Mechanisms of Protonic Surface Transport in Porous Oxides: Example of YSZ

Stub, Sindre Østby; Vøllestad, Einar; Norby, Truls

doi:10.1021/acs.jpcc.7b03005

Cited by 82 publications

(114 citation statements)

References 51 publications

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“…Second, after chemical stabilization of the first layer, the water vapor is physically adsorbed onto the first chemisorbed layer (Figure S11b, Supporting Information). Upon coverage of the surface with water molecules, protons migrate through the medium along with hydronium ions (H 3 O + ), which is demonstrated by a vehicle mechanism . As the water molecule layer continuously forms on the surface, extra layers are developed on the first physisorbed layer, changing the physisorption from single to multilayer (Figure S11c, Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

Ionic‐Activated Chemiresistive Gas Sensors for Room‐Temperature Operation

Song

Shim

Suh

et al. 2019

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extensively studied because of their remarkable advantages including low cost, simple fabrication, high response, and easy integration with electronic circuits. To ensure high response and reversible operation of chemiresistive gas sensors, high operating temperatures of 150-400 °C are inevitably required for adsorption and desorption of target molecules on and off of the sensing materials. [3,4] However, this high temperature degrades the sensor stability and lifetime due to thermally induced grain growth, which can damage interconnected electronics. [5,6] Moreover, high power consumption (over ≈100 mW) is required, which must be decreased for the development of future battery-powered wireless sensors for applications to the IoT. [7] To design high performance gas sensors that operate at room temperature, a variety of approaches including self-heating, ultraviolet (UV)-assisted measurements, and 2D materials have been used for high stability and low power consumption. [8][9][10] Despite these extensive efforts, challenges remain including poor response and incomplete recovery because of the restricted modulation in electronic conductivity by insufficient reaction energy between the analytes and sensing materials. Recently, the utilization of humidity has been reported as an effective method for improving gas sensing performance at low temperatures.The development of high performance gas sensors that operate at room temperature has attracted considerable attention. Unfortunately, the conventional mechanism of chemiresistive sensors is restricted at room temperature by insufficient reaction energy with target molecules. Herein, novel strategy for room temperature gas sensors is reported using an ionic-activated sensing mechanism. The investigation reveals that a hydroxide layer is developed by the applied voltages on the SnO 2 surface in the presence of humidity, leading to increased electrical conductivity. Surprisingly, the experimental results indicate ideal sensing behavior at room temperature for NO 2 detection with sub-parts-per-trillion (132.3 ppt) detection and fast recovery (25.7 s) to 5 ppm NO 2 under humid conditions. The ionic-activated sensing mechanism is proposed as a cascade process involving the formation of ionic conduction, reaction with a target gas, and demonstrates the novelty of the approach. It is believed that the results presented will open new pathways as a promising method for room temperature gas sensors. Sensors/BiosensorsThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

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Section: Resultsmentioning

confidence: 99%

Ionic‐Activated Chemiresistive Gas Sensors for Room‐Temperature Operation

Song

Shim

Suh

et al. 2019

Small

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“…The hopping mechanism was predominant in this zone. The temperature dependence of the conductivity in this temperature range shows a strong negative activation energy, which can be ascribed to the strong dependence of the amount of absorbed water on temperature [44].…”

Section: Hopping Mechanismmentioning

confidence: 85%

“…The amount of water adsorbed on an oxide surface is described by Langmuir and BET theory which depends on the thermodynamics of the water adsorption reaction [42,43]. Norby et al [44] investigated the structure of an absorbed water layer on surfaces of yttria-stabilized zirconia (YSZ) as a function of temperature and humidity. At 30% relative humidity (RH), the water layer consisted of three monolayers; two chemisorbed water layers and one physiosorbed water that in combination displayed an ''ice-like'' structure [45].…”

Section: Proton Conduction At Low Temperaturementioning

confidence: 99%

Review: recent progress in low-temperature proton-conducting ceramics

et al. 2019

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Proton-conducting ceramics (PCCs) are of considerable interest for use in energy conversion and storage applications, electrochemical sensors, and separation membranes. PCCs that combine performance, efficiency, stability, and an ability to operate at low temperatures are particularly attractive. This review summarizes the recent progress made in the development of low-temperature protonconducting ceramics (LT-PCCs), which are defined as operating in the temperature range of 25-400°C. The structure of these ceramic materials, the characteristics of proton transport mechanisms, and the potential applications for LT-PCCs will be summarized with an emphasis on protonic conduction occurring at interfaces. Three temperature zones are defined in the LT-PCC operating regime based on the predominant proton transfer mechanism occurring in each zone. The variation in material properties, such as crystal structure, conductivity, microstructure, fabrication methods required to achieve the requisite grain size distribution, along with typical strategies pursued to enhance the proton conduction, is addressed. Finally, a perspective regarding applications of these materials to low-temperature solid oxide fuel cells, hydrogen separation membranes, and emerging areas in the nuclear industry including off-gas capture and isotopic separations is presented.

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“…Generally, the factors governing proton conductivity are regarded as the strength of the O-H stretching bond of the adsorbed H 2 O and the amount of H 2 O adsorbed on the surface. 15,25 From results of DRIFTS and TG measurements, it was presumed that enhancement of proton conductivity by Al doping was attributable to an increase of the adsorbed H 2 O amount, not to a change in the O-H stretching bond strength. Consequently, the Al doping effect to CeO 2 was identied as the increase of H 2 O amount over the catalyst surface, which contributes to the promotion of surface proton hopping.…”

Section: Discussionmentioning

confidence: 99%

“…In fact, both supports showed typical Arrhenius behavior: the conductivity decreased with decreasing temperature. In this temperature region (373 K < T < 673 K), the dominant conductive carrier mechanism was estimated as electron diffusion in the inner bulk, 15,25 because there is no surface adsorbate. Comparison of the behaviors of CeO 2 and Al-CeO 2 reveals that the apparent activation energy and the conductive magnitude were almost equal.…”

Section: Evaluation Of Proton Conductivitymentioning

confidence: 99%