Defect-original room-temperature hydrogen sensing of MoO3 nanoribbon: Experimental and theoretical studies

Abstract

Rapid development in the hydrogen energy sector inspires improvement in the sensing properties of low-temperature hydrogen sensors. Both effective experimental researches and simulated calculations are highly beneficial in understanding the sensing mechanism of metal-oxide hydrogen sensors and enhancing their sensing capabilities. In this work, we prepare ultra-long orthorhombic MoO3 nanoribbons using a hydrothermal method. Hydrogen sensors based on single MoO3 are assembled under an optical microscope through a simple process. The concentration of Mo5+ in the nanoribbons can be adjusted by annealing in different atmospheres. The nanoribbon annealed in H2 atmosphere with Mo5+ concentration of ∼25% presents a higher sensor response of 11.23 towards 1000 ppm H2 than those annealed in a vacuum or an O2 atmosphere. Our gas-sensing testing results for different background atmospheres reveal that the oxygen species are closely related to the hydrogen sensing performance. The calculated researches show that pure hydrogen molecules cannot be adsorbed on MoO3 (010) surfaces both with and without defects. Oxygen molecules can capture the electrons from the MoO3 material to form chemisorbed species on the MoO3 (010) surface with terminal oxygen vacancies. The injected H2 gas can react with the pre-adsorbed O2− to form H2O, releasing electrons back to the sensing material. Our theoretical results are in good agreement with those of the experimental investigation.