Carbon monoxide detection at low temperatures by semiconductor sensor with nanostructured Au-doped CoOOH films

A series of cobalt oxyhydroxide (CoOOH) nano-films (250–450 nm thick) containing a small percentage of Au by mass were prepared from the component oxides through special precipitation and were sintered on the sensor substrate between Pt electrodes at 300 °C for 2 h. The sensor response to CO and other combustion by-product pollutants typical for early stages of fire, defined as Rg/Ra, where Rg and Ra denote the sensor electrical resistance in the sample gas and in air, respectively, was strongly promoted by addition of a small amount of Au to the CoOOH nanostructures. The results revealed that the sensors attached with Au-doped CoOOH sensing electrode (SE) have good sensitivity to CO in the temperature range of 60–110 °C with the maximum CO response near 80 °C. Cross-sensitivity investigation of these sensors to various gases has shown that the sensitivity of the nanostructured Au-loaded CoOOH-SE to CO is the highest among other gases. As the amount of Au loaded increased up to 0.5%, the device was found to be more sensitive to CO, whilst the addition of 1 mass% Au substantially degraded the sensing properties of the device. The promoting effects of Au were discussed based on the behaviour of electrical resistance of the Au-loaded sensors. The results of this work may be applicable to further development of carbon monoxide sensors for fire detection at its earlier stages.