Oxide Research Articles

Emerging Biohybrids of Aptamer-Based Nano-Biosensing Technologies for Effective Early Cancer Detection.

Cancer is a leading global cause of mortality, which underscores the imperative of early detection for improved patient outcomes. Biorecognition molecules, especially aptamers, have emerged as highly effective tools for early and accurate cancer cell identification. Aptamers, with superior versatility in synthesis and modification, offer enhanced binding specificity and stability compared with conventional antibodies. Hence, this article reviews diagnostic strategies employing aptamer-based biohybrid nano-biosensing technologies, focusing on their utility in detecting cancer biomarkers and abnormal cells. Recent developments include the synthesis of nano-aptamers using diverse nanomaterials, such as metallic nanoparticles, metal oxide nanoparticles, carbon-derived substances, and biohybrid nanostructures. The integration of these nanomaterials with aptamers significantly enhances sensitivity and specificity, promising innovative and efficient approaches for cancer diagnosis. This convergence of nanotechnology with aptamer research holds the potential to revolutionize cancer treatment through rapid, accurate, and non-invasive diagnostic methods.

Multi-objective topology optimization design of silicon carbide metal oxide semiconductor field effect transistors power module liquid-cooled heatsink for electric vehicles

Silicon carbide (SiC) metal oxide semiconductor field effect transistors (MOSFETs) is gradually replacing silicon-based insulated gate bipolar transistor (IGBT) as the switching devices in electric vehicle power inverters due to its higher operating temperatures, switching speeds, and frequency. However, the high switching frequency of SiC MOSFETs can increase the losses of the power inverter, resulting in an increase in the temperature, which will limit the performance of power inverters. The improvement of power module performance is mainly controlled by optimizing its control methods during operation and improving its cooling system. Currently, the liquid-cooled heatsink used in power modules have disadvantages such as large flow resistance and poor heat dissipation performance. In order to enhance the performance of the heatsink, this study first established a three-dimensional finite element model of SiC MOSFETs power module based on a pin fin heatsink. The accuracy of the model was verified by numerical and experimental methods. Secondly, based on numerical analysis, a multi-objective topology optimization method for the power module liquid-cooled heatsink is proposed. This method takes heat exchange and fluid dissipation energy as the objective function and uses weight factors to adjust the influence of each on the objective functions. Additionally, the temperature distribution of the heatsink is considered to optimize its performance. Finally, the numerical results show that the topology-optimized heatsink exhibits better performance at high coolant volumetric flow rates. When the coolant volumetric flow rate is 14 L/min, the pressure drops of topology-optimized heatsink is reduced by 63.94 % and the junction temperature of the power module is reduced by 0.24 % compared with the pin fin heatsink. This topologically optimized heatsink could be helpful to improve the performance of existing power module heatsinks.

Molecular Diodes Induced by a Schottky Barrier with a Gold-Silicon Doped Electrode.

To create complementary metal oxide semiconductor compatible molecular devices, more insights into the electrode property regarding its metal/semiconductor doping level and creating a functional molecular device are required. In this work, we constructed an EGaIn/alkanethiol/Au-Si molecular diode (with a rectification ratio R of 50.70) induced by Schottky barriers within a gold-silicon doped electrode instead of the functional property of molecules. The relationship between the rectification ratio and the number of methylene units in alkanethiol was analyzed, revealing a gradual increase in the ratio from 3.33 for C6H14S to 50.70 for C16H34S. The rectification ratio of the junction is well modulated by the temperature due to the change in the Schottky barrier. Such a mechanism is explained by the energy band diagrams of the surface space charge region and a combination of density functional theory and Keldysh-Green formalism calculations.

