The development of highly active, sensitive and durable gas sensing materials for the detection of volatile organic compounds (VOCs) is extremely desirable in 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-LDH) precursors at 300-400 ºC. 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 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 ºC. The ultrahigh sensing activity of theses Co3O4-TiO2 p-n heterojunctions originates from their hierarchical structure, high specific surface area (>120 m 2 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.

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