Widening the Range of Trackable Environmental and Health Pollutants for Li‐Garnet‐Based Sensors

Abstract

States, these contributors have led to an increased occurrence of natural disasters such as wild fires and hurricanes, which will continue to result in vast environmental climate-change-driven migration and resettling. As a consequence, disparities in terms of quality of life for humans will become much larger, demanding an affordable infrastructure that can locally measure changes in air pollution and minimize climate-change-induced socioeconomic conflicts. Shifts in the local temperature, humidity, and pollutant levels can lead to new diseases and their spread, which in turn requires a careful understanding and measurement of the interplay between these processes. With roughly 91% of the world's population living in urban areas breathing polluted air, [1] solid-state sensors at relatively low cost for the monitoring and control of environmental quality are imperative to preserve air quality, human health, and the environment. In this context, sulfur oxides, SO 2 and SO 3 , make up a sizeable portion of harmful pollutants, which are emitted from residential, manufacturing, and construction sectors through the combustion of sulfur-containing compounds in fossil fuels during oil and gas production and from natural processes such as volcanic eruptions and forest fires (Figure 1a). [4] Sulfur oxides may interact with the environment to cause toxicity, diseases, and environmental decay, playing a significant role in acid rain and having an adverse impact on forests, water, soil, corrosion, and human health (Figure 1b). [5][6][7][8] Moreover, considerable evidence indicates a link between SO 2 exposure and risk of missed abortion in the first trimester of pregnancy, alongside higher likelihood of stillbirth and birth defects due to maternal longterm exposure to pollutants. [9,10] The permissible exposure limit to SO 2 in the air and workplaces is 0.1-10 and 5 ppm, respectively, setting the upper limit for exposure without detrimental effects. [11,12] Conventionally, SO 2 concentrations are measured using one of two optical tracking technologies, IR spectroscopy, or UV absorbance spectroscopy, which are accurate and stable but rather expensive and dependent on bulky instruments (≈50 000 cm 3 ) and thus not suitable for real-time continuous monitoring required in miniaturized applications (Figure 1c). Alternative detection methods include gas chromatography and flame emission spectrometry, which are expensive, time consuming, and demand high power and are thus impractical for real-time monitoring and feedback control on a daily basis. [11,13] Classic chemical sensors integrated in phones, vehicles, and industrial plants monitor the levels of humidity or carbonaceous/oxygen species to track environmental changes. Current projections for the next two decades indicate the strong need to increase the ability of sensors to sense a wider range of chemicals for future electronics not only to continue monitoring environmental changes but also to ensure the health and safety of humans. To achieve this goal, more chemical sensing...

Design of triple and quadruple phase boundaries and chemistries for environmental SO2 electrochemical sensing

“…The solid electrolyte Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZO) was prepared via the solid-state reaction route detailed elsewhere. 13 In short, stoichiometric amounts of La(OH) 3 (Sigma Aldrich, 99.9%), ZrO 2 (Sigma Aldrich, 99.9%), and Ta 2 O 5 (Sigma Aldrich, 99.99%) and an excess amount of 50 wt% LiOH (Alfa Aesar, purity 99.8%) to compensate for the lithium evaporation during the high-temperature calcination of the powder were ball-milled in absolute isopropanol, dried, and calcined two times at 750 C for 10 h at a heating rate of 5 C min À1 under a constant ow of synthetic air. Finally, a weighed amount of the LLZO powder was pressed into a pellet using a die with a diameter of 12 mm and thickness of 1.5 mm in a uniaxial press (2.2 tons per cm 2 ).…”

“…The SO 2 gas sensing experiments were conducted using a Linkam stage (HFS600E) with an internal volume of $50 cm 3 equipped with a heating element in the temperature range of 25-600 C. The experimental set-up has been detailed elsewhere. 13 In short, two automated mass ow controllers (red-y, Vogtlin instruments, Switzerland) were used to balance between 50 ppm SO 2 (in dry synthetic air) and dry synthetic air (21% volume O 2 in N 2 ) to achieve different concentrations of the analyzed gas, namely 0-10 ppm SO 2 in 2.5 ppm steps, held for 1-2 h. The open-circuit voltage (OCV) was measured using a Keithley 2612B electrometer. The reference and auxiliary (sensing) electrodes were connected using Pt wires, which were glued to the electrodes with gold paste.…”

“…It has been shown that developments in solid-state batteries (SSBs) 10 have been strongly connected to the new discoveries of novel solid-state electrolyte and electrode candidates, 11,12 which have recently been slowly integrated in beyond-battery applications such as sensors and memristors. [13][14][15] Very recently, a rst proof-of-concept for a potentiometric type III SO 2 sensor (where the auxiliary sensing electrode contains both the gaseous SO 2 species and the Li + mobile carrier of the solid electrolyte) based on a Li 2 SO 4 -CaSO 4 -LLZO composite sensing electrode and Li 6.54 La 3.00 Zr 1.36 Ta 0.50 O 11.73 solid electrolyte was demonstrated, showing a close-totheoretical sensitivity of 47.7 mV dec À1 at a remarkably low operating temperature of the sensor of 240 C. 13 This work demonstrated the ability to widen the range to track more gas pollutants from CO 2 to SO 2 with a similar sensor geometry. 13,16 Nonetheless, the SO 2 sensing performance was shown to be limited with a long response time on the order of $30-40 min, which was attributed to the sluggish kinetics at the sensingelectrode interfaces and the rather dense microstructure of the sensing electrode.…”

“…[13][14][15] Very recently, a rst proof-of-concept for a potentiometric type III SO 2 sensor (where the auxiliary sensing electrode contains both the gaseous SO 2 species and the Li + mobile carrier of the solid electrolyte) based on a Li 2 SO 4 -CaSO 4 -LLZO composite sensing electrode and Li 6.54 La 3.00 Zr 1.36 Ta 0.50 O 11.73 solid electrolyte was demonstrated, showing a close-totheoretical sensitivity of 47.7 mV dec À1 at a remarkably low operating temperature of the sensor of 240 C. 13 This work demonstrated the ability to widen the range to track more gas pollutants from CO 2 to SO 2 with a similar sensor geometry. 13,16 Nonetheless, the SO 2 sensing performance was shown to be limited with a long response time on the order of $30-40 min, which was attributed to the sluggish kinetics at the sensingelectrode interfaces and the rather dense microstructure of the sensing electrode. As the sensing-electrode reaction primarily occurs at the ionic/electronic/gas junctions, it was evident that creating and making interconnected designs may be an interesting pathway for the future; however, this route has not yet been tackled.…”

Ultrathin 2D NbWO6 Perovskite Semiconductor Based Gas Sensors with Ultrahigh Selectivity under Low Working Temperature

“…[3] H 2 S is also used as an important endogenous gas signaling molecule for physiological regulatory in the cardiovascular, endocrine, and gastrointestinal, etc. [4] Therefore, the design of high-performance H 2 S sensors with high selectivity, [5] low working temperature, [6] high sensitivity, [7] fast response-recovery dynamics, [8] and long-term stability are highly essential in many fields of science and technology. [9] A number of examples have been reported for H 2 S sensors and related trapping engineering based on semiconducting metal oxides, such as, WO 3 , [10] Ga 2 O 3 , [11] SnO 2 , [12] ZnO, [13] and so on.…”