Density-functional theory study of SnSe/GeSe heterostructure for gaseous sulfur hexafluoride decomposition products sensing

Partial discharge, local overheating and other factors will lead to the decomposition of superior dielectric gas sulfur hexafluoride (SF6) used in gas insulated substations (GIS). Detecting gaseous sulfur hexafluoride (SF6) decomposition products by gas sensors to diagnose early latent insulation failures is a potential approach to guarantee safety and reliability of gas insulated substations (GIS). However, the main difficulties in the detection of SF6 decomposition products lie in sensitivity, operating temperature and sulfur poisoning of the sensor. Metal oxide selenides (MOSs)-based gas sensors suffer from high working temperature, long recovery time, and sulfur poisoning. Two dimensional selenides-based chemiresistor-type gas sensors have been reported to detect certain gases at room temperature. Compared with pristine materials, heterostructures usually have narrower band gaps and higher carrier mobility which promise low power and sensitivity. In this work, a SnSe/GeSe van der Waals heterostructure model is constructed and optimized to investigate the gas sensing properties by density functional theory (DFT) calculations. Compared with the pristine SnSe and the pristine GeSe, the SnSe/GeSe heterostructure exhibits huge adsorption energy and comparatively large charge transfer to the SF6 decomposition gases. The band structure analysis, charge analysis, electron localization function (ELF), and density of states (DOS) analysis suggest that the excellent sensing properties are contributed to the synergistic effect between the SnSe and the GeSe layers: both the layers transfer charge and orbitally interact with gas molecules. Besides, physical adsorption of the SF6 decomposition gases on SnSe/GeSe heterostructure avoids sulfur poisoning of the material, promising the recoverability and repeatability of detection. This study provides theoretical bases for the repeatable detection of SF6 decomposition products by SnSe/GeSe heterostructures and its potential in the design of electronic nose.

SiO2‐GaN Interface Improvement by Wet Cleaning and In Situ Annealing for GaN MOS Transistors

Herein, ex situ wet cleaning and in situ high‐temperature annealing of GaN surfaces prior to low pressure chemical vapor deposition (LPCVD) of the SiO2 gate oxide, aiming at effective SiO2‐GaN interface engineering for channel improvement of metal–oxide semiconductor (MOS) transistors, are investigated. Additionally, the combination of in situ annealing and gate oxide deposition in an LPCVD tool provides the advantage of an industrially preferred batch process. A strong impact of the pretreatments on the interface state density and flatband voltage of the fabricated n‐type GaN MOS capacitors is demonstrated. Combined HF wet cleaning and NH annealing result in a low peak interface state density and a close to ideal C–V curve with a nearly ideal flatband voltage . Furthermore, the I–V characteristics exhibit a positive voltage shift of the current onset and substantially reduced I‐V hysteresis, i.e., negligible temporary charging. Physical root causes are assumed to be reduced contamination due to nondestructive yet efficient HF cleaning combined with subsequent high temperatures and the reduction of near‐interface, quasi‐permanent traps due to the saturation of dangling bonds by the annealing in hydrogen‐containing atmosphere.

Review of Carbon Nanotube Field Effect Transistor for Nanoscale Regime

Background: The need for high performance, small size, low delay, low power consumption, and long battery backup of portable systems is increasing with the advancement of technology. Many features of portable systems can be improved using scaling methods. In the scaling process, reducing the size of devices causes serious difficulties, including the short channel effect (SCE) and leakage current, which degenerates the characteristics of the systems. Objective: In this review paper, a trending carbon nanotube field effect transistor (CNTFET) technology is discussed in detail. CNTFET can replace the conventional metal oxide semiconductor field effect transistor (MOSFET) technology to overcome the SCE problems in the nanoscale regime and also meet the requirements of portable systems. Methods: The CNTFET is an extremely good nanoscale technology due to its one-dimension band structure, high transconductance, high electron mobility, superior control over channel formation, and better threshold voltage. This technology is used to construct high-performance and low-power circuits by replacing the MOSFET technology. CNTFET in comparison to MOSFET takes the carbon nanotube (CNT) as a channel region. Results: The value of threshold voltage in CNTFET changes with the diameter of CNT. The threshold voltage of the devices controls many parameters at the circuit-level design. Hence, the detailed operation and the characteristics of CNTFET devices are presented in this review paper. The existing CNTFET-based ternary full adder (TFA) circuits are also described in this review paper for the performance evaluation of different parameters. Conclusion: CNTFET technology is the possible solution for the SCE in the nanoscale regime and is capable to design efficient logic circuits. The circuits using the CNTFET technology can provide better performance and various advantages, including fast speed, small area, and low power consumption, in comparison to the MOSFET circuits. Thus, CNTFET technology is the best choice for circuit designs at the nanoscale.

