Leak Detection and H 2 Sensor Development

Abstract

Low-cost, durable, and reliable Hydrogen safety sensor for vehicle, stationary, and infrastructure applications. A new zirconia, electrochemical-based sensor technology is being transitioned out of the laboratory and into an advanced testing phase for vehicular and stationary H 2 safety applications. Mixed potential sensors are a class of electrochemical devices that develop an open-circuit electromotive force due to the difference in the kinetics of the redox reactions of various gaseous species at each electrode/electrolyte/gas interface, referred to as the triple phase boundary (TPB). Therefore, these sensors have been considered for the sensing of various reducible or oxidizable gas species in the presence of oxygen. Based on this principle, a unique sensor design was developed by LANL and LLNL. The uniqueness of this sensor derives from minimizing heterogeneous catalysis (detrimental to sensor response) by avoiding gas diffusion through a catalytically active material and minimizing diffusion path to the TPB. Unlike the conventional design of these devices that use a dense solid electrolyte and porous thin film electrodes (similar to the current state-of-the-art zirconia-based sensors and fuel cells), the design of this sensor uses dense electrodes and porous electrolytes. Such a sensor design facilitates a stable and reproducible device response, since dense electrode morphologies are easy to reproduce and are significantly more stable than the conventional porous morphologies. Moreover, these sensors develop higher mixed potentials since the gas diffusion is through the less catalytically active electrolyte than the electrode. Lastly, the choice of electrodes is primarily based on their O2 reduction kinetics and catalytic properties vis-a-vis the target gas of interest.