis (EPMA) and iodometric titration revealed the presence of the hyper stoichiometric oxygen anion (δ ~ + 0.5) confirming the interstitial oxygen ions within LMS lattice. Thermogravimetric analysis showed a small mass increment in LMS when heated at high temperatures suggesting the high temperature stability of interstitial oxygen ions. The measured ionic conductivity of LMS is higher than the yttria stabilized ZrO2, perovskite oxide La1-xSrxCo1-yFeyO3 and Ruddlesden-Popper oxide materials. Electrical conductivity relaxation studies demonstrated that self-diffusion and surface exchange coefficients of oxygen ion are comparable to or higher than many state-of-the-art oxide ion conductors. Finally, the high temperature stability of the synthesised material was confirmed using X-ray diffraction after each measurement.Overall, this experimental study confirms computational predictions that layered perrierite LMS is a new class of interstitial oxide ion conductors and suggests our overall approach may help the rational design of interstitial mediated oxide ion conductors-based devices suitable for efficient and stable applications at low temperature.

Potential for supply temperature reduction of existing district heating substations

Reducing operating temperatures is a crucial goal for transforming district heating networks into sustainable systems as it allows the integration of low exergy heat (e.g. renewable, waste heat). Many criticalities arise when reducing operating temperatures in existing networks that are not designed to operate in these conditions. The criticalities occur at different levels: in the building, in the thermal substations, in the pipelines and in the production plants. In this paper, the reduction of supply temperature in existing district heating substations is analyzed. A methodology including a model of the thermal substation and a data analysis software is developed to estimate the potential temperature reduction that could be applied to existing substations. The application of the model to an existing large-scale district heating network in Northern Italy shows that all the analyzed substations are currently able to shift their operation from 120 °C to 104 °C, and that district heating supply temperatures around 90 °C can be realistically achieved with few improvements on the system.

Overview of Approaches to Increase the Electrochemical Activity of Conventional Perovskite Air Electrodes.

The progressive research trends in the development of low-cost, commercially competitive solid oxide fuel cells with reduced operating temperatures are closely linked to the search for new functional materials as well as technologies to improve the properties of established materials traditionally used in high-temperature devices. Significant efforts are being made to improve air electrodes, which significantly contribute to the degradation of cell performance due to low oxygen reduction reaction kinetics at reduced temperatures. The present review summarizes the basic information on the methods to improve the electrochemical performance of conventional air electrodes with perovskite structure, such as lanthanum strontium manganite (LSM) and lanthanum strontium cobaltite ferrite (LSCF), to make them suitable for application in second generation electrochemical cells operating at medium and low temperatures. In addition, the information presented in this review may serve as a background for further implementation of developed electrode modification technologies involving novel, recently investigated electrode materials.

Passive thermal management strategy for cooling multiple portable electronic components: Hybrid nanoparticles enhanced phase change materials as an innovative solution

Modern electronics technologies have given great interest to phase change materials (PCMs). The present work is in line with this philosophy and deals with the effectiveness of a PCM-based heat sink and nanoparticles in insertion for thermal management of several electronic components. Present numerical study explores the solid-liquid phase change process of n-eicosane in an enclosure considered for cooling of electronics in the presence of one, two, and three protruding electronic components. To improve thermal management capability, four types of nanoparticles, namely, silver (Ag), magnesium oxide (MgO), multi-walled carbon nanotube (MWCNT), and silicon dioxide (SiO2), are inserted into the n-eicosane by single and hybrid ways at volume fractions ranging from 0 % to 4%, and by introducing a lateral fin playing the role of a motherboard. It should be noted that this study is interested in analysing the combined effects of the volume fraction of inserted nanoparticles ranging from 0 % to 4%, the type of inserted nanoparticles, and the number of electronic components installed at the heat sink on the overall heat transfer and flow structure of the fluid PCM. For this purpose, a mathematical model has been developed for the formulation of the governing equations of the conjugate natural convection. The enthalpy-porosity technique is applied for modelling the phase change process. Results reveal a significant relationship between the melting time and the operating temperature of the electronic component. A long phase change process is characterized by a high utilization of latent heat and subsequently the heat rejection becomes efficient. Hence, the longer melting times result in reduced operating temperatures. By insertion of SiO2-MWCNT hybrid nanoparticles, the melting time is increased by approximately 92 % compared to pure PCM, and the plateau temperature is mitigated by 11 °C by using one component in the enclosure. Furthermore, by increasing the number of electronic components, the flow structure, thermal field and melting front become more uniform. Thus, it can be recommended to use three electronic components with a lower heat generation rate instead of using one electronic component with three times higher heat dissipation in a PCM-based cooling system.

