NOVELTY - The hydrogen-sensitive composite material comprises a cerium-oxide composition chosen from cerium oxide, zirconium-doped ceria, gadolinium-doped ceria, samarium-doped ceria, lanthanum-doped ceria, yttrium-doped ceria, calcium-doped ceria, and strontium-doped ceria.    USE - Hydrogen-sensitive composite material is used for dual-element gas sensor devices and hydrogen-gas sensor devices (both claimed) used in fuel cell systems which are used as power supply for cars and domestic applications. The hydrogen-gas sensor device can also be used in residential or industrial applications, and for monitoring dangerous levels of hydrogen in air, housings of fuel-cell stacks, reformers, development test stands, and open locations, such as laboratories, refueling stations, and garages. The dual-element gas sensor device is used for detecting including but not limited to carbon monoxide, methane, hydrogen sulfide, sulfur oxide, nitrogen oxide, humidity, and ammonia.    ADVANTAGE - The composite material has excellent sensitivity to hydrogen. The material provides hydrogen sensor devices which provide quantifiable resistive responses, do not exhibit cross-sensitivities to interfering gases, such as carbon monoxide and methane, exhibit rapid response and recovery times, are capable of operating over a wide temperature range, exhibit stable performance over long time periods, have low power requirements, and are easily and economically manufactured.    DETAILED DESCRIPTION - The hydrogen-sensitive composite material comprises a cerium-oxide composition chosen from cerium oxide, zirconium-doped ceria, gadolinium-doped ceria, samarium-doped ceria, lanthanum-doped ceria, yttrium-doped ceria, calcium-doped ceria, and strontium-doped ceria. The composite material further comprises a noble promoter chosen from palladium, ruthenium, platinum, gold, rhodium and iridium. The composite material further comprises a modifier chosen from tin oxide, indium oxide, titanium oxide, copper oxide, cobalt oxide, tungsten oxide, molybdenum oxide, nickel oxide, iron oxide, niobium oxide, vanadium oxide, transition metal oxide(s), solid solution containing transition metal oxide(s), compound containing transition metal oxide(s), and mixture of two or more compounds each containing transition metal oxide(s). The content of cerium-oxide composition is 1-100 wt.%, the content of modifier is 0-99 wt.%, and the content of noble metal promoter is 0-99 wt.%. A hydrogen-gas sensor device is formed using a support, electrodes, and a sensor coating applied to the electroded surface of the support. The support is formed of aluminum oxide, yttria-stabilized zirconia, cerium oxide, gadolinium-doped ceria, magnesium aluminate, and/or magnesium oxide.