Abstract
Cobalt oxides (CoOx) of different oxidation states were prepared from Co(NO3)2 solution through a precipitation with NaOH and oxidation by air. The prepared samples were characterized with techniques of X-ray diffraction (XRD), temperature-programmed reduction (TPR), thermal analysis (TG) and electron microscopy. Furthermore, we applied CoOOH for sensing materials of SCS CO sensors.From experimental results, we can find that : The oxidation state of cobalt oxides(CoOX) can be controlled by pH value . Co3O4 was the main product at pH < 9. CoOOH dominated at 9 < pH < 14, but the product became Co3O4 and Co(OH)2 at pH > 14.In SCS, the optimum working temperature of CO detection was about 80 oC (S = 5.6). The response time SCS based on CoOOH was short (~1 min). CoOOH has better sensitivity than Co3O4 and can detect low CO down to 1 ppm(S/N＝12). CoOOH has a high selectivity of CO relative to H2(Sco/SH2~4). The optimum working temperature(~80 oC) of CoOOH is lower than other semiconductor oxides on reviews.