Detection of hydrogen permeation through pure iron with light-addressable potentiometric sensor

A light-addressable potentiometric sensor (LAPS) is a semiconductor-based chemical sensor, in which the measurement area is defined by a probe light illuminating the sensor plate. In this study, a novel method to detect hydrogen permeation through metal was proposed using a measurement system, in which a LAPS was combined with a micro-volume measurement cell. The sensing surface of the LAPS was placed in the vicinity of the hydrogen exit surface of an iron sheet to form the micro-volume cell. The cell was filled with a Na₂HPO₄ solution, and then the pH change of the solution due to production of protons during the electrochemical hydrogen permeation was detected. After loading hydrogen atoms from the hydrogen entry side into the iron sheet, the photocurrent – bias voltage characteristics of the LAPS showed a shift indicating production of protons. The result suggested the possibility of applying the LAPS to visualization of hydrogen permeation sites on the metal surface.