As hydrogen can make an important contribution in the energy transition, its detection is necessary for safe application. Optical hydrogen sensors are a promising alternative to conventional hydrogen sensors as they are smaller, less expensive and safer. These sensors show a change in optical transmission upon exposure to hydrogen, allowing the partial hydrogen pressure to be probed. The optical response and the structural properties of Pd capped TaRu thin films are studied. A sensing range of 7 orders of magnitude in partial hydrogen pressure is observed, with a significant change in optical transmission upon hydrogenation. Exposure to hydrogen results in a phase transition of the Pd capping layer, leading to the hysteresis in the optical response of the sensor. This phase transition can be suppressed by alloying the capping layer. A sub-second response time is observed for large hydrogen pressures, which can be improved significantly using an additional PTFE layer. Phase transitions of the TaRu layer are suppressed by the
nanoconfinement of the sensing layer, and a solid solution is formed. The sensing range of TaRu can tuned by alloying Ta with Ru, resulting in a shift of the sensing range to higher hydrogen pressures. Implementing the suggested improvements would result in a hydrogen sensor with a sub-second response time and a tuneable sensing range of 7 orders of magnitude free of any hysteresis, proving TaRu to be an effective material for hydrogen sensing.