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Facile synthesis of mesoporous hierarchical Co₃O₄–TiO₂ p–n heterojunctions with greatly enhanced gas sensing performance
- Zhang, Jiajun, Tang, Pinggui, Liu, Tongyuan, Feng, Yongjun, Blackman, Chris, Li, Dianqing
- Journal of materials chemistry A 2017 v.5 no.21 pp. 10387-10397
- active sites, adsorption, air, cobalt, cobalt oxide, durability, hydroxides, nanocomposites, oxygen, porous media, surface area, temperature, titanium dioxide, toluene, volatile organic compounds, xylene
- The development of highly active, sensitive and durable gas sensing materials for the detection of volatile organic compounds (VOCs) is extremely desirable for gas sensors. Herein, a series of mesoporous hierarchical Co₃O₄–TiO₂ p–n heterojunctions have been prepared for the first time via the facile thermal conversion of hierarchical CoTi layered double hydroxides (CoTi-LDHs) precursors at 300–400 °C. The resulting Co₃O₄–TiO₂ nanocomposites showed superior sensing performance towards toluene and xylene in comparison with Co₃O₄ and TiO₂ at low temperature, and the sample with a Co/Ti molar ratio of 4 shows an optimal response (Rg/Rₐ = 113, Rg and Rₐ denote the sensor resistance in a target gas and in air, respectively) to 50 ppm xylene at 115 °C. The ultrahigh sensing activity of these Co₃O₄–TiO₂ p–n heterojunctions originates from their hierarchical structure, high specific surface area (>120 m² g⁻¹), and the formation of numerous p–n heterojunctions, which results in full exposure of active sites, easy adsorption of oxygen and target gases, and large modulation of resistance. Importantly, hierarchical Co₃O₄–TiO₂ heterojunctions possess advantages of simple preparation, structural stability, good selectivity and long-term durability. Therefore, this work provides a facile approach for the preparation of hierarchical Co₃O₄–TiO₂ p–n heterojunctions with excellent activity, sensitivity and durability, which can be used as a promising material for the development of high-performance gas sensors.