Zn–Ta-based oxide as a hydrogen sensitive electrode material for zirconia-based electrochemical gas sensors

A sensitive and selective hydrogen (H2) sensor using an yttria-stabilized zirconia (YSZ) solid electrolyte and a Zn–Ta-based oxide as the sensing electrode (SE) was developed. ZnO and Ta2O5 powder were co-sintered to form different compounds, and the sensing performance of the YSZ-based sensors utilizing the resulting SE materials was examined. The addition of 84 wt.% Ta2O5 into ZnO brought about the highest response toward H2, when compared with other examined Zn–Ta-based oxide SE materials. The XRD analysis revealed that the addition of 84 wt.% Ta2O5 into ZnO, after sintering at 1200 °C, formed ZnTa2O6, which is believed to be a contributor to H2 sensitivity. The sensor using this SE material was found to be capable of generating sensitive responses toward H2, with relatively low responses toward other examined gases at an operating temperature of 500 °C, under humid conditions. The present sensor was also found to be capable of detecting H2 concentration as low as 20 ppm in atmospheric conditions. The response toward H2 was hardly affected by H2O vapor concentration within the examined range of 1.35–5 vol.%.