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Overcoming the intrinsically inferior chemiresistive sensing properties of ABO 3 perovskites remains a long-standing challenge. Herein, the in-situ derived ABO 3 -based heterostructures is proposed as promising sensitive materials for achieving high-performance chemiresistive sensing application. For verifying the feasibility, we design mesoporous p-p heterostructures composites of La 2 O 3 /LaFeO 3. In virtue of the formation of in-situ derived p-p heterojunctions, realizing the tailoring of charge carrier concentrations and energy band structure. Besides, the presence of La 2 O 3 with highly catalytic activity is helpful for improving gas sensing reactivity, and can generate large amount of lattice oxygen defects. Accordingly, the mesoporous La 2 O 3 /LaFeO 3 -based gas sensor operating at 200 °C exhibits high sensitivity, fast response and recovery speed (9 s/15 s vs. 100 ppm), outstanding selectivity and low detection limit (500 ppb), whereas the acetone sensing characteristic of LaFeO 3 based sensor is comparatively poor. Our work provides a facile strategy to improve chemiresistive sensing performances of ABO 3 perovskites. • In-situ derived p-p heterostructures for boosting ABO 3 -based chemiresistors sensing properties. • The mesoporous La 2 O 3 /LaFeO 3 acetone sensor exhibits relatively low detection limit and fast-responding. • Tailoring charge carrier concentration and energy band structure via p-p heterojunction. • Improving sensing reaction by the presence of La 2 O 3 with high catalytic activity. [ABSTRACT FROM AUTHOR]

Although the construction of heterojunctions between two different oxides is an attractive strategy to improve the sensing performance of metal oxide semiconductor (MOS) based gas sensors, there are few research reports focus on constructing p-p heterojunctions. Here we presented the sensitive material of p-p heterojunctions CoWO 4 -Co 3 O 4 nanocomposites derived from off-stoichiometric cobalt tungstate which are prepared through facile hydrothermal method. Owing to the presence of p-p heterojunctions can modulate the hole accumulation layer, the control of nanoarchitecture is beneficial for gas adsorption/diffusion and surface sensing reaction, and the catalytic activity is effectively tuned. The CoWO 4 -Co 3 O 4 based gas sensor showed higher response to xylene in ppb-level (300 ppb) at 200 °C, and negligible cross-responses to interfering gases such as ethanol (S xylene /S ethanol = 6.6), and has the capacity of long-term stability and strong anti-humidity. The gas sensing characteristics are greater than those of previously reported cobalt tungstate based gas sensor. Accordingly, this work provides a new perspective of preparing high-performance gas sensor based on p-p heterojunctions composites. • The p-p heterojunctions CoWO 4 -Co 3 O 4 nanocomposites were firstly used as sensitive materials for detecting xylene. • The off-stoichiometric cobalt tungstate were prepared through a facile hydrothermal route. • The CoWO 4 -Co 3 O 4 sensor with the ability of anti-humidity can exhibit superior sensing properties to ppb level of xylene. • The enhanced sensing mechanism of the p-p heterojunctions nanocomposites based gas sensor was reasonably proposed. [ABSTRACT FROM AUTHOR]

Trace detection and early warning of H 2 leakage at high temperatures were of great significance for eliminating safety hazards and ensuring the safety of human lives and property. In this paper, Ce 0.8 Gd 0.2 O 1.95 based mixed potential H 2 sensor were constructed using Ag@MO x (MO x = TiO 2 , In 2 O 3 , ZnO, V 2 O 5) as sensing electrodes synthesized by photochemical reduction method. Two sensing materials (Ag@TiO 2 and Ag@In 2 O 3) with excellent performance were selected by analyzing gas sensing properties of different sensing electrodes for H 2. Specifically, the detection range of the sensor with Ag@TiO 2 as the sensing electrode (operating temperature of 480 °C) was 1–10000 ppm, and the response to 200 ppm H 2 was −67 mV. The detection range of the sensor with Ag@In 2 O 3 (operating temperature of 490 °C) was up to the detection of 1–40000 ppm. The response value was −68 mV for 200 ppm H 2. The interaction between Ag and the oxide (synergistic hydrogen spillover effect), and the electron transfer behavior at the interface of Ag and oxide caused by the difference of work function were the main reasons for the sensitivity of sensors to H 2. This study contributed to an in-depth understanding for the influence of electronic behavior at the interface of noble metal and oxide on the sensing performance of solid electrolyte type gas sensor. Not only a new reference for subsequent researchers to construct high performance solid electrolyte type H 2 sensors was provided, but also a new choice for accurate and stable detection of H 2 over a wide concentration range at high temperatures was offered. • CeO 2 -based mixed potential sensor is designed for high temperature H 2 detection. • Ag is combined with TiO 2 , In 2 O 3 , ZnO and V 2 O 5 to compare their H 2 sensing properties. • Sensors using Ag@In 2 O 3 and Ag@TiO 2 as sensing electrodes exhibit good H 2 sensitivity. • Electron transfer at the Ag-oxide interface affects H 2 sensing performance. • Ag@In 2 O 3 sensor shows wide detection range (1–40000 ppm) and good humidity stability. [ABSTRACT FROM AUTHOR]

Trace detection and early warning of H 2 leakage at high temperatures are of great significance in eliminating potential safety risks and ensuring the safety of human life and property. Herein, Ce 0.8 Gd 0.2 O 1.95 -based mixed potential high temperature H 2 sensors made of AgRu@WO 3 synthesized by photochemical reduction method as the sensing materials are designed and demonstrated. By adjusting the content of Ag in WO 3 and the ratio of Ag and Ru, the sensitivity of the sensor is effectively improved and the operating temperature is reduced. The interaction between Ag and WO 3 (synergistic hydrogen spillover effect) is the major reason for the sensitivity of sensors to H 2. Ru is further introduced with the aim of using its catalytic and dissociative capabilities to make the optimal operating temperature of the sensor well below the deflagration point of H 2 (520 °C for Ag@WO 3 to 430 °C for AgRu@WO 3). At 430 °C, H 2 in the range of 2–2000 ppm can be detected by such sensors. The response value to 50 ppm H 2 can reach − 79 mV. Analysis using X-Ray Diffractometer (XRD), Scanning Electron Microscope (SEM) and X-ray Photoelectron Spectroscopy (XPS) are performed to explore the formations of AgRu@WO 3 and its sensing mechanism. To the best of our knowledge, there are no reports on the use of bimetallic-modified metal oxide sensing materials for Ce 0.8 Gd 0.2 O 1.95 solid electrolyte sensors in order to simultaneously increase the sensitivity and reduce the operating temperature. This study provides a new reference for subsequent researchers in the selection of sensing materials for solid electrolyte sensors, as well as a new option for accurate and stable detection of H 2 at high temperatures. • Ce 0.8 Gd 0.2 O 1.95 -based mixed potential sensor is designed for H 2 detection under high temperature. • Response to 50 ppm H 2 is increased to -79 mV which is attributed to the hydrogen spillover effect between Ag and WO 3. • Operating temperature is reduced from 520°C to 430°C which is attributed to the catalytic and dissociation ability of Ru. • The sensor shows wide detection range (2-2000 ppm), good selectivity and resistance to humidity. • The sensor provides a new option for accurate and stable detection of H 2 at high temperatures. [ABSTRACT FROM AUTHOR]