The charge transport process at gold electrodes modified by thick nickel hydroxide films. A study employing rotating disc electrode voltammetry in the presence of the Fe(CN)63-/4- redox couple

R. TUCCERI

JOURNAL OF ELECTROANALYTICAL CHEMISTRY

ELSEVIER

Lugar: Amsterdam; Año: 2016 vol. 782 p. 125 - 132

0022-0728

Rotating disc electrodevoltammetry (RDEV) was employed to study the transport properties of nickelhydroxide films electrochemically deposited on gold in the presence of theFe(CN)63-/4- redox couple. Gold electrodes coated withnickel hydroxide surface coverages within the range 0.7 nmol cm-2< GNi(OH)2 < 55 nmol cm-2 were obtained. Steady-state current vs.potential (I-E) dependences at different electrode rotation rates within therange 50 rpm?5000 rpm were recorded for each GNi(OH)2value. While the anodic limiting current at thedifferent nickel hydroxide surface coverages followed the Levich equation, thecathodic limiting current only responded to the Levich relationship within the GNi(OH)2 range comprised between 0.7 nmol cm-2 and 16 nmol cm-2.The cathodic limiting current at GNi(OH)2values higher than 25 nmol cm-2 respondedto a reactant membrane diffusion phenomenon within the nickel hydroxide film.The cathodic process for thick nickel hydroxide films was associated with thephysical diffusion of the Fe(CN)63- species across thefilm to be reduced at the gold surface. A diffusion constant for the Fe(CN)63-species dependent on the nickel surface coverage was obtained. Althoughthe Fe(CN)64- oxidation seemed to occur by a rapidelectron-transfer process, a limiting electron-transport rate was observed at GNi(OH)2 values higher than 40 nmol cm-2 and at high electroderotation