Understanding on the hydrogen detection of plasma sprayed tin oxide/tungsten oxide (SnO2/WO3) sensor

Abstract

The plasma spray technique was well proven in producing metal oxide based gas sensors in the last two decades using different powder feedstocks. However, limited research was made to fabricate hydrogen gas sensor from tin oxide layer coated over tungsten oxide layer. This paper attempts to interpret the hydrogen gas sensing performances of plasma sprayed coating derived by depositing tin oxide layer over tungsten oxide (SnO2/WO3) layer. Plasma sprayed SnO2/WO3 sensor showed maximum response of 90% at 150 °C in contrast to stand-alone WO3 (89% at 350 °C) and stand-alone SnO2 (89% at 250 °C). The lower operating temperature of SnO2/WO3 sensor without compromising gas response was attributed to the WO3–SnO2 hetero-junction. SnO2/WO3 sensor showed selective sensing towards hydrogen with respect to carbon monoxide and methane gases. This sensor also possessed repeatable characteristics after 39 days from the initial measurement. In a nut-shell, plasma spayed SnO2/WO3 sensor showed stability of base resistance, repeatability after successive response and recovery cycles, selective sensing towards 500 ppm H2 with significant magnitude of gas response of 90%, response time of 35 s and recovery time of 269 s at a temperature of 150 °C.