Sol-gel-derived WO3 thin films with structure-dependent NO2 sensing properties

The structure of metal oxide thin films can greatly affect their gas sensing properties. However, the structure-property relationship has not been fully established for the NO2 sensing properties of WO3 thin films. In this study, WO3 thin films with two distinct structures have been prepared by the sol-gel technique via employing two different precursor sols. Dense and porous WO3 thin films were successfully prepared as tungsten and WCl6 was used as the precursor source, respectively. Both WO3 thin films are exclusively sensitive to NO2 as low as 80 ppb. Porous WO3 thin films exhibit higher response toward NO2 but slower response/recovery kinetics as compared to the dense ones. Hall measurement and electrochromic coloration confirm the higher carrier mobility in the porous WO3 thin films. The response/recovery kinetics is found to be determined by the gas-solid reaction (receptor function), which is combinedly influenced by the porosity and grain size of the WO3 thin films.

Photocatalytic degradation of Metformin using TiO2-CuO heterojunctions synthesized by green chemistry and immobilized on beach sand granules in fluidized bed annular photoreactor (FBAP)

This research is focused on the degradation of metformin by heterogeneous photocatalysis using TiO2-CuO heterojunctions deposited on beach sand granules in a pilot-scale fluidized bed annular photoreactor (FBAP). The precursor metal oxides were prepared by green chemistry using an aqueous extract of Moringa (Moringa Oleifera) and the heterojunctions by ultrasound-assisted wet impregnation for subsequent immobilization through a two-step immersion/calcination methodology. Batch tests showed a synergistic effect of the inorganic substrate due to its inherent adsorption. Besides, TC1 heterojunction (1wt.% of CuO) represents the best option for deposition due to its optical, morphological, and textural properties and favors its photocatalytic activity. Also, an optimal dose of the active phase of 1.0g/L was identified, guaranteeing this load for the granular catalyst with 4wt.% (g of catalyst/g of beach sand).On the other hand, the values for the pHzpc were 6.45 and 7.26 units, allowing to determine optimal operating pH of 7 and 8 units, respectively, which is attributed to the interaction between the surface loads and the metformin-derived species present in the sample. Optimal values of 18.7L/min achieved a maximum efficiency of 74.8% and 3.0wt.% for volumetric flow and the TC1/S mass ratio, respectively; these operation parameters significantly influence the degradation efficiency. Further, the reaction rate was slightly higher for powdered samples against immobilized heterojunctions due to the mass transfer limitations, which generated a difference in performance close to 2.7%. On the other hand, the reaction byproducts identified were MBG and 4,2,1-AIMT, which are harmless to the biological model C. elegans. Despite this, the segregated nanomaterials and the metal ions leached during the metformin removal generated lethal toxicity. These results reveal the proposed reactor's high potential for treating effluents contaminated metformin and other organic compounds using a granular catalyst with stable performance, including a centrifugation step that removes the segregated nanomaterials.

Defect-controlled fabrication of reduced graphene oxide/ZnO/PMMA-based solid-state optical limiting filters with SA/RSA switching property

