Methanol gas sensing using ultramicroelectrodes: Studies on sensing mechanism and its enhancement

Electrochemical detection of methanol vapor has been achieved using a highly sensitive small detector by an ultramicroelectrode-based electrochemical method. First, a peak current was observed by employing potential sweep voltammetry at a microring ring electrode. The current peak was confirmed to be that of the methanol vapor. Next, (i) the potential-sweep rate dependence of the peak current at the microring ring electrode, and (ii) the electrode-gap width dependence of the cyclic voltammogram at the microgap electrode were measured. Based on the results, the electrochemical-detection mechanism of vapor methanol has been proposed. Finally, an enhancement method for detecting methanol vapor was achieved by the proposed mechanism. Namely, using a Nafion®-membrane-coated dualmicroelectrode we succeeded in detecting the methanol vapor by approximately 200 times higher than that by the bare electrode at an applied voltage of 4 V.