Motional Resistance Evaluation of the Quartz Crystal Microbalance to Study the Formation of a Passive Layer in the Interfacial Region of a Copper|Diluted Sulfuric Solution.
A hyphenated technique based on vis–NIR spectroscopy and electrochemical quartz crystal microbalance with motional resistance monitoring was employed to investigate the dissolution of copper in acid media. Changes in motional resistance, current, mass, and absorbance during copper dissolution allow the evolution of the interfacial region of copper|diluted sulfuric solution to be understood. In particular, motional resistance is presented in this work as a useful tool to observe the evolution of the passive layer at the interface. During the forced copper electrodissolution in sulfuric solution, SO4(2–) favors the formation of soluble [Cu(H2O)6]2+. On the contrary, OH– involves the formation of Cu(H2O)4(OH)2, which precipitates on the electrode surface. The high viscosity and density of Cu(H2O)4(OH)2 formed on surface causes an increase in motional resistance independently of resonance frequency changes. During the copper corrosion in a more natural acidic environment, the results of electrochemical impedance spectra at open circuit potential indicate that corrosion is controlled by the diffusion of copper to the solution at short experimental times. However, copper diffusion is hindered by the formation of a passive layer on the electrode surface at long experimental times. During the copper corrosion, motional resistance shows an oscillatory response because of an oscillatory formation/dissolution of the passive later. Vis–NIR spectroscopy and electrochemical quartz crystal microbalance with motional resistance monitoring give new perspectives for reaching a deep understanding of metal corrosion processes and, in a future, other interfacial processes such as the catalysis or adsorption of (bio)molecules.
Department of Physical Chemistry, University of Valencia , C/Dr. Moliner, 50, 46100 Burjassot, Spain.
Alejandro
A
Cuenca
Department of Physical Chemistry, University of Valencia , C/Dr. Moliner, 50, 46100 Burjassot, Spain.
Jerónimo
J
Agrisuelas
Department of Physical Chemistry, University of Valencia , C/Dr. Moliner, 50, 46100 Burjassot, Spain.
Raquel
R
Catalán
Department of Physical Chemistry, University of Valencia , C/Dr. Moliner, 50, 46100 Burjassot, Spain.
José J
JJ
García-Jareño
Department of Physical Chemistry, University of Valencia , C/Dr. Moliner, 50, 46100 Burjassot, Spain.
Francisco
F
Vicente