Highly sensitive and selective xylene sensor based on p-p heterojunctions composites derived from off-stoichiometric cobalt tungstate

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 CoWO4-Co3O4 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 CoWO4-Co3O4 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 (Sxylene/Sethanol = 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.