Recent advancements in photoactivated metal oxide (MOX) gas sensors and the application of plasmonic nanoparticles (NPs) in hydrogen sensing have demonstrated significant potential in enhancing sensor performance. Hydrogen, as a high-energy, carbon-free alternative to fossil fuels, requires reliable detection methods due to its storage and handling risks. Traditional MOX gas sensors, while cost-effective and versatile, face challenges such as high operating temperatures and limited selectivity. In this review, innovative photonic methods are explored to overcome these limitations, focusing on photoactivation and plasmonic effects. Photonic activation improves sensitivity, response time, and recovery time at room temperature, mitigating the safety risks associated with high-temperature operations. Additionally, the integration of plasmonic NPs, made from gold, palladium, or other less noble metals, into MOX gas sensors enhances catalytic activity and sensor response through localized surface plasmon resonance. In this review, also the synergistic effects of noble metal decoration and photonic enhancement are covered, providing a comprehensive overview of the current state and possible future directions in hydrogen-sensing technology. These advancements promise safer and more efficient hydrogen detection, crucial for the expanding hydrogen infrastructure and its role in a sustainable energy future.
