Zero drift suppression for PdNi nano-film hydrogen sensor by vacuum annealing

Abstract

Zero drift is one of the important factors affecting the accuracy of hydrogen sensor. To restrain the zero drift, the PdNi nano-film hydrogen sensors were vacuum annealed and effects of different vacuum annealing temperatures on the micro-structure, morphology and hydrogen sensing performances were explored in detail. The results show that with the annealing temperature increasing, the grains grow and the lattice constantly decreases. And the morphology of the surface grains changes from cone to sphere when the annealing temperature is more than 250 °C. Moreover, we provide a concept of EZD (effect of zero drift) to quantitative analysis of the effect of zero drift on hydrogen sensing performance. Repeatability tests reveal that annealing can inhibit EZD when the annealing temperature is more than 150 °C, which is attributed to defects of PdNi nano-film reducing and stability improving. However, increasing annealing temperature leads to the deterioration of sensing performances such as response (Rs), response time (trs) and recover time (trc), especially when the annealing temperature is more than 250 °C. Only annealing at 250 °C can decrease EZD availably and make the PdNi nano-film hydrogen sensor maintain a high Rs and short trs and trc. In addition, the sensor annealed at 250 °C is appropriate for detecting hydrogen with low concentration and the detection limit is low to 2 ppm.