Pd-doped reduced graphene oxide sensing films for H2 detection

Abstract

The detection of low levels of hydrogen is becoming of ever-greater importance due to its potential use as a green energy. Current methods of hydrogen detection are predominantly based around three core technologies, semi-conductive chemiresistive metal oxides, electrochemical and chemical field-effect transistors. Of these techniques, metal-oxide and electrochemical sensors suffer from cross-sensitivity to a range of interferrent gases, CO being the most critical. Field-effect techniques are far more selective, but have a high cost of manufacture due to their complex construct, thus there is a need for a low-cost and selective sensing technology that could be applied to mass production. Here, we report on the fabrication, electrical and chemical characterisation of a Pd-doped reduced graphene oxide chemiresistors. Sensors were produced by the spin coating of graphene oxide onto a silicon based gold electrode structure, the graphene oxide was reduced and then Pd sputter coated. Initial investigation showed that the sensors have a clear response to hydrogen with sensitivity down to 50 parts per million level. Cross-sensitivity tests indicated that these sensors did not respond to CO, ethanol and toluene. Thermal characterisation showed that an increase in temperature improves sensor response by a factor of three between 30°C and 75°C. The effect of humidity was also explored; here an increase in sensor response was achieved at higher humidity concentrations, with sensor operation up to 75°C. In addition, the effect of Pd and reduced graphene oxide layers was investigated to evaluate its significance as a function of sensor response. Here a thickness of 3nm of Pd and 2nm of reduced graphene oxide were shown to offer the highest sensitivity. Finally, Pd doped graphene sensors were tested for comparison purposes. Here the sensor response of these sensors was found to be higher, though the manufacture process is far more complex. Doped reduced graphene oxide chemisresistors offer considerable promise as a mass produced gas sensor due to its ease of manufacture, good chemical performance and low cross-sensitivity. This may make such sensors ideal for future hydrogen detection applications.