A solid-state optical limiting filter was fabricated by noncovalently functionalizing a graphene-based nanocomposite with a polymer. Graphene oxide was reduced by varying reducing agent concentration and functionalized with metal oxide nanoparticles to enhance electronic transitions and third-order nonlinear optical characteristics. The nanocomposite was dispersed over the PMMA polymer framework, and thin films with μm-scale thickness were fabricated using the dip coating method. XRD analysis confirmed the wurtzite crystal structure of ZnO nanoparticles and the amorphous nature of PMMA. The carbon structural integrity was analyzed using Raman spectra. Linear optical studies revealed a redshift in the π-π* transition peak in rGO, suggesting enhanced conjugation. Third-order nonlinear refraction and absorption properties were assessed using the Z-scan technique, revealing a switching behavior in nonlinear absorption at different input intensities. An increase in the relative concentration of sp2 domains enhanced the nonlinear absorption. Optical limiting potential, determined using open aperture Z-scan data, yielded a threshold value of 0.066 GW/cm2. This study aims to develop a solid-state optical filter with a high laser damage threshold by adjusting the reduction rate, tuning defect levels, and analyzing its effect on the optical limiting potential.

Impact of Gd-Substitution on Structural, Dielectric, Spectroscopic, Raman, and Photo luminance Properties of Ba0.4Sr0.6Co2Fe16O27 Ceramics

This paper represents a detailed study of Gd3+ substitutions on Structural, Dielectric, Spectroscopic, Raman, and Photo luminance Properties of Ba0.4Sr0.6Co2Fe16O27 magnetic oxides were prepared using the sol-gel auto combustion method. All of these specimens were sintered at 1100 ºC for five hours. X-ray diffraction analysis (XRD) confirmed the single-phase detection and structural analysis. The lattice parameters a and c show the insignificant behavior 5.893-5.933 Å, and 32.049-32.476 Å with the concentration of gadolinium ions. The crystallite size ranged from 25 to 30 nm, demonstrating a growing tendency as Gd-substitution was enhanced. The discrepancy in the ionic radii of iron (Fe3+) and substituent elements (Gd3+) is the cause of the variation in cell volume and lattice constants. FTIR spectroscopy confirmed the presence of absorption bands (590 and 3000 cm-1) for prepared BaSr-based W-type hexa-ferrites. The vibrational bands of metal oxide ions are responsible for the 590 and 685 cm-1 peaks. The Raman spectrum showed six discrete, brittle peaks: 320, 440, 620, 690, 1300, and 1600 of synthesized nanomaterials—the dielectric constant and dielectric loss increase by substituting the Gd3+ ion. The dielectric parameters and dielectric loss at higher frequencies suggest that the prepared material may be excellent for switching, sensing, and high-frequency applications.

Biotite and ZnO embedded carbon aerogel composite for enhanced photocatalytic activity to degrade ciprofloxacin under sunlight stimulation

This study was explored the photocatalytic efficiency of biotite and ZnO embedded carbon aerogel (CA) photocatalyst to degrade ciprofloxacin (CIP) antibiotic from an aqueous medium by sunlight harvesting. CA came from waste newspaper through pyrolysis technique. Biotite was extracted from Bramapurta River's sand through high-tension magnetic separation techniques. The developed catalyst was characterized by applying FESEM, EDS, XRD, and XPS. The bandgap (1.69 eV) of the catalyst was determined from Tauc's plot. The photocatalytic study showed that, optimum degradation was achieved at 98.471 %, 84.576 %, 77.997 % and 59.607 % for 2, 5, 10 and 20 mg/L CIP containing solution respectively in 180 min at its natural pH applying only employing 0.25 g/L dosage. Moreover, in the pH study, catalyst showed maximum degradation 88.773 % for 5 mg/L CIP containing solution at pH 7 exposing the same irradiation time and dosage. The degradation followed pseudo-first-order kinetics with a maximum rate constant of 0.01831 min−1 which attributes to the first degradation of CIP through ROS. The scavenger test suggested that •OH− and e− played a vital role in the photodegradation process. Regeneration studies confirmed that photocatalysts showed better degradation efficiency until five cycles. Fusion of metal oxides in the catalyst might play a vital role in the multiple photodegradation cycles without losing stability of the composite. FESEM, EDS, and XPS characterization of the spent catalyst was performed for understanding its morphological and chemical change. An antimicrobial study was performed to confirm its efficiency against of gram-negative bacteria (E. coli) and gram-positive bacteria (S. aureus), which suggested that the catalyst is very effective in destroying gram-negative bacteria compared to gram-positive bacteria.

