Hydrogen Biosensing: Prospects, Parallels, and Challenges

The implementation of hydrogen, as a renewable and clean energy source, has the potential to replace fossil fuels and to decarbonize hard-to-abate sectors, enabling sustainable development with a lower environmental footprint. At concentrations higher than 4 vol %, hydrogen is, however, highly flammable and real-time monitoring and detection are required to ensure safe operation during production, storage, transportation, and utilization of it. Hydrogen sensors shall, therefore, be both efficient and sensitive to operate across a wide range of concentrations and mixtures with other gases. Current commercial hydrogen sensors are primarily dependent on electrochemical, heat-conductance, or calorimetric technologies, being intrinsically developed from noble and expensive metals or complex setups. Portable hydrogen sensing technologies for personal protective equipment in remote and confined areas shall, however, require them to be selective and specific, light weight, and mobile, as well as self-regenerating and stable for the long-term. An emerging type of hydrogen sensor involves biosensing through biological pathways whereby hydrogenase is extracted from microbial communities and used for carrying out the reversible hydrogen oxidation reaction, allowing sensitivity down to 0.4 ppb in complex environments. Microbial communities innately use hydrogen for metabolic activities related to growth and energy synthesis. This review highlights the recent developments in hydrogen biosensing while presenting viable options for on-site and fast hydrogen detection, allowing timely action for mitigating risks related to hydrogen leakages and inflammation. Beyond discussing the mechanisms and materials used to generate hydrogen biosensors, a critical comparison with conventional hydrogen and other gaseous sensors is presented, highlighting the opportunities and remaining challenges in this field.