Electron structure effects of S-doped In2O3 flowers on NO2 sensitivity

To further develop sensing materials for NO2 gas detection practical application, the operating temperature of the sensor should be significantly reduced. In this paper, In2O3 flowers were prepared by the microwave-assisted hydrothermal method. Then, In2O3 was doped using TAA (thioacetamide). The prepared S-doped In2O3 flowers have good gas sensitivity and significantly reduced operating temperature. When exposed to 10 ppm NO2 gas, the corresponding response was 250 at 118 °C. It can be demonstrated by the first principle calculations, in which the doping of S atoms changes the electron structure of In2O3 from semiconductor to metal with a lower potential barrier. Then, significantly affects the electron crossing the intergranular potential barriers. Therefore, the operating temperature of the sensor can be reduced. Our research results will provide new research ideas and technical approaches for designing, fabricating, and applying a new generation of In2O3 gas sensors.

Comparative review and evaluation of state-of-the-art photovoltaic cooling technologies

Photovoltaic systems have a reliable method to generate electrical power from direct solar irradiance. Their efficiency is only up to 20% in real operating circumstances and is affected adversely by the inevitable temperature rise in their surface. Passive, active or combined cooling methods are applied to reduce operating temperature to a suitable level, depending on specific application. A Great body of literature has been investigating different PV cooling methods and techniques to reach optimized system efficiency and cooling effect. It is critical for both researchers and practitioners to have a thorough understanding and awareness of the most recent advances and existing gaps. Although there are certain review papers in this field, it is necessary to have up-to-date reviews of the most recent progress and research since the previous ones. In the present work, the main focus was to provide a review of the most recent studies and to compare their outcomes to provide a reference for practitioners and researchers. The holistic classification and evaluation of all the possible cooling technologies were provided in order to draw a comparison between various cooling approaches. Based on the analysis obtained, cooling techniques can ensure improvement in electrical efficiency in a range from 1% to 53% with expected decrease in the photovoltaic panel's surface operating temperature from 1.8 °C to 46 °C. It was also found that spectrum filtering and jet impingement indicated highly remarkable enhancements. The other factors, such as the size of the examined photovoltaic panel, photovoltaic technology, as well as climate circumstances have a strong impact on the cooling performance besides the selection of the specific coolant. The necessity for integral evaluation (performance, economic and environmental) of cooling techniques was also identified as key issue.

Mn-Ce Oxide Nanoparticles Supported on Nitrogen-Doped Graphene for Low-Temperature Catalytic Reduction of NOx: De-Nitration Characteristics and Kinetics

Selective catalytic reduction (SCR) of NOx with NH3 as the reductant has been proven an efficient and cost-effective technology to remove NOx pollutants in industries. Traditional SCR catalysts usually operate above 300 °C and suffer from intoxication and limited lifetime. Nano-catalysts are attractive for their high catalytic activities at reduced operating temperatures. We have recently developed a series of nitrogen-doped graphene-supported Mn-Ce oxides (MnCeOx/NG). The influences of reaction temperature, space velocity, mole ratio of NH3/NO and O2 concentration on SCR de-nitration activity were assessed. The novel catalyst with optimal Mn/Ce ratio, at appropriate processing conditions, can achieve a NO conversion efficiency of 99.5% at a temperature of 180 °C, and 93.5% at 150 °C. The kinetics of the SCR reaction on this novel catalyst were also established, exhibiting first-order with respect to NO, zero-order to NH3, and nearly 0.5-order to O2 at low temperatures. In the presence of sufficient O2 content, the apparent activation energy of the NH3-SCR on MnCeOx/NG is 37.6 kJ/mol, which is promising for low-temperature applications.

