An electrochemically sharpened W tip was used as a spear to capture and manipulate single, quasi-spherical particles of metallic Zn a few tens of micrometers in diameter, harvested from the anode of a commercial Zn/MnO 2 battery. This tactic made it possible to acquire in situ Raman spectra of Zn passive films formed by potential step techniques on individual Zn microparticles in 1 M KOH aqueous solutions using a shallow electrochemical cell placed directly beneath the objective of the Raman microscope. The results obtained were in good agreement with those reported earlier for Zn disk electrodes, a few millimeters in diameter, in alkaline electrolytes using the same Raman instrument without a microscope. More specifically, films formed by stepping the potential from -1.55 V to either -0.7 or -0.8 V vs. SCE, displayed a largely enhanced feature at ca. 565 cm-1 ascribed to the E 1 longitudinal optical (LO) phonon modes of ZnO, an effect associated with the presence of intertial Zn and oxygen deficiencies in the lattice. In addition, significant amounts of crystalline ZnO could be detected only for passive films formed at the same two potentials after the electrodes had been microroughened by a single passivation-reduction step.
ASJC Scopus subject areas
- Materials Science(all)