In situ modification of discoid α-Fe2O3 nanostructures with Bi2WO6 for high performance n-butanol sensor

Intentionally constructing n-n or p-n heterojunctions in nanostructured metal oxide semiconductor (MOS) has been verified to be one of efficient strategies to develop MOS-based gas sensors with high performance. Here, we demonstrate an n-n α-Fe2O3–Bi2WO6 heterojunction strategy to boost the gas sensitivity of α-Fe2O3 towards n-butanol. To construct α-Fe2O3–Bi2WO6 heterojunction in α-Fe2O3, a novel discoid nanostructure (DNS) of α-Fe2O3 that assembled with crystalline nanoparticles with the size around 20 nm was first prepared via a solvothermal method. Then, evenly distributed Bi2WO6 nanoparticles were modified on the α-Fe2O3 DNSs via a simple hydrothermal method. The finally obtained Bi2WO6@α-Fe2O3 DNSs were about 60–90 nm in center thickness and 250–300 nm in diameter. When applied in gas sensor for detecting volatile organic compounds (VOCs), the Bi2WO6@α-Fe2O3 sensor, as compared with the bare α-Fe2O3 sensor, exhibited impressive enhancements in n-butanol sensing performance, including higher sensitivity (0.225/ppm vs 0.073/ppm for 10–100 ppm n-butanol), better selectivity (Sn-butanol/Sacetone: 15.2 vs 6.4) and faster response speed (8 s vs 10 s for 50 ppm n-butanol). These improvements were considered to benefit from the sensitization effects of Bi2WO6@α-Fe2O3 heterojunction, whose mechanism is discussed in detail.