Highly sensitive H2 sensor based on PdO-decorated WO3 nanospindle p-n heterostructure

Abstract

A highly sensitive H2 gas sensor based on n-WO3/p-PdO heterostructure has been fabricated. Using hydrothermal method, through tuning the pH value of the solution, WO3 nanospindles were synthesized. SEM reveals its uniform morphology; XRD result shows its high crystal quality; N2 adsorption/desorption result proves its relatively high specific surface area. Through first soaking then calcinating method, PdO was loaded on the surface of WO3 nanospindles. XPS and HRTEM together have proved the fabrication of the heterostructure between n-WO3/p-PdO. The gas sensing device was fabricated by coating the PdO loaded WO3 paste on a ceramic substrate with silver palladium interdigital electrodes. After loaded into the test chamber, preheated to the required temperature and injecting a certain amount of H2, the sensing procedure was done. With optimal ratio of loaded PdO to WO3 (3 at%), the sensor shows the best gas sensitivity at 150 °C. To 1, 5, 10, 20 and 50 ppm H2, the sensor shows the response values (Ra/Rg) of 1.3, 7, 23, 37 and 76, in the response time of 9s, 8s, 5s, 3s and 1s, respectively. The quasi-one dimensional (QOD) character of WO3 nanospindle, the well-performance heterostructure between WO3 and PdO and the optimal ratio of loaded PdO to WO3 together make the sensor own strong sensing ability towards H2. The such well-performance H2 gas sensor based on n-WO3/p-PdO heterostructure reminds us that the WO3/PdO system has supplied a good material platform to explore the fabrication of ultrasensitive and stable H2 gas sensor.