CO₂-sensing properties and mechanism of nano-SnO₂ thick-film sensor

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• 作者：Dandan Wang¹Author Vitae ; Yanping Chen¹Author Vitae ; Zhongxing LiuAuthor Vitae ; Ling LiAuthor Vitae ; Changmin ShiAuthor Vitae ; Hongwei QinAuthor Vitae ; Jifan Hu ; ^{hu-jf@vip.163.com" class="auth_mail" title="E-mail the corresponding author} ; ^{hujf@sdu.edu.cn" class="auth_mail" title="E-mail the corresponding author}Author Vitae
• 关键词：Gas sensor ; CO2
• 刊名：Sensors & Actuators: B. Chemical
• 出版年：2016
• 出版时间：May 2016
• 年：2016
• 卷：227
• 期：Complete
• 页码：73-84
• 全文大小：5570 K

文摘

The sensing response S of SnO₂ thick-film sensor based on nano-powders annealed at 600 °C to 2000 ppm CO₂ at the operating temperature 240 °C can reach 1.24 for the background of wet air with 14% of room-temperature (23 °C) relative humidity (RH), which is much larger than the corresponding value (1.048) in dry air. With an increase of humidity from 14% to 66% RH, the sensing response of SnO₂ to low CO₂ concentrations such as 2000–4000 ppm initially increases, peaks at about 34% RH, and then decreases. CO₂-sensing response monotonically decreases with an increase of humidity at high CO₂ concentrations such as 6000 and 20,000 ppm. Density functional theory calculations show that CO₂ molecule cannot be adsorbed onto stoichiometric SnO₂ (1 1 0) surface or SnO₂ (1 1 0) surface pre-adsorbed by O₂⁻ and O⁻ in dry air. When CO₂ is introduced to SnO₂ surface in wet air, CO₂ reacts with O of pre-adsorbed OH⁻, bringing about the formation of carbonates containing (CO₃)²⁻ and the dissociation/movement of surface OH⁻ group, accompanying the releasing of electron from CO₂ to SnO₂ surface. The appropriate pre-adsorption of OH⁻ on SnO₂ (1 1 0) surface promotes the sensing response of CO₂.