Fabrication of porous WO₃/SBA-15 composite NO_x 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 NO_x (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.