Characterization of a novel gas sensor using sintered ceria nanoparticles for hydrogen detection in vacuum conditions

Detection of trace amounts of hydrogen in vacuum conditions is essential in reusable space transportation systems and for safety control in manned space exploration. We evaluated the H2 detection in vacuum conditions by a novel gas sensor using sintered ceria (cerium oxide) nanoparticles. The results show that sensor resistance depended on H2 and O2 partial pressure ratios at any pressure from 10−5 Pa to atmospheric pressure. We conclude that the ceria resistance does not depend on total pressure but on H2 and O2 adsorption. The increase in sensor resistance resulted from a decrease in oxygen vacancies dependent on the O2 storage of ceria at a high O2 partial pressure. On the other hand, H2 dissociated and formed a cluster with ceria oxygen atoms when the H2 partial pressure was higher than the O2 partial pressure. Sensor resistance markedly decreased in these conditions because Ce3+ with free electrons were generated. The sensor could also detect other reducing gases such as CH4 and C4H10. In summary, the proposed sensor can convert gas adsorption into an electrical signal even in vacuum conditions, and has the potential to be a highly durable device with high sensitivity.