Fabrication of porous WO3/SBA-15 composite NOx gas sensor with a high sensitivity

SBA-15 was chosen as the matrix to form WO3/SBA-15 composite by chemical deposition method. The surfaces of prepared SBA-15 matrix were modified using silane coupling agent (SBA-15-Si) to enhance its surface activity, and then the SBA-15-Si was covered with a layer of W film through the chemical deposition method, and WO3/SBA-15 was obtained by the following calcination. By this method, the WO3 was preferentially deposited on the pore surfaces of SBA-15. The WO3/SBA-15 material was structured with amorphous SBA-15 and n-type WO3, but it strangely showed a p-type semiconducting character. At room temperature, WO3/SBA-15 gas sensor had an excellent and stable gas sensitivity of 96.6% with the response time of 5 s towards 100 ppm NOx (mixed gas of NO and NO2). The outstanding gas sensing properties of WO3/SBA-15 composite was attributed to the large specific surface area, small grain size and lattice mismatch between WO3 and SBA-15 substrate, which made the WO3/SBA-15 composite had the more active sites and lattice defects.