Fast Response, Highly Sensitive and Selective Mixed-Potential H2 Sensor Based on (La, Sr)(Cr, Fe)O3-δ Perovskite Sensing Electrode

Ultra-Low-Power, Extremely Stable, Highly Linear-Response Thermal Conductivity Sensor Based on a Suspended Device with Single Bare Pt Nanowire

The continuous and stable monitoring by sensors is crucial for ensuring the safe utilization of hydrogen due to its inherent high explosiveness. Currently, catalyst aging and oxygen dependence often limit the lifetime of most sensors, which stems from the sensing materials and catalytic reaction in comparison to thermal conductivity sensors. Thermal conductivity sensors possess superior sensing characteristics such as lowpower consumption and exceptional stability attributed to their free-catalysts or free-oxygen nature. Herein, we present an ultralow-power hydrogen-thermal conductivity sensor based on suspended bare platinum nanowires. This sensor incorporates two suspended independent working elements (serpentine/bridge), each of which is thermally decoupled from the substrate. Also, the bridge element operates at significantly lower power levels (the lowest ∼3.32 μW) compared to existing direct-current hydrogen-thermal conductivity sensors. Furthermore, it demonstrates a 99.99% linearity between hydrogen concentration and response under various operating powers. Finally, our sensor shows remarkable stability through a repeatability test (>30,000 cycles). This developed platform provides an optimal structure scheme for integrated sensors with ultralow-power, extremely stable, highly linear-response sensing characteristics, which is expected to be widely used for hydrogen detection and leakage warning under various pipeline distribution systems.

Pt Loading of Phosphorus-Doped Carbon Nanotube Aerogels in Fuel Cell-Type Gas Sensors for Ultrasensitive H2 Detection

A phosphorus-doped carbon nanotube (CNT) aerogel as the support material was loaded with Pt nanoparticles in fuel cell-type gas sensors for ultrasensitive H2 detection. The high surface area of the CNT scaffold is favorable to providing abundant active sites, and the high electrical conductivity facilitates the transport of carriers generated by electrochemical reactions. In addition, the CNT aerogel was doped with phosphorus (P) to further enhance the conductivity and electrochemical catalytic activity. As a result, the fuel cell-type gas sensor using the Pt/CNT aerogel doped with the optimal P content as the sensing material shows considerable performance for H2 detection at room temperature. The sensor exhibits an ultrahigh response of -921.9 μA to 15,000 ppm of H2. The sensitivity is -0.063 μA/ppm, which is 21 times higher than that of the conventional Pt/CF counterpart. The sensor also exhibits excellent repeatability and humidity resistance, as well as fast response/recovery; the response/recovery times are 31 and 4 s to 3000 ppm of H2, respectively. The modulation of the structure and catalytic properties of the support material is responsible for the improvement of the sensor performance, thus providing a feasible solution for optimizing the performance of fuel cell-type gas sensors.

Mixed Potential Type Acetone Sensor with Ultralow Detection Limit for Diabetic Ketosis Breath Analysis

Breath analysis using gas sensors is an emerging method for disease screening and diagnosis. Since it is closely related to the lipid metabolism and blood ketone concentration of the body, the detection of acetone content in exhaled breath is helpful for the screening and monitoring of diabetes and ketosis. The development of an acetone sensor with high selectivity, stability, and low detection limit has been the research focus for this purpose. Here, we developed a mixed potential type acetone sensor based on Gd2Zr2O7 solid electrolyte and CoSb2O6 sensing electrode. The developed sensor exhibits an extremely low detection limit of 10 ppb, enabling linear detection for acetone in an extremely wide range of 10 ppb-100 ppm. The good results of systematic evaluation on selectivity, repeatability, and stability prove the superior reliability of the sensor, which is a prerequisite for the application in actual breath detection. The ability of the sensor to distinguish healthy people from diabetic ketosis patients was confirmed by using the sensor to detect the breath of healthy people and diabetic patients, proving the feasibility of the sensor in the diagnosis and monitoring of diabetic ketosis.

A chemiresistive-potentiometric multivariate sensor for discriminative gas detection

Highly efficient gas sensors able to detect and identify hazardous gases are crucial for numerous applications. Array of conventional single-output sensors is currently limited by problems including drift, large size, and high cost. Here, we report a sensor with multiple chemiresistive and potentiometric outputs for discriminative gas detection. Such sensor is applicable to a wide range of semiconducting electrodes and solid electrolytes, which allows to tailor and optimize the sensing pattern by tuning the material combination and conditions. The sensor performance is boosted by equipping a mixed-conducting perovskite electrode with reverse potentiometric polarity. A conceptual sensor with dual sensitive electrodes achieves superior three-dimensional (sub)ppm sensing and discrimination of humidity and seven hazardous gases (2-Ethylhexanol, ethanol, acetone, toluene, ammonia, carbon monoxide, and nitrogen dioxide), and enables accurate and early warning of fire hazards. Our findings offer possibilities to design simple, compact, inexpensive, and highly efficient multivariate gas sensors.

