Influence of the Ligands in Cu(II) Complexes on the Oscillatory Electrodeposition of Cu/Cu2O

Author(s)

Pinto, Maria R. ^[1] ; Pereira, Guilherme B. ^[1] ; Queiroz, Adriana C. ^{[1, 2]} ; Nagao, Raphael ^{[1, 2]}

Affiliation

^[1] Univ Estadual Campinas, Inst Chem, BR-13083970 Campinas, SP - Brazil

^[2] Univ Estadual Campinas, Ctr Innovat New Energies, BR-13083970 Campinas, SP - Brazil

• Document type: Journal article
• Source: Journal of Physical Chemistry C; v. 124, n. 23, p. 12559-12568, JUN 11 2020.
• Web of Science Citations: 0

Abstract

Oscillatory electrodeposition reactions have been utilized to create nanostructured materials under the microscale and nanoscale. This alternative method of synthesis, when compared to the traditional step-by-step synthesis procedure, takes advantage of the self-organizing processes that do not require any external control or template-based support, resulting in materials with higher complexity in terms of structure and composition. Nanolayers made of Cu and semiconductor composites, such as Cu/Cu2O, can be finely tuned by controlling ordinary period-one oscillations in the cathodic deposition. As the reaction media is alkaline, a complexing agent is commonly added in the solution to prevent the precipitation of the copper ions as hydroxides. Lactate and tartrate molecules are two alpha-hydroxy carboxylate organic ligands extensively used for this aim. Although some studies have shown the electrochemical synthesis of Cu/Cu2O nanolayers, no grounded discussion about the influence of the chemical nature of the ligands on the oscillatory reaction has been investigated so far. Here, we provide a well-detailed and rigorous study of the effect of both ligands in the electrodeposition of Cu/Cu2O under galvanostatic control, accurately mapping differences in the oscillation period and amplitude. On the basis of recent advances on the understanding of the copper complex structures, we attributed a distorted tetrahedral structure with four monodentate lactate ligands linked to the Cu2+ central ion ({[}Cu(Lac)(4)](2-)) and a distorted square-planar coordination of the tartrate's deprotonated alkoxide groups, forming a chelate ({[}Cu(TartH(-2))(2)](6-), as the species that have a buffering effect on the oscillatory mechanism and, consequently, can control the extension of the oscillation period and amplitude. In this matter, the tartrate complex should have a higher buffering capacity to prolong the period and decrease the amplitude. More importantly, we unequivocally show that a surface blocking effect due to the adsorption reactions cannot be neglected in the mechanism description. The adsorption of the tartrate anions and its complexes has, also as an outcome, period enlargement and amplitude shrinkage, as compared to that of the lactate. Hence, both mechanisms seem to operate in the adjustment of the dynamic characteristics of the oscillatory electrodeposition of Cu/Cu2O. (AU)

• FAPESP's process: 19/08244-2 - Synthesis of nanowires for application in the reduction reaction of carbon dioxide
• Grantee: Maria Rodrigues Pinto
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 16/01817-9 - Design and control of self-organized electrochemical patterns
• Grantee: Raphael Nagao de Sousa
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 17/11986-5 - Generation and storage of New Energy: bringing technological development for the country
• Grantee: Ana Flávia Nogueira
• Support Opportunities: Research Grants - Research Centers in Engineering Program