Spectroelectrochemical Detection of Water Dissociation in Bipolar Membranes.

The potentials at which water dissociation occurs in bipolar membranes (BPM) and the relationship between water dissociation and current-voltage curve characteristics are explored using a novel spectroelectrochemical approach in which an anion exchange membrane is doped with a pH indicator. Using this method, we visually detect a pH change in the BPM resulting from OH formed during the water dissociation reaction. The color change is measured with a UV/vis spectrometer, while electrochemical characterization of the BPM is performed simultaneously.

The dehydrogenation mechanism during the incubation period in nanocrystalline MgH.

The dehydrogenation mechanism during the incubation period in nanocrystalline MgH (low α: converted metal fraction and dα/dt) and the reasons for the occurrence of the incubation period at 320, 350, and 400 °C were investigated. Pre-existing Mg crystallites can enhance Mg nucleation during the incubation period, as suggested by the estimated activation energy for nucleation (12 ± 2 kJ per mol H). The released H-atoms enter MgH as interstitials, as indicated by the MgH unit-cell contraction, resulting in increased equatorial Mg-H bond length, decreased charge-density distribution in the interstitial region, as observed from the charge-density maps, and decreased H-H distance in the {001} plane up to the midway of the incubation period.