Long-term Stability Measurements Research Articles

Developing high-performance oxygen electrodes for intermediate solid oxide cells (SOC) prepared by Ce0.8Gd0.2O2−δ backbone infiltration

Gd0.2Ce0.8O 2−δ (GDC) porous backbone infiltration with La0.6Sr0.4CoO3−δ (LSC), PrOx and LSC: PrOx as a composite oxygen electrode for intermediate solid oxide cells are conducted within the scope of this work. Samples were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and electrochemical impedance spectroscopy (EIS). A uniform distribution of the infiltrated material inside the backbone and at the electrolyte-backbone interface was achieved. EIS measurements on the prepared symmetrical samples showed electrode polarization resistance (Rp) values of 0.029 Ω.cm², 0.23 Ω.cm², and 0.44 Ω.cm² for LSC, LSC: PrOx, and PrOx at 600 °C, respectively. Long-term stability measurements at 600 °C for 100 h showed a slight increase in polarization resistance during the measurement period. Fuel cell measurements of commercial cells (Elcogen) with porous oxygen electrode consisting of GDC infiltrated with LSC showed an increase in power density compared to the reference cell with a value of 0.53 W.cm− 2 obtained at 600 °C. It is proven that infiltration via polymeric precursor into porous scaffolds as backbone oxygen electrode layer is effective and convenient method to develop high performance and stable solid oxide cells.

Characterising and tackling thermally induced zero-drift in displacement measuring interferometry using temperature-controlled enclosure

Abstract Our research efforts in displacement measurement interferometry focused on long-term drifts initiated an extended experimental investigation in the interferometric assemblies of our design. We aimed to analyze, characterize and tackle the long-term measurement stability, expressed as the zero-drift, with particular attention to the thermal effects. For the experimentation, we developed a thermostatic chamber equipped with active temperature regulation, an array of sensors and control electronics. With either the finely stabilized temperature or with the thermal cycling, we can carry out a range of investigations: verification of modified design or prototype interferometers, testing of production pieces, characterization of integrated assemblies and units in terms of the zero drift and the susceptibility to thermal effects—the temperature sensitivity ( δ L / δ T , expressed in nm ⋅ K−1). With these experimental studies, we demonstrate the potential of the zero drift studies to contribute to the development and broader expansion of interferometric instrumentation.

Safety, Feasibility, and Utility of Digital Mobile Six-Minute Walk Testing in Pulmonary Arterial Hypertension: The DynAMITE Study.

Pulmonary arterial hypertension (PAH) is a life-threatening progressive cardiopulmonary disease associated with high morbidity and mortality. Changes in the six-minute walk test (6MWT) provide prognostic information and help guide treatment decisions for PAH. However, since 6MWT requires in-clinic visits, clinical interventions to address disease progression may be delayed. Wearable technologies could reduce this delay by allowing the performance of 6MWT in the community and delivering data to clinicians remotely. To perform a pilot study to determine the safety and feasibility of performing 6MWT in PAH outpatients using a wearable app-based tool. PAH patients recruited at Stanford University were provided an Apple Watch with an app to perform daily, self-administered 6MWT over 12 weeks. Bland-Altman plots and correlations were used to assess the agreement and reliability of in-clinic vs. app-based 6MWT data at the beginning and end of the 12-week trial. From 55 PAH participants, we collected 3,139 app-recorded walks during 979.7 patient-weeks of exposure. On average, participants performed 3±2.3 weekly walks. No serious adverse events were reported. App-derived walk distance was highly correlated ( r ≥ 0.9) to the baseline in-clinic 6MWD and showed excellent reliability (ICC=0.9). Correlation and agreement were significantly lower at the 12-week follow-up visit. App-derived metrics beyond 6MWD showed promising associations with disease status. App-based outpatient 6MWT is feasible, safe, reasonably accurate, likely clinically relevant, and reliable in PAH patients but long-term measurement stability may be a concern. App-derived digital measures beyond distance show promise for future applications.

