Fig. 5 illustrates that the j–E curve of the freshly polished and
the previously (in acidic solution, for the sake of potentiometric
use) oxidized W rod, in 0.1 M KOH, display no significant mutual
difference, which additionally vanish upon potential cycling. This
confirms that a unique W disk electrode can be quickly and easily
prepared for both reliable and reproducible potentiometric or nonpotentiometric
measurements (direct RDE voltammetry of H2 evolution
or hydrodynamic amperometric measurements of OH ions)
using here described procedures. For potentiometric use, only a
simple anodic oxidation in acidic solution is needed. Although proposed
oxidation procedure for the preparation of W/WO3 pH sensor
is somewhat lengthy and takes up to 12 h, having in mind
low price of tungsten, it is clear that a couple of W disk electrodes
can fully cover needs of most laboratories for pH or H+/OH concentration
measurements.