Electrical & solid-state — overview

This section covers the electrical and solid-state sensor families — devices that turn a hydrogen-driven chemical or physical event into a resistance, voltage, current, or frequency you can read off a wire.

Pages, in reading order:

1. MOX chemiresistors — cheap-but-nonselective heated chemiresistors, the family in decades of household gas alarms.
2. Catalytic pellistors — combustion sensors for percent-level %LEL safety thresholds.
3. Palladium resistive & nanomaterial sensors — oxygen-independent devices that exploit Pd’s hydride chemistry.
4. Work-function devices — MIS/MIM/Schottky diodes and GasFETs reading the interfacial hydrogen dipole layer.
5. Thermal-conductivity & acoustic sensors — catalyst-free bulk-property detectors that read hydrogen’s outlier thermal conductivity and speed of sound.
6. 2D-material & nanostructure FET sensors — the frontier devices built on graphene, CNTs, MoS₂ and MXenes.

A recurring theme across all six pages: these are strong surface and safety instruments but mostly tuned for percent-level thresholds rather than the ppm-scale soil-gas anomalies exploration needs, and the field literature has largely converged on electrochemical cells for quantitative soil-gas H₂ work. For why trace H₂ detection is hard in the first place, start with why H₂ is hard.