Solid-state Electrochemical Hydrogen Sensor

Crystalline Zr(HPO4)2 . H2O was prepared by direct precipitation method and its conductivity measurements were carried out with varying temperature. The effects of temperature, variable H3PO4contents and relative humidity on the conductivity of Sb2O5-H2O-H3PO4 have been studied. Experiments results show that crystalline Zr(HPO4)2 . H2O and composite electrolyte Sb2O5-H2O-H3PO4 have high protonic conductivities at room temperature (about 10-4-10-3S cm-1) and are less sensitive to humidity, therefore the protonic electrolytes are highly promising materials for application in hydrogen sensor operating at ambient temperature.A potentiometric solid-state hydrogen sensor using these electrolytes has been developed with catalytic and reference electrodes which bonded by using mixed pressing technique and in-situ impregnation reduction chemical method. The sensor is composed of the following electrochemical cell:H2 ( in N2 or air ) , Pd | solid protonic electrolyte | Pd ( or Ag ), air The influences of temperature and hydrogen concentration on the response signal are examined. The working mechanism of sensor of this type is studied by obtaining cathodic and anodic polarizations. It is found that the sensor utilizes a mixed potential at the sensing electrode. Ag electrode is used as reference electrode, which is inert to H2, air flow is not necessary and therefore simplify the sensor structure.Activation energy of the reduction of oxygen are 57.56kJ/mol and 41.67kJ/mol in low and high current density. Reaction order are 0.97and 1.09.