Detection of volatile organic compounds by a catalytic combustion sensor under pulse heating operation

A catalytic combustion type gas sensor with low heat capacity employing Pd/gamma-Al2O3 was fabricated on a silicon substrate by micromachining and screen-printing. The sensor showed a large response peak before reaching a steady-state value upon pulse-heating for 0.2 s or 0.4 s with a cycle of 1-30 s when volatile organic compounds such as alcohol and acid were contained in the environment, while hydrogen and methane did not show such a response peak but a simple increase to a steady-state value. The peak height or area increased with increasing the non-heating period (0.6-29.6 s) and also with the concentration of target gases. The unique peak response has likely arisen from the combustion of the volatile organic molecules adsorbed on the catalytic sensor material during the non-heating period. The response mechanism was supported by temperature programmed desorption experiments of ethanol.