Analysis and suppression of the Rb resonance frequency error in NMR angular velocity sensor

The nuclear magnetic resonance (NMR) angular velocity sensor has the potential for high precision measurement in small volumes, which measures the 129Xe and 131Xe precession frequencies to obtain the angular velocity with respect to an inertial reference frame. One of the key challenges in frequency measurement is the long-term stability of the measured signal phase. The measured signal is acquired by applying a carrier magnetic field along the z-axis and demodulating the carrier signal at its frequency, which is typically fixed. However, fluctuations in light shifts and static magnetic fields can lead to instabilities in the Rb resonance frequency, consequently impacting the measurements of phase and precession frequencies of 129Xe and 131Xe. To address this issue, an analysis of the Rb resonance frequency error is conducted, and a suppression scheme based on carrier frequency correction is provided. This scheme can mitigate the effect of Rb resonance frequency fluctuations without further suppressing fluctuations of light shifts and static magnetic fields. The experiment demonstrates a 53.5 % reduction in the precession frequency error between 129Xe and 131Xe and a 59.0 % decrease in bias instability. This scheme can improve the long-term stability of 129Xe and 131Xe precession frequency measurements, thereby enhancing the performance of the NMR angular velocity sensor.

Comprehensive analysis of the magnetic field closed-loop control system in SERF atomic magnetometer

Benefiting from the capability to measure and suppress magnetic field interferences in situ, the closed-loop magnetometer system has garnered significant attention. In this paper, the low-pass filtering link is analyzed theoretically and experimentally for the first time within the framework of the single-beam spin exchange relaxation free atomic magnetometer system (the object to be controlled). The analysis not only elucidates its impact on the closed-loop system but also establishes optimal operating parameters through a comprehensive consideration of factors such as steady-state error, bandwidth, and other metrics. A comparison and analysis of the direct output signal of the system with the controller output signal reveal the necessity of using the controller output as the closed-loop system’s output, supported by the amplitude and frequency response characteristics of the output signal. The paper introduces evaluation indicators essential for comparing the long-term measurement stability of open- and closed-loop systems, and it explores the correlation between the output signals of the open- and closed-loop systems and the cardio-magnetic input signals. Finally, the calibration methods for multi-channel closed-loop magnetometers are discussed.

An organic–inorganic hybrid method to fabricate bimetallic phosphide nanospheres as efficient electrocatalyst for hydrogen evolution reaction

Hydrogen evolution reaction (HER) serves as a crucial half reaction in electrolytic water splitting. Pt is deemed to the most active HER electrocatalyst, but the scarcity and high cost of Pt limit its massive application. Developing efficient, low-cost and well-structured HER catalysts is quite vital for advancing the development of water electrolysis technology. Herein, we present a facile organic–inorganic hybrid method to achieve a novel bimetallic phosphide of MoP-RuPx/NPC catalyst, showing superior electrocatalytic activity with an overpotential of 24 and 94 mV at 10 mA cm−2 in alkaline and acid media, respectively. Moreover, MoP-RuPx/NPC also exhibits an outstanding electrochemical stability with a negligible degradation in HER activity after long-term stability measurements. The eminent electrocatalytic performance of MoP-RuPx/NPC catalyst should be ascribed to the high surface specific area, multiple heterogeneous interfaces, strong electronic synergistic effect between MoP and RuPx, and abundant defects. The organic–inorganic hybrid strategy implemented in this work can be used for synthesizing other bimetallic phosphide catalysts.

From batch to flow: the effect of pH, current, and the crystal facets of Cu2O on electrochemical CO2 reduction

The electrochemical CO2 reduction, on various Cu2O crystal facets, was studied in a flow electrolyzer. The influence of pH, and current was optimised and a long-term stability measurement highlights the issue of GDE flooding.