Highly Efficient Aerobic Epoxidation of Styrene using Mesoporous Co-Ni Catalysts

This work reports the synthesis and characterization of mesoporous cobalt-nickel mixed metal oxide catalysts with varying Co:Ni ratios using an inverse micelle template self-assembly method. Their structural and morphological properties and catalytic performance in styrene epoxidation were evaluated. Among them, the 73CoNi-250 catalyst (Co: Ni70:30mol/mol%, calcined 250°C) exhibited a unique flower-like morphology and the highest surface area, which XPS analysis linked to a higher concentration of oxygen vacancies. Notably,73CoNi-250 demonstrated exceptional catalytic activity for styrene epoxidation, achieving near-complete styrene conversion (>99%) and high selectivity (94%) for styrene epoxide under mild reaction conditions without the need for oxidants such as peroxides. Furthermore, the catalyst exhibited excellent reusability (≥ 4 cycles) without significant activity loss or changes in mesoporosity. Kinetic studies revealed a first-order reaction profile and a significantly enhanced rate constant compared to the best-reported values (fivefold) in the literature, further underlining the catalyst's efficiency, and emphasizing the environmentally friendly approaches in chemical synthesis.

Density-functional theory study of SnSe/GeSe heterostructure for gaseous sulfur hexafluoride decomposition products sensing

Partial discharge, local overheating and other factors will lead to the decomposition of superior dielectric gas sulfur hexafluoride (SF6) used in gas insulated substations (GIS). Detecting gaseous sulfur hexafluoride (SF6) decomposition products by gas sensors to diagnose early latent insulation failures is a potential approach to guarantee safety and reliability of gas insulated substations (GIS). However, the main difficulties in the detection of SF6 decomposition products lie in sensitivity, operating temperature and sulfur poisoning of the sensor. Metal oxide selenides (MOSs)-based gas sensors suffer from high working temperature, long recovery time, and sulfur poisoning. Two dimensional selenides-based chemiresistor-type gas sensors have been reported to detect certain gases at room temperature. Compared with pristine materials, heterostructures usually have narrower band gaps and higher carrier mobility which promise low power and sensitivity. In this work, a SnSe/GeSe van der Waals heterostructure model is constructed and optimized to investigate the gas sensing properties by density functional theory (DFT) calculations. Compared with the pristine SnSe and the pristine GeSe, the SnSe/GeSe heterostructure exhibits huge adsorption energy and comparatively large charge transfer to the SF6 decomposition gases. The band structure analysis, charge analysis, electron localization function (ELF), and density of states (DOS) analysis suggest that the excellent sensing properties are contributed to the synergistic effect between the SnSe and the GeSe layers: both the layers transfer charge and orbitally interact with gas molecules. Besides, physical adsorption of the SF6 decomposition gases on SnSe/GeSe heterostructure avoids sulfur poisoning of the material, promising the recoverability and repeatability of detection. This study provides theoretical bases for the repeatable detection of SF6 decomposition products by SnSe/GeSe heterostructures and its potential in the design of electronic nose.

Synthesis of Mo–Cr Mixed Metal Oxide Catalyst Based on Pentagonal Unit Assembly and Selective Oxidation of Ethanol

Synthesis of Mo–Cr Mixed Metal Oxide Catalyst Based on Pentagonal Unit Assembly and Selective Oxidation of Ethanol

CuMn1.7Fe0.3O4 – RE2O3 (RE=Y, Gd) bilayers as protective interconnect coatings for Solid Oxide Cells

Efficient replacement of materials based on critical elements such as cobalt is one of the greatest challenges facing the field of solid oxide cells. New generation materials, free of cobalt show potential to replace conventional materials. However, these materials are characterized by poor ability to block chromium diffusion. This article described the study of CuMn1.7Fe0.3O4 (CMFO) spinel combined with single metal oxide (Y2O3 or Gd2O3) thin films as protective coatings for steel interconnects. CMFO was examined using XRD and TPR. Coated steel samples were oxidized in an air atmosphere at 700 °C for 4000h. The coatings and oxide scale microstructures and cross-sections were examined by CRI, XRD, and SEM-EDX. The electrical properties of the steel-coating system were evaluated using Area Specific Resistance measurements. Based on the results obtained, it can be concluded that the use of thin layers of rare earth oxides allowed for better blocking of chromium diffusion.

