Study Of Formaldehyde Gas Sensor Based On Metal Oxide

With the improvement of our life, indoors decoration has become more and more universal. However formaldehyde releasing from the decorative material has became the main air pollution indoors and one study showed that the formaldehyde has the mightiness cancer-causing function. Therefore it is necessary to examine the air pollution indoors. We carried through a research about the formaldehyde gas sensor which can support a simple and rapid test to the room's air quality.In the process of study on SnO2 gas sensor, we use the method of chemical deposition to prepare the Sn(OH)4 crystal, then turn it into SnO2 by sintering at certain temperature. These basal materials are what we need in our experimen. It is possible to enhance the sensor, sensitivity and selectivity by doping some noble metal into Sn(OH)4 according to the literature, and through research we got a conclusion: the gas characteristics of Sn(OH)4 gas sensor doped some noble metal is better than those SnO2 gas sensors doped some noble metal, and the best condition is maintaining sintering temperature at 650℃an hour. In addition, we selected AgNO3,H2PtCl6,PdCl2,HAuCl4 and RhCl3 as doping, through all the facture steps as described above, we start to test their sensitivity, selectivity, stability, response and recovery characteristics. From test results, we know doping RhCl30.2wt% is the best one, its IH is 90mA, selectivity is good (better than chloroform,ethanol and toluene), it can test well at lower concentration of formaldehyde: 5×10-6, and sensitivity can reach above 3, response and recovery time are both within 60 seconds.As for the study of formaldehyde gas sensor based on ZnO, we prepare basic material ZnO by method of chemical deposition and XRD,SEM is used to character the structure and grain size of the resulting materials. Through aseries of tests, we confirm the doping percent of TiO2. Moreover in order to improve the sensor's performance further, we select RuO2,PdCL2 and RhCL3 as doping. And after testing their sensitivity, selectivity, response and recovery characteristics, element doped 10wt%TiO2 and 0.4wt% RuO2 stand out: its IH is 150mA, selectivity is good (better than chloroform and toluene), it can test well at lower concentration of formaldehyde (5×10-6), and sensitivity is 2.8, response and recovery time are 10s or so.Deeper job isn't carry on since the limited of time and experimental condition. The experiment should be improved in the future time. And the gas characteristics may continue to improve in the future. In a word, we basically succeed in making formaldehyde gas sensor and hope our research can pave the road for the deep research.