Hydrogen concentration sensor

A hydrogen concentration sensor, comprising:

• a plurality of electrically conductive plates;
• a hydrogen evolving electrode assembly in a first location between two of the plates, the hydrogen evolving electrode assembly being configured to generate hydrogen;
• a detection electrode assembly in a second location between two of the plates with at least one of the plates including at least one separator plate between the detection electrode assembly and the hydrogen evolving electrode assembly, the detection electrode assembly being configured to provide an indication of a concentration of hydrogen in a fluid of interest, wherein the detection electrode assembly includes two electrode layers and a matrix layer between the two electrode layers;
• an internal passage extending in a thickness direction through the at least one separator plate between a hydrogen evolving electrode of the hydrogen evolving electrode assembly and a reference electrode of the detection electrode assembly on opposite sides of the at least one separator plate, wherein the internal passage is configured to communicate hydrogen evolved from the hydrogen evolving electrode to the reference electrode;
• a device that detects a voltage across the detection electrode assembly, wherein the detected voltage indicates the concentration of hydrogen in the fluid of interest;
• and
• a plurality of isolating layers, a first one of the isolating layers being at the first location between two of the plates, the first isolating layer including a sealant that secures the two plates at the first location, which the first isolating layer is between, together and seals a perimeter around the hydrogen evolving electrode assembly, a second one of the isolating layers being at the second location between two of the plates, the second isolating layer including a sealant that secures the two plates at the second location, which the second isolating layer is between, together and seals a perimeter around the detection electrode assembly.