Tungsten oxide, specifically WO3, possesses fascinating properties when interacting with hydrogen gas. This interaction underpins its significant role in hydrogen detection and sensing technologies. Tungsten oxide is a semiconductor material. When exposed to hydrogen gas at elevated temperatures, typically above 150°C, a remarkable change occurs. Hydrogen molecules dissociate on the oxide surface. The resulting hydrogen atoms inject electrons into the conduction band of the tungsten oxide. This process effectively reduces the oxide, forming tungsten bronze compounds like HxWO3. The most visually striking consequence is a dramatic color change. Pristine tungsten oxide is often pale yellow or transparent, but upon hydrogen exposure, it turns deep blue. This electrochromic effect provides a simple, visual indicator for hydrogen presence. Beyond color change, the electron donation significantly alters the material’s electrical resistance. Tungsten oxide exhibits a substantial decrease in electrical resistance upon hydrogen exposure. This measurable change forms the basis for highly sensitive chemiresistive hydrogen gas sensors. These sensors are crucial for safety in hydrogen fuel applications, leak detection in industrial settings, and various research environments. The sensitivity and selectivity of WO3-based sensors can be further enhanced through nanostructuring, doping with catalysts like platinum or palladium, or forming composites. While primarily valued for sensing, tungsten oxide’s interaction with hydrogen is also relevant in catalysis, particularly in hydrogenation reactions, and in advanced electrochromic devices for smart windows. Its ability to reliably and reversibly respond to hydrogen makes tungsten oxide a key functional material in the expanding hydrogen economy.

(tungsten oxide hydrogen)

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