New gas polarographic hydrogen sensor

Polarography is the measurement of the current that flows in solution as a function of an applied voltage. The actual form of the observed polarographic current depends upon the manner in which the voltage is applied and on the characteristics of the working electrode. The new gas polarographic H₂ sensor shows a current level increment with concentration of the gaseous H₂ similar to those relating to metal ions in liquid electrolytes in well-known polarography. This phenomenon is caused by the fact that the diffusion of the gaseous H₂ through a gas diffusion hole built in the sensor is a rate-determining step in the gaseous-hydrogen sensing mechanism. The diffusion hole artificially limits the diffusion of the gaseous H₂ toward the electrode located at the sensor cavity. This gas polarographic H₂ sensor is actually an electrochemical-pumping cell since the gaseous H₂ is in fact pumped via the electrochemical driving force generated between the electrodes. Gaseous H₂ enters the diffusion hole and reaches the first electrode (anode) located in the sensor cavity to be transformed into an H⁺ ions or protons; H⁺ ions pass through the electrolyte and reach the second electrode (cathode) to be reformed to gaseous H₂. Gas polarographic O₂ sensors are commercially available; a gas polarographic O₂ sensor was used to prove the feasibility of building a new gas polarographic H₂ sensor.