A novel Pt modified AlGaN/Si double-junction nanostructure for stable and self-powered solar blind photoelectrochemical photodetection

Simultaneously searching for self-powered, efficient, stable photoelectrode is the key to realizing the next-generation energy-efficient and sustainable integrated solar blind photoelectrochemical (PEC) photodetector. In this work, a Pt modified AlGaN/Si double-junction nanostructure with an n++ AlGaN/p++ AlGaN tunnel junction (TJ) and a AlGaN/Si junction is reported to achieve stable and self-powered solar blind photodetection. PEC tests demonstrate that the photocurrent density of the Pt modified AlGaN with n++ AlGaN/p++ AlGaN TJ photoelectrode can reach up to −56.1 μA/cm2 under 255 nm light irradiation with 1.1 mW/cm2 at 0 V bias versus a Pt counter electrode in a three-electrode configuration. Time-steady photoluminescence and XRD spectra are carried out and confirm the inherent optical and physical properties of this nanostructure. In addition, the multicycle and long-term stability measurement shows an excellent switching behavior even after being placed in the air for one month with a photocurrent density of −44.9 μA/cm2 (80% of its initial photocurrent). Furthermore, the PEC performance of the Pt modified AlGaN with n++ AlGaN/p++ AlGaN tunnel junction photoelectrode is evaluated in different light wavelengths, light intensities, bias potential and H2SO4 concentrations. These results demonstrate that the as-prepared photoelectrode has a great potential application in stable self-powered solar blind photodetector.

Influence of pore size on mass transport: Bifunctional MnOx-coated nickel foam vs carbon corrosion prone commercial GDE in alkaline electrolyte

A promising step towards a carbon-free gas diffusion electrode (CF-GDE) design for alkaline applications is shown in this work. MnOx´s are electrodeposited on nickel foam by varying the settings, and then they were annealed at 300 °C. These CF-GDEs were characterized and compared with a commercial carbon-based GDE (GDEref). Samples were analyzed by XRD, SEM, X-ray tomography, contact angle method, nitrogen sorption, and electrochemical methods. Electrochemical impedance spectroscopy confirmed the higher reactant transport of CF-GDEs during OER and ORR. The large pore size of the CF-GDE substrate (nickel foam) results in a high supply of catalyst sites deep inside the CF-GDE. The transport distance of gaseous O2 is also reduced since the thin electrolyte film is at the gas bulk of the CF-GDE. The catalytic bifunctionality was additionally examined by galvanostatic measurements at 5 and 10 mA cm− 2. A promising CF-GDE exhibited 0.43 V ηOER and −2.43 V ηORR at 10 mA cm−2. Lastly, long-term stability measurements of 2100 cycles at 1.5 V (OER) and −0.75 V (ORR) vs. Hg/HgO in 1 M NaOH show the carbon corrosion of GDEref (60% current density loss) and a stable current density of CF-GDE.

The relationship between labial soft tissue changes and jumping spaces after immediate implant placement and restoration in the anterior maxilla: A prospective study.

Oral implants have been increasingly used in the treatment of edentulous patients or those with dentition defects due to reliable treatment procedure and favorable long-term prognosis. We investigated the changes of labial soft tissue contours with different jumping spaces after immediate implant placement and restoration (IIPR) in the maxillary esthetic area and also provided a long-term stability measurement for the changing trend of soft tissue contour. All patients had been separated into three groups based on the jumping space: group A (horizontal defect dimension [HDD] 2 mm), group B (2 mm < HDD 3 mm), and group C (HDD > 3 mm) and the digital impressions were obtained in the first, third, and sixth month after the operation. The changes of gingival mucosa levels, the average thickness of soft tissue contour volume, and the linear change of submarginal level decreased gradually across the three groups, with the largest change of submarginal level being at 5mm. The size of the jumping space was moderately negatively correlated with the level and average thickness of gingival mucosa and the linear changes of 3 mm and 5 mm under gingival margin, while there was no significant correlation with pink esthetic score (PES) and the linear change of the 1 mm under the gingival margin. Generally, IIPR of upper anterior teeth can achieve esthetic satisfaction, and the level of soft tissue around the implant can be well preserved.

