A double perovskite LaFe1-xSnxO3 nanocomposite modified by Ag for fast and accurate methanol detection

doi:10.1016/j.materresbull.2020.111006

Materials Research Bulletin

Volume 132, December 2020, 111006

https://doi.org/10.1016/j.materresbull.2020.111006 Get rights and content

Highlights

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Based on Ag doped double perovskite LaFe_1-xSn_xO₃ nanocomposite gas sensing material is prepared and investigated.
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The methanol gas sensing property of the sample is advanced and the experimental findings are innovative.
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The response of the Ag-LFSO nanocomposite sensor (51.94) to 5 ppm methanol is 6 times that of the aFeO₃ sensor.
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The Ag-LFSO nanocomposite sensor possesses a very fast response and recovery time (6 s/10 s).

Abstract

Perovskite-based metal oxides are one of the most prospective materials for detection of toxic, harmful and explosive gases, but the low electron mobility and ionic conductivity poses challenges in fast and accurate methanol detection. Thus, in this paper, the Ag doped double perovskite LaFe_1-xSn_xO₃ (Ag-LFSO) nanocomposite was prepared via a sol-gel assisted microwave chemical synthesis, which played the dual roles of fast response and good selectivity to methanol detection. The response of Ag-LFSO sensor to 5 ppm methanol is 51.94 at 99 °C, which is approximately 6 times higher than that of the pure LaFeO₃ sensor. Moreover, the significant enhancement of response and selectivity to methanol gas can be explained by the compensate for the position of Sn⁴⁺ in place of Fe³⁺ induced change in the carrier concentration and oxygen adsorption for LaFeO₃. In addition, Ag-doping can catalyze surface reactions and introduce electron defects at the surface of materials, thereby effectively improving the electrical conductivity and oxygen adsorption characteristics of LFSO. All the results indicated that the double perovskite Ag-LFSO sensor is an ideal choice for detecting toxic and harmful gases in practical applications.

Graphical abstract

Introduction

Nowadays, the environmental pollution and industrial emissions become more and more prominent because of the rapid economic development demand. Methanol gas, one of the main polluting gases, is mainly emitted from inferior high-sulfur coal and coke oven gas, and also comes from biomass such as forest trees and organic waste, it is toxic and dangerous to human body [1]. Inhaling a certain amount of methanol gas can cause blurred vision, insomnia, breath stopping and severe hepatitis, moreover, emissions of high concentration of methanol from factories can cause explosions. Timely and accurate monitoring of methanol gas in air can efficiently overcome these hazards. Therefore, studying an accurate and effective method to detect methanol gas cannot be delayed. The current detection methods are mainly chromatography, electrochemical methods, spectrophotometric methods and oxide semiconductor gas sensors [[2], [3], [4]]. Among them, the oxide semiconductor gas sensor has been known as the best detection method owing to its low cost, compact structure, easy to operate and simple manufacturing process.

At present, various nanostructured metal oxide semiconductors (MOS) including ZnO [5], SnO₂ [6], Co₃O₄ [7], NiO [8], TiO₂ [9], In₂O₃ [10] and LaFeO₃ [11] have been studied on methanol gas sensors due to their unique characteristics. Among them, perovskite oxides LaFeO₃ have gained extensive research due to its stable wide bandgap energy (1.9–2.2 eV), rich oxygen active center, controllable structure, and good stability [12]. It is well known that the performance of gas sensors depends mainly on the identification of the reaction surface and conductivity of the sensing layer [13], extensive research has been focused on the control of material composition and structure in order to obtain an active surface and generate free electrons [14]. The introduction of high valence or noble metal element in the precursor material is seen to be a simple and rapid method to modify the LaFeO₃ nanomaterial to enhance the catalytic activity to oxygen and target gases on the surface of gas sensing materials [11]. The doping amount and distribution of high valence or noble metal element are critical parameters for enhancing selectivity and response of gas sensor [15], such as Thangadurai et al. demonstrated that double perovskite-type BaCa_0.33Nb_0.34Fe _0.33O_3-δ (Fe-BCN) exhibit fast response to CO₂ gas [16]. Manorama et al. reported the response to H₂S gas can be improved nearly 8 times via doping of Ni²⁺ into Sr₂FeMoO₆ nanoparticles [17]. These results show that the formation of double perovskite-type structure through aliovalent element doping is an efficient way to enhance the gas response of composite oxides. In various doping elements, silver (Ag, possessing good chemical stability) and selenium (Sn, a versatile metal) has drawn our attention. The detailed reasons are as follows: (1) Via Sn doping, perovskite-type structure is formed in LaFeO₃, (2) the carrier concentration is changed to compensate for the position of Sn⁴⁺ in place of Fe³⁺, (3) the Ag-doping can catalyze surface reactions and introduce electron defects on the surface of materials, thereby effectively improving the electrical conductivity and gas response of LaFe_1-xSn_xO₃. So, Ag-LaFe_1-xSn_xO₃ (Ag-LFSO) is considered a good methanol gas sensor.

