New gas polarographic hydrogen sensor

Abstract

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 H/sub 2/ sensor shows a current level increment with concentration of the gaseous H/sub 2/ 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 H/sub 2/ 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 H/sub 2/ toward the electrode located at the sensor cavity. This gas polarographic H/sub 2/ sensor is actually an electrochemical-pumping cell since the gaseous H/sub 2/ is in fact pumped via the electrochemical driving force generated between the electrodes. Gaseous H/sub 2/ enters the diffusion hole and reaches the first electrode (anode) located in the sensor cavity to be transformed into an H/sup +/ ions or protons; H/sup +/ ions pass through the electrolyte and reach the second electrode (cathode) to be reformed to gaseous H/sub 2/. Gas polarographic O/sub 2/ sensors are commercially available; a gas polarographic O/sub 2/ sensor was used to prove the feasibility of building a new gas polarographic H/sub 2/ sensor.