PdAg alloy modified SnO2 nanoparticles for ultrafast detection of hydrogen

Hydrogen is rapidly applied worldwide as a carbon-free energy carrier, while the rapid detection of leaked hydrogen concentration is still a challenging problem. A sensitive material based on PdAg alloy modified SnO2 nanoparticles for rapid detection of hydrogen is successfully prepared. The Pd4Ag/SnO2 based sensor displays ultrafast response rate (1 s @ 1000 ppm), high response value (2843 @ 1000 ppm) and outstanding selectivity to hydrogen. To date, Pd4Ag/SnO2 prepared in this study exhibits the fastest response rate among the bimetal modified semiconductor metal oxide hydrogen sensors reported. Furthermore, PdAg alloy is used to construct a co-sensitizer with low activation energy, further displaying a reduced operating temperature. Detailed sensing mechanism demonstrates that the enhanced hydrogen sensing capability of PdAg/SnO2 is related to the synergistic effect of PdAg alloy, including the catalytic sensitization triggered by Pd and Ag as well as abundant chemisorbed oxygen introduced by PdAg alloy. The PdAg/SnO2 based sensor with superior hydrogen sensing properties provides the possibility for development of a novel rapid response hydrogen sensor.

High-Performance Ppb Level NO2 Gas Sensor Based on Colloidal SnO2 Quantum Wires/Ti3C2Tx MXene Composite.

Nitrogen dioxide is one origin of air pollution from fossil fuels with the potential to cause great harm to human health in low concentrations. Therefore, low-cost, low-power-consumption sensors for low-concentration NO2 detection are essential. Herein, heterojunction by SnO2 quantum wires, a traditional metal oxide NO2 sensing material, and Ti3C2Tx MXene, a novel type of 2D layered material, was synthesized using a simple solvothermal method for enhancing gas-sensing performance and reducing operating temperature. The operating temperature was reduced to 80 °C, with a best performance of 27.8 and a fast response and recovery time (11 s and 23 s, respectively). The SnO2 and Ti3C2Tx MXene composite exhibits high speed and low detection limit due to the construction of the heterojunction with high conductive Ti3C2Tx MXene. The selectivity and stability of gas sensors are carried out. This could enable the realization of fast response, high-sensitivity, and selective NO2 sensing under low operating temperatures.

Nb-doped La0.6Sr0.4FeO3-δ as an electrolyte for intermediate-temperature solid oxide fuel cells.

It is one of the effective strategies to develop intermediate-temperature solid oxide fuel cells (IT-SOFCs) by looking for alternative electrolyte materials that can maintain or even improve current cell efficiencies while reducing operating temperature. In this study, by rationally introducing pentavalent Nb on the B-site of La0.6Sr0.4FeO3-δ (LSFO), a serial of novel perovskite La0.6Sr0.4Fe1-xNbxO3-δ (LSFNbx, x = 0.1, 0.2) with mixed electron-ion conduction is successfully prepared. The electrochemical mechanism and performance of the symmetrical IT-SOFCs with a single LSFNbx perovskite oxide as electrolyte are investigated. With the Nb doping, the structure stability of the LSFO is improved and the electronic conductivity decreases. La0.6Sr0.4Fe0.8Nb0.2O3-δ (LSFNb20) is the most promising electrolyte of the three candidates as it has the best performance (735 mW cm-2 at 550 °C in a dry H2/Air atmosphere) and no short-circuiting problem. The applied voltage-response current curves demonstrate that the interface between the Ni-Ni0.8Co0.15Al0.05LiO2-δ anode and LSFNb20 electrolyte can block electron conduction more efficiently and has a better promoting effect on protons, which is fundamentally due to the band energy alignment of the interface heterojunction. Our work highlights that LSFNb20 is a high-performance perovskite alternative to monolayer electrolytes.