Constructing dual sulfite-mediated processes via inner-sphere complexation and photogenerated carrier modulation with Hematite/Fe2TiO5 heterojunction for ofloxacin degradation

Hitherto, various sulfite-based advanced oxidation processes have emerged with particular vantages of low cost and potential for efficient contaminant degradation, which still requires increasing strategies for addressing its drawback. To achieve system-neutral feasibility and overcome the limitations, a metal oxide composite catalyst Hematite/Fe2TiO5 integrated with S-scheme heterojunction was constructed for ofloxacin degradation under S(IV)-visible light conditions. Impressively, the as-built system manifested significant promotion on substrate removal (more than four times the original Fe2TiO5), which indicated the accelerated inner-sphere interactions between catalyst and S(IV) with beneficial Vis contributed primarily to the degradation, demonstrating the dual sulfite-mediated effective pathway through modulated photogenerated carriers and oxy-sulfur radical chain reactions. Additionally, the interfacial enhancement by the heterojunction structure was further investigated by First-principles computation, which confirmed the mechanism of facilitated electron-hole pair separation. Overall, this work reveals the critical mechanism of Vis-induced S(IV)-AOP and provides constructive perspectives to address the limitations of conventional processes.

Impact of Gd-Substitution on Structural, Dielectric, Spectroscopic, Raman, and Photo luminance Properties of Ba0.4Sr0.6Co2Fe16O27 Ceramics

This paper represents a detailed study of Gd3+ substitutions on Structural, Dielectric, Spectroscopic, Raman, and Photo luminance Properties of Ba0.4Sr0.6Co2Fe16O27 magnetic oxides were prepared using the sol-gel auto combustion method. All of these specimens were sintered at 1100 ºC for five hours. X-ray diffraction analysis (XRD) confirmed the single-phase detection and structural analysis. The lattice parameters a and c show the insignificant behavior 5.893-5.933 Å, and 32.049-32.476 Å with the concentration of gadolinium ions. The crystallite size ranged from 25 to 30 nm, demonstrating a growing tendency as Gd-substitution was enhanced. The discrepancy in the ionic radii of iron (Fe3+) and substituent elements (Gd3+) is the cause of the variation in cell volume and lattice constants. FTIR spectroscopy confirmed the presence of absorption bands (590 and 3000 cm-1) for prepared BaSr-based W-type hexa-ferrites. The vibrational bands of metal oxide ions are responsible for the 590 and 685 cm-1 peaks. The Raman spectrum showed six discrete, brittle peaks: 320, 440, 620, 690, 1300, and 1600 of synthesized nanomaterials—the dielectric constant and dielectric loss increase by substituting the Gd3+ ion. The dielectric parameters and dielectric loss at higher frequencies suggest that the prepared material may be excellent for switching, sensing, and high-frequency applications.

Harnessing the power of temperature gradient-enhanced pyroelectricity: self-powered temperature/light detection in Ce-doped HfO2 ferroelectric films with downward spontaneous polarization

