Hydrogen sensor based on WO3 subnano-clusters and Pt co-loaded on ZrO2

Abstract Pt and WO 3 co-loaded ZrO 2 equipped with a pair of interdigital Au electrodes has been tested as a H 2 gas sensor. The resistance R estimated from the intersection of the semi-circle with the real axis in a complex-impedance plot was used as a sensing signal. H 2 addition in a gas decreased the resistance. Pt–WO 3 /ZrO 2 showed a higher response magnitude to H 2 than WO 3 /ZrO 2 and Pt/ZrO 2 . The sensor was found to respond consistently and rapidly to change in concentration of H 2 in the oxygen rich and moist gas mixture at 120–150 °C. The conductivity of the device varied almost linearly with the H 2 concentration from 0.25 to 1.25%. The rate constants ( k ) of Pt–WO 3 /ZrO 2 for the response and recovery transients were 10 and 53 times higher than those of Pt/WO 3 , respectively. The response magnitude of Pt–WO 3 /ZrO 2 to H 2 was not markedly affected by changing the water vapor concentration from 1.0 to 3.4% and O 2 concentration from 5 to 20%. The effect of WO 3 loading of the Pt–WO 3 /ZrO 2 -based sensor combined with STEM and UV–vis results indicates that subnano-sized polytungstate clusters on the zirconia surface play an important role in the conductivity increase by H 2 adsorption, which can be due to an increase in the number of acidic H δ + species on the polytungstate surface.