Understanding the effect of MXene in a TMO/MXene hybrid catalyst for the oxygen evolution reaction

Very recently, it has been reported that mixed transition metal oxide (TMO)/MXene catalysts show improved performance over TMO only catalysts for the oxygen evolution reaction (OER). However, the reasoning behind this observation is unknown. In this work mixed Co(OH)2/Ti3C2Tx were prepared and characterized for the OER using ex situ and operando spectroscopy techniques in order to initiate the understanding of why mixed TMO/MXene materials show better performances compared to TMO only catalysts. This work shows that the improved electrocatalysis for the composite material compared to the TMO only catalyst is due to the presence of higher Co oxide oxidation states at lower OER overpotentials for the mixed TMO/MXene catalysts. Furthermore, the presence of the MXene allows for a more mechanically robust film during OER, making the film more stable. Finally, our results show that small amounts of MXene are more advantageous for the OER during long-term stability measurements, which is linked to the formation of TiO2. The sensitivity of MXene oxidation ultimately limits TMO/MXene composites under alkaline OER conditions, meaning mass fractions must be carefully considered when designing such a catalyst to minimize the residual TiO2 formed during its lifetime.

A Temperature-Insensitive Resonant Low-Pressure Microsensor Based on Au–Si Eutectic Wafer Bonding

This article shows a temperature-insensitive resonant low-pressure microsensor based on Au–Si eutectic wafer bonding. The microsensor comprised an silicon-on-insulator (SOI) wafer as the sensitive part, and a silicon cap packaging the SOI wafer in vacuum through Au–Si eutectic bonding to lower the thermal stresses and reduce the temperature sensitivity as no coefficient of thermal expansion mismatch exists between the SOI wafer and the silicon cap. Meanwhile, the silicon cap can counterbalance the thermal stresses induced by Au layer and Ti getter, lowering the temperature sensitivity of the microsensor from 7 to 2 Hz/°C with the thickness increasing from 300 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1500 \,\mu \text{m}$ </tex-math></inline-formula> based on numerical simulation. Characterization results showed that the low-pressure sensitivities of the microsensors were about ±6 Hz/Pa, and the temperature sensitivities were about 5 Hz/°C, indicating the microsensor was insensitive to temperature based on Au–Si eutectic wafer bonding. Furthermore, high accuracies (measurement errors within ±3.5 Pa) and satisfactory long-term stability (measurement errors within ±3 Pa after one month) were obtained under the low pressures from 0.1 to 1 kPa and temperature from −40 °C to 80 °C, indicating the better performances than previous works for the low-pressure microsensors.

Acid@base co-sensitization strategy for highly efficient dye-sensitized solar cells

Two new base dyes bearing pyridyl acceptor ( Py-1 and Py-2 ) are synthesized, which are respectively co-sensitized with an acid dye containing cyanoacetic acceptor ( NP-1 ), constructing the acid@base co-sensitized solar cells (co-DSSCs). The lightspot is that the carboxylic and pyridyl groups could anchor onto the Brønsted-acid and Lewis-acid sites of TiO 2 surfaces, respectively. The research results show that the combination of these acid and base dyes is beneficial to suppress the competitive adsorption between dyes, thus increasing the dye coverage on TiO 2 surfaces and decreasing the electron recombination, and further raising the photovoltage; moreover, their complementary spectral responses can significantly increase the photocurrent. Therefore, the acid@base co-DSSC based on NP-1@Py-2 (2:3) delivers the best photovoltaic performances in comparison to the DSSC based on NP-1 , in which the photovoltaic efficiency is increased by 32.5% (from 4.0% to 5.3%). Furthermore, the photovoltaic performances under different irradiation and long-term stability measurements can provide a basis for application evaluation of co-DSSCs. • Synthesize two different π-bridge pyridyl dyes. • Explore a new acid@base co-sensitization system. • Compare the effect of co-sensitized ratios on photovoltaic-device efficiency. • Improve the light-harvesting ability through spectral complementary absorption.

