Tantalum‐Palladium: Hysteresis‐Free Optical Hydrogen Sensor Over 7 Orders of Magnitude in Pressure with Sub‐Second Response

Hydrogen detection in a reliable, fast, and cost‐effective manner is a prerequisite for the large‐scale implementation of hydrogen in a green economy. Thin film Ta 1− y Pd y is presented as an effective optical sensing material with extremely wide sensing ranges covering at least 7 orders of magnitude in hydrogen pressure. Nanoconfinement of the Ta 1− y Pd y layer suppresses the first‐order phase transitions present in bulk and ensures a sensing response free of any hysteresis. Unlike other sensing materials, Ta 1− y Pd y features the special property that the sensing range can be easily tuned by varying the Pd concentration without a reduction of the sensitivity of the sensing material. Combined with a suitable capping layer, sub‐second response times can be achieved even at room temperature, faster than any other known thin‐film hydrogen sensor.