Current atomic-level understanding of electrochemical nucleation and growth on low-energy surfaces

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Electrodeposition of nanostructured catalysts for electrochemical energy conversion: Current trends and innovative strategies

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New Insights in Nano-electrodeposition: An Electrochemical Aggregative Growth Mechanism

textcopyright Springer International Publishing Switzerland 2016. Supported nanostructures represent the cornerstone for numerous applications in different fields such as electrocatalysis (fuel cells) or electroanalysis (sensors). In contrast to other methods, electrochemical deposition allows the growth of the nanostructures directly on the final support, improving the electron pathway within the substrate, nanostructure, and electrolyte. However, despite the increasing number of publications in the field, the early stages of electrochemical nanocrystal formation are still under discussion. In this chapter, we first provide a survey on the traditional approaches to study the early stages of electrochemical nucleation and growth, together with the classical theories used to understand them. Next, we describe our most recent findings which have led to reformulate the Volmer-Weber island growth mechanism into an electrochemical aggregative growth mechanism which mimics the atomistic processes of the early stages of thin-film growth by considering nanoclusters of few nm as building blocks instead of single atoms. We prove that the early stages of nanoelectrodeposition are strongly affected by nanocluster selflimiting growth, surface diffusion, aggregation, and coalescence.info:eu-repo/semantics/publishe

Transition between kinetic and diffusion control during the initial stages of electrochemical growth using numerical modelling

Understanding properly electrochemical nucleation and growth phenomena is crucial for a wide range of highly active research and technological fields. In this paper, we use a Finite Element Method to solve a Time Dependent Multi-ion Transport and Reaction Model (FEM-TD-MITReM) to report on the growth of an isolated nucleus. This approach takes into account the transport driven by diffusion and migration of all species in the electrolyte together with the electrochemical reactions at the electrode boundary. The numerical results show that, a nucleus which is smaller than a critical size, even after the application of a sufficiently large overpotential, always starts to grow under kinetic control. In later stages, a transition from kinetic to mixed and to diffusion control takes place. The corresponding transition times between growth regimes have been identified and are found to be inversely proportional to the concentration of active species and to decrease exponentially with overpotential and linearly with the initial nucleus size. Both effects are more pronounced in the transition from kinetic to mixed control. Interestingly, under the conditions used for the current simulations, typical from experimental nucleation and growth studies, a few seconds are needed to achieve diffusion control. This implies that, although experiments under similar conditions are normally described by growth under diffusion control, such theory is only valid for sufficiently large active surface. As a consequence, kinetic and mixed control regimes cannot be neglected for a proper interpretation of electrochemical nucleation and growth phenomena. These findings provide a significant benchmark for correctly describing, modelling and interpreting the early stages of electrochemical growth without making assumptions on the diffusional or kinetic limitations.info:eu-repo/semantics/publishe

Carbon/PP composites and carbon/self-reinforced PP composites

Carbon/PP and carbon/self-reinforced PP hybrid composites have been produced by film-stacking. Tensile tests in carbon/PP composites show that the E-modulus is 15% lower than expected. Compared to carbon/PP materials, hybrid composites show an increase of 6-20% in ultimate strain and 10-15% in strength, while the E-modulus is kept as predicted.info:eu-repo/semantics/publishe

Impact and oxidation of single silver nanoparticles at electrode surfaces: one shot versus multiple events

High bandwidth-low noise measurements of the electrochemical oxidation of individual silver nanoparticles (NPs) impacting on electrodes reveals the process to typically occur in a series of ‘bites' (partial NP dissolution) rather than in a single shot, with the resulting current–time traces revealing considerable information on NP activity and transport near electrodes.info:eu-repo/semantics/publishe

Electrodeposition of Ag nanoparticles onto carbon coated TEM grids: A direct approach to study early stages of nucleation

An innovative experimental approach to study the electrodeposition of small nanoparticles and the early stages of electrochemical nucleation and growth is presented. Carbon coated gold TEM grids are used as substrates for the electrodeposition of silver nanoparticles so that electrochemical data, FESEM, HAADF-STEM and HRTEM data can be acquired from the same sample without the need to remove the particles from the substrate. It is shown that the real distribution of nanoparticles cannot be resolved by FESEM whereas HAADF-STEM analysis confirms that a distribution of 'small' nanoparticles (dinfo:eu-repo/semantics/publishe

New Insights into the Early Stages of Nanoparticle Electrodeposition

Electrodeposition is an increasingly important method to synthesize supported nanoparticles, yet the early stages of electrochemical nanoparticle formation are not per- fectly understood. In this paper, the early stages of silver nanoparticle electrodeposition on carbon substrates have been studied by aberration-corrected TEM, using carbon-coated TEM grids as electrochemical electrodes. In this manner we have access to as-deposited nanoparticle size distribution and structural characterization at the atomic scale combined with electrochemical measurements, which represents a break- through in a full understanding of the nanoparticle electro- deposition mechanisms. Whereas classical models, based upon characterization at the nanoscale, assume that electrochemical growth is only driven by direct attachment, the results reported hereafter indicate that early nanoparticle growth ismostly driven by nanocluster surfacemovement and aggregation. Hence, we conclude that electrochemical nulceation and growth models should be revised and that an electrochemical aggregative growth mechanism should be considered in the early stages of nanoparticle electrodeposition.info:eu-repo/semantics/publishe

Investigation of the Ordering of Porous Anodic Alumina Formed by Anodization of Aluminum in Selenic Acid

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Interply hybrid composites with carbon fiber reinforced polypropylene and self-reinforced polypropylene

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