Improving thermal energy storage and transfer performance in solar energy storage: Nanocomposite synthesized by dispersing nano boron nitride in solar salt

Solar salt (SS) is an energy storage material widely used in concentrating solar power (CSP) stations at industrial thermal energy storage (TES) systems in the current. Hence, a conventional high-temperature static melting method was used to prepare nano hexagonal boron nitride-SS (h-BN-SS, BS system) composite materials with different content of nano BN to improve the heat storage and transfer performance of SS. The specific heat (cp) of 1.81 J·g−1·K−1 was obtained at nano BN content of 0.8 wt% (sample BS6), which had increase of 16.03% compared with pure SS (sample BS0). The crystal planes (104) and (221) of nitrate appeared on the surface of nano BN (100), promoted the enhancement of surface energy of whole system. The using temperature zone was widened and thermal conductivity (λ) had been increased by 18.52%. The existence forms of nano BN hadn't changed at high temperature, and the cation environment around NO3− of BS0 and BS6 were changed after adding nano BN demonstrated by high temperature Raman spectroscopy. Moreover, BS6 had excellent thermal stability at long-term thermal stability measurement within 7200 min. The observations suggested that nano BN may serve as promising additive for solar energy storage material toward TES system applications.

Removal of residual compositions by powder engineering for high efficiency formamidinium-based perovskite solar cells with operation lifetime over 2000 h

Defects as a result of structural imperfections and/or extrinsic impurities in the perovskite films have a detrimental effect on efficiency and stability of perovskite solar cells (PSCs). Here, we propose to use pre-synthesized crystalline perovskite with perfect stoichiometry to control and lower the density of defects from precursors by the powder engineering method. Compared with raw materials (i.e., PbI 2 and FAI) based perovskites, the average efficiency of the PSCs fabricated based on these pre-synthesized perovskite precursors increased from 18.62% to 19.85%. Moreover, the unwanted intermediate chemical compositions (i.e., the unreacted phases and residual solvent) in the raw material-based perovskite films were significantly reduced in the pre-synthesized δ-FAPbI 3 and α-FAPbI 3 perovskites according to the secondary ion mass spectroscopy depth profiling results. Finally, we obtained the champion efficiency of 22.76% for α-FAPbI 3 and 23.05% for FAPb(I 0.9 Br 0.1 ) 3 based PSCs. Long-term operational stability measurements of the encapsulated FAPb(I 0.9 Br 0.1 ) 3 based PSCs showed a slow decay and maintained the efficiency about 88% after 1200 h (T 80 > 2000 h). Furthermore, a proof-of-concept integrated perovskite solar module-lithium ion battery-light-emitting diode device was demonstrated. Formamidinium-based perovskite solar cells with a high efficiency over 23% and 2000-h T 80 lifetime were fabricated using pre-synthesized crystalline perovskite powders via powder engineering. • Pre-synthesized crystalline perovskite powder with fewer defects is prepared by the powder engineering method. • Residual compositions are removed, which results in improved efficiency and operational stability. • The highest PCEs of 22.76% for α-FAPbI 3 and 23.05% for FAPb(I 0.9 Br 0.1 ) 3 are achieved by the powder engineering method. • A proof-of-concept perovskite solar module-lithium ion battery-light-emitting diode (PSM-LIB-LED) device is demonstrated.

(Invited) Highly Selective Detection of Propanol and Ethanol Gas Sensing Characteristics of SnO2/NiO and SnO2/NiO/Au Hollowspheres Based Chemiresistive Sensors

