Tuning Electrochemical Bistability by Surface Area Blocking in the Cathodic Deposition of Copper

Abstract

We report herein a precise control of the electrochemical bistability induced by surface area changes during the cathodic deposition of copper. Small additions of 1,10-phenanthroline (Phen) in the reaction media present an inhibiting effect on the global rate mainly due to the adsorption of protonated Phen. The increase of its concentration favors a shrinkage of the bifurcation (saddle-node) diagram and shifts it to less negative potentials. The dynamic instability is verified by impedance measurements, and a negative impedance is clearly found. We calculated the apparent molar mass of the adsorbents using in situ gravimetric monitoring in the electrochemical experiments, and the results indicate that mass changes occur mainly due to the reduction of copper from bivalent ions dissolved in the reaction media. Importantly, the adsorption of protonated Phen molecules does not show a considerable contribution in mass variations but prevents the formation of a copper course grained morphology over the surface. Imaging analysis indicates finer nodulations at the lower branch compared to the upper branch in the bistability domain. On the basis of these observations, a kinetic mechanism is proposed and a good agreement is obtained between the apparent molar mass extracted from experiments and the theoretical values. Altogether, our results contribute to a detailed physical chemical description of the nonlinear behavior, bringing new insights about this reaction and pointing out the possibility to design switchable surface electrodes by taking advantage of the bistable behavior.

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

“…As already observed, the corresponding suppression of the Hopf bifurcation diagram in electrocatalytic oscillators has been identified as a surface inhibition effect which corroborates with our experimental observations: a stronger inhibition noticed in the Cu­(II)–tartrate system induces compression in the oscillation domain, j vs pH. Likewise, a considerable shrinkage of the bistability region was observed as the irreversible surface poisoning evolved in the electrodeposition of Cu in acidic media . Such interpretation has not been considered in the oscillatory mechanism and, through our experiments, it might play a significant role in the description of the dynamic behavior.…”

“…Likewise, a considerable shrinkage of the bistability region was observed as the irreversible surface poisoning evolved in the electrodeposition of Cu in acidic media. 11 Such interpretation has not been considered in the oscillatory mechanism and, through our experiments, it might play a significant role in the description of the dynamic behavior. Figure 4 and Figure 5 display potential oscillations observed at several experimental conditions of pH and current density (detailed in the inlet of each graph) for the Cu(II)−lactate and Cu(II)−tartrate system, respectively.…”

“…The synthesis of materials with novel physicochemical properties employing the controlled manipulation of their microstructure at the atomic level became a field based on solid-state chemistry. , As recently proposed, nevertheless, self-organization under far from equilibrium conditions can also be utilized as a promising and alternative synthetic method to create more complex materials in terms of structure and composition. − Differently from a standard step-by-step synthesis procedure, self-organized electrochemical structures arise without any external control or template-based support . Nanostructured metallic multilayers, magnetic nanopatterning, switchable roughness surfaces, and porous nanoarrays are a few examples found through the use of this nonequilibrium synthetic method. Followed by the spontaneous assembly of the material constituents, temporal instabilities, such as excitability, multistability, and oscillations, are observed on the main variables that describe the system .…”

“…3−7 Differently from a standard step-by-step synthesis procedure, self-organized electrochemical structures arise without any external control or template-based support. 8 Nanostructured metallic multilayers, 9 magnetic nanopatterning, 10 switchable roughness surfaces, 11 and porous nanoarrays 12 are a few examples found through the use of this nonequilibrium synthetic method. Followed by the spontaneous assembly of the material constituents, temporal instabilities, such as excitability, multistability, and oscillations, are observed on the main variables that describe the system.…”