Surface resistance change during nickel hydroxide phase transformations

R. TUCCERI

JOURNAL OF ELECTROANALYTICAL CHEMISTRY - (Print)

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2017 vol. 792 p. 104 - 109

1572-6657

Nickel hydroxide undergoes profound structural transformations underprolonged potential cycling in alkaline solutions. In this work, gold filmelectrodes modified with different nickel hydroxide coverages were subjected tocontinuous potentiodynamic cycling in alkaline medium, while the simultaneousevolution of voltammetric and surface resistance records was monitored untilstable responses were obtained. A surface resistance (SR) increase proportionalto the nickel hydroxide coverage was observed at potential values more negativethan -0.3 V (vs. SCE), which was attributed to the deposition of nickeladatoms from the reduction of nickel hydroxide layers. This SR change wasanalysed on the basis of the electron scattering theory, considering thatnickel adatoms act as scatterers for the reflection of gold conductionelectrons. The nickel adatom layer produced from the reduction of the nickelhydroxide structure formed during the first voltammetric scan potential cycles(less than 40) exhibits a more specular reflection than that generated after alarger number of potential cycles (more than 140). As the specularity of alayer for electron scattering can be associated with scatterer compactness, thedistance between nickel atoms in the former nickel adatom structure is shorterthan that in the last one.