IntroductionThe enormous market demands for gas sensors to detect and monitor volatile organic compounds (VOCs) and toxic gases in environmental protection, medical treatment and safety requirements of industry and daily life have motivated enormous awareness in the fabrication of high performance gas sensing materials. Generally, VOCs are considered as low boiling point carbon-comprising materials that can evaporate simply at room temperature and contribute in atmospheric photochemical reactions, such as photochemistry smog and ozone formation. Besides, controlling and detection of these VOCs, such as methanol, ethanol, propanol and acetone is significant because they are considered as widespread concerns for common pollutants in indoor/outdoor air quality and for testing alcohol levels of drivers [1]. In comparison to other VOCS, propanol is less toxic, nonetheless its usage for numerous daily applications, for example hand sanitizer, cosmetics, maybe imagined to be polluting the breathing air. Besides, Iso-propanol was presented to behave as an aesthetic and central nervous system sedative, leading in symptoms that can frighten the mental ability of the individual [2].Yet, the fabrication of the anticipated gas sensor with superior sensitivity, low detection limit, and exceptional long-term stability is still a significant research issue. In addition, the high operating temperatures and poor selectivity often limits the application and commercialization of semiconductor metal oxide (SMO) gas sensors. Thus, this work is directed to improve the selective, sensitivity, stability and reduce the operating temperatures of the metal oxides based sensors, by exploiting SnO2 hollowspheres loaded with various NiO nanoparticles contents and SnO2/NiO loaded with various Au nanoparticles contents synthesized using a simple hydrothermal method. Our findings showed improved stability upon loading SnO2 hollowspheres with various NiO contents. Amongst the various NiO contents, the 0.01 wt.% NiO loaded SnO2 demonstrated higher response and sensitivity towards propanol (C3H7OH) in dry air and in the presence of 40 and 60 % RH at an operating temperature of 150 °C. While the as-fabricated SnO2/NiO/Au (2.5 wt.%) based sensor exhibited a response that is more than 2 times higher in comparison to that of SnO2/NiO (0.01wt. %) and lower operating temperature 75 °C towards ethanol (C2H5OH) and C3H7OH. The long-term stability analyses established that both the fabricated SnO2/NiO (0.01 wt.%) and SnO2/NiO/Au (2.5 wt. %) sensors were very stable towards C3H7OH and C2H5OH after a month in the presence of 40% RH. These findings showed that the current sensors can be employed for detecting C3H7OH and C2H5OH in a vastly sensitive and selective way with insignificant interference from ambient humidity.MethodPorous hollowspheres were synthesized according to the following procedure reported in ref. [3]. While the NiO loaded SnO2 hollowspheres were fabricated using the as-prepared hollowspheres as templates. Gold (Au) loaded NiO/SnO2 hollowspheres were prepared using NiO/SnO2 hollowspheres as template. Detailed synthesis preparation can be found in ref. [4].Sensing preparations and testing of the sensors towards various reducing gases (e.g. CO, CH4, and NH3), volatile organic compounds (C2H5OH and C3H7OH), and an oxidizing gas (NO2) in a background of synthetic dry air were performed according to the procedure in ref [3,4].Results and ConclusionsTo investigate the operational temperature influence on the gas sensing characteristics, the sensing layers were analysed at various operating temperatures (75 to 225 °C). The variations in the gas sensing resistance (Ra) of the SnO2 loaded with various NiO contents and SnO2/NiO loaded with various Au contents as a function of operating temperature were presented. The Ra of the all sensing materials decreased with an increase in operating temperature, except that that of low Ni loading (see Fig. 1A). A decrease could be that when the operational temperature increases more electrons from valence band of the sensing layer will jump to conduction band and accordingly more electrons are available for carrying current, resulting in a decrease of Ra [4]. While the increase in Ra values for SnO2/NiO can be justified by the formation of nanoscale p/n junctions between the NiO and SnO2 phases.We further explored the stability of the SnO2/NiO (0.01 wt.%)-and SnO2/NiO (0.01 wt.%)/Au best performing based sensors in terms of repeatability and long-term stability measurements in dry air and in the presence of relative humidity (RH). The fresh sensor in day one and that tested after 30 days displayed a flawless repeatability of eight successive cycles towards 40 ppm C3H7OH (see Fig. 1B). Based on the findings, after 7 to 30 days, only minimal drift on the repeatability performance was witnessed, while the response increased by almost 8%, validating that our sensor is very stable. Same behavior was observed for the SnO2/NiO (0.01 wt.%)/Au(2.5 wt.%) based sensor [4]. Thus, these findings corroborated that the current sensors are very stable when either exposed to dry air or in real conditions after long exposure to C3H7OH and C2H5OH.