Ferroelectric materials are ideal for self-powered sensors in Internet of Things (IoT) and high-precision detection systems due to their excellent polarization properties. Compatibility with miniaturization, high-density systems, and complementary metal oxide semiconductor (CMOS) processes is crucial for their widespread adoption. HfO2-based ferroelectric films show potential in self-powered pyroelectric sensors as their thinness enables effective temperature and light detection. However, the disordered ferroelectric domain distribution limits their pyroelectric performance and hampers the development of highly integrated self-powered pyroelectric devices. This report investigates the temperature and light detection capabilities of Ce-doped HfO2 ferroelectric films, which exhibit as-grown spontaneous polarization in the downward direction, making them a promising option for self-powered pyroelectric sensors. The findings provide robust evidence that the introduction of a temperature gradient significantly enhances pyroelectricity. In addition, their applications in the detection of hot/cold wind and breathing have been proved. Notably, the 30 nm thick Ce-doped HfO2 ferroelectric film has a high pyroelectric coefficient of about 894.7 μC·m–2·K–1 and enables high-precision detection of changes in temperature of 0.1 K. This study highlights the potential application of HfO2-based ferroelectric films in self-powered sensors with temperature and light detection capabilities, making them a promising candidate for future IoT-based systems and high-precision detection systems.

A Review of Impedance Spectroscopy Technique: Applications, Modelling, and Case Study of Relative Humidity Sensors Development

Impedance Spectroscopy (IS) is a general term for the technique referring to small-signal measurements of the linear electrical response of a domain of interest. This method is based on the analysis of the system’s electrical response to yield helpful information about its domain-dependent physicochemical properties (generally, the analysis is carried out in the frequency domain). Nowadays, there are many areas of application where IS can be used to evaluate or enhance the development of emerging products and processes. As a contribution to this field of research, this paper presents relevant theoretical–practical aspects of the interpretation and analysis of the electrical behavior of materials based on IS and IS modelling. The work starts by historically introducing IS and then goes through different domains of application of the technique, such as Materials Science and correlated areas. Afterwards, an introduction to IS usage for constructing equivalent electrical circuits is presented, aiming at modelling the materials’ electrical behavior, followed by examples from the literature that use the two possible circuit development approaches, the series and the parallel association of circuit elements. Lastly, the authors present a case study of their most recent efforts of a circuit model development of relative humidity (RH) sensors based on heterogeneous mixed metal oxide (MMO) nanostructures, used to understand and identify existing contributions to the overall electrical response of the sensors to moisture; in their case, the electrical response of the MMO sensors was modelled with a high level of superposition between the experimental and fitted data, using a parallel combination of circuit elements, which is an unconventional one.

Ammonia decomposition over La-doped Al2O3 supported Co catalyst

As the hydrogen source of carbon-free fuel cells, the key to realize the green and low-energy decomposition hydrogen production process is to select materials with excellent catalytic performance for ammonia dehydrogenation. In this study, the rare earth element lanthanum (La) was doped onto the surface of Al2O3 by the impregnation method. The aforementioned material was subsequently used as a new material for the synthesis of single metal Co catalysts that catalyzed ammonia decomposition. Various characterization techniques (XRD, HRTEM, N2 physical adsorption-desorption, ICP, XPS, SEM, H2-TPR) were employed to investigate the relationship between the structure and performance of Co/La–Al2O3 catalysts. The findings indicated that the 10Co/La(5)-Al2O3 catalyst was the most active. Under the conditions of 550 °C and 9000 mL h−1·gcat−1, the conversion of ammonia reached 90 %, and the yield of hydrogen reached 8.9 mmol·gcat−1·min−1. A perovskite-type metal oxide layer of LaAlO3 was generated on the surface of Al2O3 support after doping the appropriate amount of lanthanum (5 %), which directly affects the catalytic performance of the catalyst. The small amount of LaAlO3 optimized the strong interaction between the metal Co and the supports, thereby enhancing catalytic performance. While stabilizing the active component Co, XPS and H2-TPR also implied that the presence of La could enhance the electron transfer between the support and Co, as well as facilitate the desorption of nitrogen and hydrogen products, therefore, the low temperature activity of Co/La–Al2O3 catalyst can be improved. The ammonia decomposition efficiency of the catalyst doped with 5 % wt La was much higher than that of the catalyst without La incorporation. The simple modified support developed by us, which loads a monoatomic Co catalyst, provides a new approach for the development of high-activity transition metal catalysts.