High-Entropy Perovskites for Energy Conversion and Storage: Design, Synthesis, and Potential Applications

Perovskites have shown tremendous promise as functional materials for several energy conversion and storage technologies, including rechargeable batteries, (electro)catalysts, fuel cells, and solar cells. Due to their excellent operational stability and performance, high-entropy perovskites (HEPs) have emerged as a new type of perovskite framework. Herein, this work reviews the recent progress in the development of HEPs, including synthesis methods and applications. Effective strategies for the design of HEPs through atomistic computations are also surveyed. Finally, an outlook of this field provides guidance for the development of new and improved HEPs.

Electrochemical Response of Mixed Conducting Perovskite Enables Low-Cost High-Efficiency Hydrogen Sensing

High-performance noble metal-free gas sensors are crucial for widespread applications in various areas. Non-Nernstian electrochemical sensors have attracted tremendous attention, but are limited by the high cost and low efficiency of Pt electrode. Moreover, responses from different electrodes usually have the same polarity, degrading the sensor performance. Here we report a reverse response on a series of mixed ionic-electronic conductors (MIECs). Exemplary SrFe0.5Ti0.5O3-δ (SFT50) perovskite shows excellent H2 sensing properties, including high sensitivity and selectivity, humidity resistance, and long-term stability. Strikingly, the response is positive, as opposed to the usual one. Such an unusual response is ascribed to the change of the surface electrostatic potential due to the gas chemical reaction, which outcompetes traditional mechanisms, thereby reversing the response polarity. A conceptual noble-metal-free sensor with dual oxide electrodes of opposite polarity is designed by substituting SFT50 for the benchmark Pt, achieving a 1.5-2.0× increase in H2 response, sensitivity, and selectivity and a low limit of detection of 16 ppb. The ideal unity of excellent sensing and unusual polarity for MIECs can be used to optimize the performance of a variety of conventional sensors while reducing the cost. Our findings provide new insights into electrochemical gas sensing and offer a facile approach for developing low-cost high-performance gas sensors.

G. S, Suvina V, Sakar M, Balakrishna RG. Perovskite nanomaterials as optical and electrochemical sensors

The perovskite family is comprised of a great number of members because of the possible and flexible substitution of numerous ions in its system.

Pt/Graphene Catalyst and Tellurium Nanowire-Based Thermochemical Hydrogen (TCH) Sensor Operating at Room Temperature in Wet Air

We present a thermochemical hydrogen (TCH) gas sensor fabricated with Pt-decorated exfoliated graphene sheets and a tellurium nanowire-based thermoelectric (TNTE) layer operating at room temperature in wet air. The sensor device was able to detect 50 ppm to 3% of hydrogen gas within several seconds (response/recovery times of 6/5.1 s at 4000 ppm of hydrogen gas) at room temperature due to the relatively high surface area of homogeneously dispersed Pt nanocrystals (∼8 nm) decorated on graphene sheets and the excellent Seebeck coefficient (428 μV/K) of the TNTE layer. Furthermore, it was observed that the effect of the relative humidity on sensing properties was greatly minimized by incorporating Pt-decorated graphene sheets. These results indicate that our device has great potential as a low power consumption gas sensor for IoTs.

High Performance Mixed Potential Type NO2 Gas Sensor Based on Porous YSZ Layer Formed with Graphite Doping

High performance mixed potential type NO₂ sensors using porous yttria-stabilized zirconia (YSZ) layers doped with different concentration graphite as solid electrolyte and LaFeO₃ as sensing electrode were fabricated and characterized. LaFeO₃ was prepared by a typical citrate sol-gel method and characterized using XRD. The surface morphology and porosity of porous YSZ layers were characterized by field emission scanning electron microscope (FESEM). The sensor doped with 3 wt% graphite shows the highest response (-76.4 mV to 80 ppm NO₂) and the response is linearly dependent on the logarithm of NO₂ concentration in the range of 10-200 ppm. The sensor measurement results also present good repeatability and cross-sensitivity.

Enhancing resistive-type hydrogen gas sensing properties of cadmium oxide thin films by copper doping

The pure and Cu-doped CdO thin films with various doping concentrations (0.5 to 2 wt%) were deposited on amorphous glass substrates by a chemical spray pyrolysis technique for hydrogen gas sensor application.