D. Chartouni et al., IN-SITU STM INVESTIGATION OF METAL HYDRIDE ELECTRODES IN ALKALINE ELECTROLYTE DURING ELECTROCHEMICAL CYCLES, Journal of alloys and compounds, 261(1-2), 1997, pp. 273-275
For more than a decade metal hydride electrodes have been investigated
by ex situ methods. In situ STM (Scanning Tunnelling Microscopy) allo
ws investigation of single metal hydride grains during the charge and
discharge process in the electrolyte. The advantage of STM measurement
s is its manifold analysing feasibility, e.g. surface morphology, surf
ace conductivity and atomic forces with spatial resolution, and even s
ometimes atomic resolution. Samples of alloy grains pressed into a gol
d pellet and the polished surfaces of bulk alloys were investigated in
concentrated alkaline electrolyte (6 M KOH) by means of STM. The volu
me expansion between the metal and the hydride was measured on a singl
e grain in the electrolyte. This value of Delta V/V=14.9% is very clos
e to the value observed from X-ray diffraction measurements (15.4%). M
ultiphase samples show a very inhomogeneous surface conductivity. The
identification of the phases with different surface conductivities is
a key in understanding the hydrogen absorption mechanism in the electr
olyte. (C) 1997 Elsevier Science S.A.