Adsorption/combustion-type VOC sensors employing mesoporous γ-alumina co-loaded with noble-metal and oxide

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• 作者：Takeo Hyodo^a ; ^{hyodo@nagasaki-u.ac.jp" class="auth_mail" title="E-mail the corresponding author}Author Vitae ; Takumi Hashimoto^aAuthor Vitae ; Taro Ueda^aAuthor Vitae ; Osamu Nakagoe^aAuthor Vitae ; Kai Kamada^aAuthor Vitae ; Takahiko Sasahara^bAuthor Vitae ; Shuji Tanabe^aAuthor Vitae ; Yasuhiro Shimizu^aAuthor Vitae
• 关键词：Adsorption/combustion-type gas sensor ; Platinum ; Alumina ; CeO2 ; VOC
• 刊名：Sensors & Actuators: B. Chemical
• 出版年：2015
• 出版时间：1 December 2015
• 年：2015
• 卷：220
• 期：Complete
• 页码：1091-1104
• 全文大小：3917 K

文摘

Mesoporous (mp-)Al₂O₃ powders, which were prepared by microwave-assisted solvothermal treatment of aluminum secondary butoxide in 1-propanol at 110 °C followed by firing at 700 °C in air, were loaded with l wt% MO (CeO₂, CuO, Fe₂O₃, Mn₂O₃, NiO or RuO₂, l ≤ 20 (wt%)) by impregnation with the constituent metal salt in the aqueous solution followed by firing at 700 °C in air. Thereafter the mp-Al₂O₃ powders loaded with and without MO were further co-loaded with noble metal nanoparticles, which were synthesized by sonochemical reduction. The VOC-sensing properties of the adsorption/combustion-type gas sensors fabricated by MEMS technology and drop coating technique utilizing the mN₁/nN₂/mp-Al₂O₃, 1.0Pt/mp-Al₂O₃ and 1.0Pt/lMO/mp-Al₂O₃ (N₁, N₂: Au, Pd and Pt, m and n: the amount of N₁ and N₂ nanoparticles loaded, m + n = 1.0 (wt%)) obtained as sensor materials were investigated in this study. The general ethanol response (ΔV_MAX) of all mAu/nPt/mp-Al₂O₃ sensors was smaller than that of the 0.2Au/0.8Pd/mp-Al₂O₃ sensor, which showed the largest ΔV_MAX among mAu/nPd/mp-Al₂O₃ sensors in our previous study. In the series of mPt/nPd/mp-Al₂O₃ sensors, on the other hand, the 0.8Pt/0.2Pd/mp-Al₂O₃ sensor showed larger ΔV_MAX to ethanol than that of the 0.2Au/0.8Pd/mp-Al₂O₃ sensor. Moreover, the ΔV_MAX of the Pt/mp-Al₂O₃ sensor to ethanol was slightly larger than of the 0.8Pt/0.2Pd/mp-Al₂O₃ sensor. The co-loading of 10 wt% MO with 1.0 wt% Pt nanoparticles onto the mp-Al₂O₃ was effective in improving the ΔV_MAX to ethanol of the Pt/mp-Al₂O₃ sensor in some cases, and the 1.0Pt/10CeO₂/mp-Al₂O₃ sensor showed the largest ΔV_MAX to ethanol among all the 1.0Pt/10MO/mp-Al₂O₃ sensors tested. The ΔV_MAX of the 1.0Pt/10CeO₂/mp-Al₂O₃ sensor to other VOCs (acetone, ethyl acetate, benzene, toluene and o-xylene) was relatively smaller than that to ethanol, but the shape of the differential sensor-signal profiles largely depended on the kind of VOCs and thus detailed analyses by the differential processing may have an advantage in the VOC-selective detection. On the other hand, integral processing of the sensor-signal profiles showed that the magnitude of the approximately integrated dynamic response (IDR), which was largely dependent on the amount of VOCs adsorbed on the mp-Al₂O₃, may provide an indication of the quantitative VOC detection. Furthermore, the control of the amount of CeO₂ loaded and the value of low temperature at pulse-driven heating enabled the 1.0Pt/lCeO₂/mp-Al₂O₃ sensors to detect a small amount of VOCs in comparison with general catalytic combustion-type gas sensors, because of the large IDR to the VOCs at a low-concentration range.