Electrochemical — overview

This section covers electrochemical hydrogen sensors, which read H₂ by driving it through a charge-transfer reaction at a catalytic electrode.

Pages, in reading order:

1. Electrochemical cells — room-temperature, liquid- or polymer-electrolyte amperometric and potentiometric devices. Cheap, linear, and field-proven — the workhorse for soil-gas H₂ surveys, fast and inexpensive enough to deploy in numbers. Not usable downhole, and readings are easily distorted by drilling, humidity, and temperature artifacts that every reading must be interpreted against.
2. Solid-electrolyte & high-temperature sensors — swap the wet electrolyte for a dense ceramic ion conductor (yttria-stabilized zirconia or a proton-conducting perovskite) that survives 200–900 °C. Mature for combustion and process monitoring, but they leave Hestia’s 100–300 °C downhole window a currently unfilled technology gap.