Long-term stability of TVO low-temperature sensors before and after gamma irradiation with a high dose

The long-term stability of well-known TVO sensors before and after gamma irradiation was investigated during almost 17 years. Five of six sensors, calibrated in the temperature range from 3 to 300 K, were selected according to a requirement of their relative accuracy ΔT/T ≤ ± 0.25% at the cryogenic temperature range. Long-term stability measurements made 7.5 years after calibration are in good agreement with this value at 293, 77.3, and 4.2 K. Then these sensors and the sixth sensor, taken as the “worst” one for comparison, were irradiated by the 60Co gamma source at room temperature up to the total dose of about 1 MGy. Noticeable relative temperature shifts (more than ± 0.25%) are revealed for all the sensors after irradiation, and this fact is explained based on the model of structural changes in the volume of the sensitive element. Post-irradiation measurements carried out during 9 years at 293, 77.3, and 4.2 K indicate good stability of the sensors after irradiation.

A LaBr3(Ce) detector system with a simple spectral shift correction method for applications in harsh environments

A prototype LaBr3 detector system with an integrated electronics unit was developed to perform accurate gamma ray spectroscopy in harsh environments. A simple spectral shift methodology was employed in a LaBr3 detector system, which is capable of restoring gamma spectra measured under various temperature conditions within the range of −20 to +50 °C, in real-time. The methodology was tested at various temperatures. The long term stability of measurements using a LaBr3 detector system was also successfully verified.

Zn-Al Mixed Oxides Decorated with Potassium as Catalysts for HT-WGS: Preparation and Properties

A set of ex-ZnAl-LDHs catalysts with a molar ratio of Zn/Al in the range of 0.3–1.0 was prepared using co-precipitation and thermal treatment. The samples were characterized using various methods, including X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy FT-IR, N2 adsorption, Temperature-programmed desorption of CO2 (TPD-CO2) as well as Scanning electron microscopy (SEM-EDS). Catalyst activity and long-term stability measurements were carried out in a high-temperature water–gas shift (HT-WGS) reaction. Mixed oxide catalysts with various Zn/Al molar ratios decorated with potassium showed high activity in the HT-WGS reaction within the temperature range of 330–400 °C. The highest activity was found for the Zn/Al molar ratio of 0.5 corresponding to spinel stoichiometry. However, the catalyst with a stoichiometric spinel molar ratio of Zn/Al (ZnAl_0.5_K) revealed a higher tendency for surface migration and/or vaporization of potassium during overheating at 450 °C. The correlation of the activity results and TPD-CO2 data show that medium basic sites enhance the progress of the HT-WGS reaction.

New 3-D Mn(II) coordination polymer with redox active oxalate linker; an efficient and robust electrocatalyst for oxygen evolution reaction

A novel three dimensional coordination polymer {[Mn(ox)3/2][bap].(H2O)}n, (1) (ox = oxalate, bap = N-benzyl-4-aminopyridinium) is reported in this work as an efficient electrocatalyst for oxygen evolution reaction (OER). 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) based dispersion condition as well as interactions between the adjacent layers of anionic coordination polymer and N-benzyl-4-aminopyridinium were found necessary for the growth and stability of this architecture. Single crystal XRD, IR and elemental analysis confirmed the formation of compound (1). Morphology and thermal stability were evaluated by SEM and TG respectively. Electrochemical studies were carried out in a three-electrode system using 1 coated FTO as a working electrode using 0.1 M KOH solution. The electrochemical investigation showed that 1 produced a current density of 10 mAcm−2 at a relatively low overpotential (η = 404 mV) while a maximum current density of 62 mAcm−2 was achieved. A catalytic onset potential for OER was observed at 1.5 V (vs RHE) and needed overpotential of 258 mV. The catalyst offered a turnover frequency (TOF) of 0.06 s−1 for OER at 404 mV. Long-term stability measurements of 1 were recorded by using chronoamperometry, IR analysis and LS voltammograms for the pristine and post-catalytic 1 coated FTO electrodes that confirmed the durability of the catalyst. The fascinating electrochemical behaviour of 1 toward oxygen evolution reaction can be attributed to its 3D polymeric structure and represents 1 as a robust and efficient catalyst towards OER.