Eye-readable sensors for intuitive hydrogen monitoring

Hydrogen energy is a cornerstone of the future climate-neutral economy. Yet, as undetected leaks easily generate dangerous atmospheres, sensing systems must timely detect accumulated hydrogen to prevent ignitions and explosions. Eye-readable sensors (ERSs) displaying intuitive readouts promise to guarantee safe use and universal access to hydrogen-based technology. This review highlights the impact of reversible ERSs in hydrogen monitoring to contextualize their current and potential applicability. First, sensing mechanisms for gasochromic tungsten oxide films and switchable metal hydrides are critically overviewed. Then, pivotal strategies targeting real-time monitorization indoors and permanent leak recording outdoors are presented along with standard hydrogen leakage scenarios, elucidating opportunities for ERSs. Finally, important challenges and desirable user-friendly concepts are discussed with the purpose of narrowing the gap between this class of sensors and the forthcoming hydrogen society.