In this paper, we prepared double perovskite Ag-LaFe_1-xSn_xO₃ nanocomposites (x = 0.10, 0.20, 0.25, 0.3, 0.4 and denoted as Ag-LFSOI, Ag-LFSOII, Ag-LFSOIII, Ag-LFSOIV and Ag-LFSOV) by a sol-gel assisted microwave chemical synthesis. Under the optimal Sn concentration (x = 0.25), the Ag-LaFe_0.75Sn_0.25O₃ displays fast response, low operating temperature (T_sensor), good stability and selectivity. Further studies show that the outstanding gas response of Ag-LFSO could be attributed to the improved electrical conductivity and oxygen adsorption characteristics of gas sensing materials.

Section snippets

Materials

The reagents required during the experiment included lanthanum nitrate hexahydrate (LaN₃O₉·6H₂O, ≥99.90 %), iron nitrate (Fe(NO₃)₃·9H₂O, ≥98.50 %), tin (II) chloride dihydrate (SnCl₂, ≥99.0 %), silver nitrate (AgNO₃, ≥99.8 %), methacrylic acid (CH₂:C(CH₃)COOH, ≥99.0 %), 2,2-azobis (isobutyronitrile) (C₈H₁₂N₄, ≥98.0 %), polyethylene glycol 2000 (HO(CH₂CH₂O)nH), citric acid (C₆H₈O₇·H₂O, ≥99.5 %) and methanol (CH₃OH, ≥99.5 %). All chemicals were purchased from Sigma Aldrich. These chemicals were

Structure and morphology characteristics

Fig. 2(a) shows the phase and crystal structure for the prepared Ag-LFSO nanocomposites, the main XRD peaks of LaFeO₃ (100), (110), (111), (200), (210), (211) and (220) crystal surfaces are in good agreement with the standard card of LaFeO₃ (JCPDS card no. 37-1493) [7,18,19], we discovered that the XRD peaks of Ag-LFSO shift to higher angles when Fe is replaced by Sn [8]. Since the amount of Ag is so small that it could not be detected, no other clutter peaks are found, indicating that no other

Conclusion

In summary, we have demonstrated a series of double perovskite Ag-LFSO nanocomposites as a prominent gas sensor for fast and accurate detection of methanol gas. The sensor using Ag-LFSOIII show not only prominent selectivity and long-term stability but also fast response/recovery at the optimum working temperature (99 °C). A significant improvement in the methanol response can be attributed to the compensate for the position of Sn⁴⁺ in place of Fe³⁺ induced change in oxygen adsorption and the

Declaration of Competing Interest

None.

Acknowledgments

This work was supported by the National Natural Science Foundation of China (no. 51562038), the key Project of Natural Science Foundation of Yunnan (2018FY001(-011)) and Yunnan basic applied research project (no. 2017FB086).

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¹: These authors contributed equally to this work.

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A double perovskite LaFe1-xSnxO3 nanocomposite modified by Ag for fast and accurate methanol detection

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Materials

Structure and morphology characteristics

Conclusion

Declaration of Competing Interest

Acknowledgments

Sens. Actuators B

Sens. Actuators B

Sens. Actuators B

Nanoscale Res. Lett.

Sens. Actuators, B

Sens. Actuators, B

Talanta

J. Eur. Ceram. Soc.

J. Alloys Compd.

Sens. Actuators, B

Sens. Actuators, B

J. Hazard. Mater.

J. Hazard. Mater.

Sens. Actuators, B

Sens. Actuators, B

Sens. Actuators, B

Ceram. Int.

Sens. Actuators, B

Sens. Actuators, B

Sens. Actuators, B

A high sensitivity gas sensor toward methanol using ZnO microrods: effect of operating temperature

J. Elector. Mater.

Nano-sensors: towards morphological control of gas sensing activity. SnO2, In2O3, ZnO and WO3 case studies

Nanoscale

Growth of monoclinic WO3 nanowire array for highly sensitive NO2 detection

J. Mater. Chem.

Ultrasensitive xylene gas sensor based on flower-like SnO2/Co3O4 nanorods composites prepared by facile two-step synthesis method

Nanotechnology

A double perovskite LaFe_1-xSn_xO₃ nanocomposite modified by Ag for fast and accurate methanol detection

Nano-sensors: towards morphological control of gas sensing activity. SnO₂, In₂O3, ZnO and WO3 case studies

Growth of monoclinic WO₃ nanowire array for highly sensitive NO₂ detection

Ultrasensitive xylene gas sensor based on flower-like SnO₂/Co₃O₄ nanorods composites prepared by facile two-step synthesis method