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In situ characterization of the oxygen reduction reaction on carbon based materials by Shell-isolated nanoparticle-enhanced Raman Spectroscopy

Grant number: 19/04484-9
Support type:Scholarships abroad - Research
Effective date (Start): September 12, 2019
Effective date (End): November 19, 2019
Field of knowledge:Physical Sciences and Mathematics - Chemistry
Principal Investigator:Ana Maria Gomez Marin
Grantee:Ana Maria Gomez Marin
Host: Laurence Hardwick
Home Institution: Divisão de Ciências Fundamentais (IEF). Instituto Tecnológico de Aeronáutica (ITA). Ministério da Defesa (Brasil). São José dos Campos , SP, Brazil
Local de pesquisa : University of Liverpool, England  

Abstract

Elucidating the mechanism of the oxygen reduction reaction (ORR), a fundamental process in fuel cells and metal-air batteries, is essential for a successful design of sustainable systems for energy conversion and storage. Despite more than 60 years of research, surface processes taking place during the ORR are non-well understood, being this an important bottleneck for massive commercialization of these devices, and one of the reasons for the marginal success in designing new and more active ORR catalysts than platinum, the most active pure metal known so far. Unfortunately, a detailed description of the phenomena governing these systems at a molecular level is still missing and experimental and theoretical investigations from manifold angles, especially by employing in-situ/operando techniques, are necessary.Over past decades, carbon materials, such as graphite, glassy carbon, graphene, have attracted lot of attention not only as individual, cost-effective, ORR catalysts or catalyst supports, but also for the development of electrochemical capacitors, due to their low cost, good conductivity, high mechanical and chemical stability, and high surface area. Carbon materials are the most common support for Pt nanoparticles (NPs), and main component of non-precious metal ORR electrocatalysts. However, it is rather challenging to ascribe changes in carbon's microstructure or surface chemical composition, to a specific modification in the overall electrode performance, essential information for a successful development of new materials and electrode architectures. Hence, elucidating the relationship between carbon's performance -chemical composition - structure is an essential step toward the design of affordable energy conversion/storage systems.One of the biggest key challenging issues for in-situ/operando vibrational spectroscopy at the interface is to increase the limits of detection to identify chemical changes in the proximity of an electrode, without distorting the electrochemical response. Spectroscopy applications based on surface plasmon resonance, such as surface-enhanced Raman scattering (SERS), and the derived shell-isolated NP methodology, SHINERS, attempt to solve this problem by the use of nanostructured materials for enhancing the spectroscopic signal. The application of these techniques confirmed the formation of adsorbed superoxide and hydroperoxyl radical as intermediate during the ORR in several surfaces in alkaline and acid, respectively, but there are still many open questions regarding molecular details of the reaction. This information is crucial for a comprehensive understanding of the ORR mechanism, which in turn might guide the development of new electrocatalysts for practical applications.In SHINERS, SERS-active NPs surrounded by a chemically inert dielectric shell, like Au@SiO2, are employed as amplifier elements and spread over a surface of any material and morphology. This flexibility make it a promising, advanced in-situ/operando methodology for assisting the characterization and design of electrochemical interfaces. Inside this framework, three main objectives are pursued with the realization of the proposed research stay: i) To characterize the electrochemical interface of pristine and electrochemically oxidized carbon materials, such as glassy carbon, during the ORR by SHINERS, as an attempt to elucidate at molecular scale the relationship between carbon's ORR activity -chemical composition - structure.ii) To acquire experimental skills on SHINERS for implementing this methodology in the Laboratory of Electrochemistry of the Department of Chemistry of the Aeronautics Institute of Technology.iii) To establish an international research collaboration with Prof. Dr. Laurence J. Hardwick, Director of the Stephenson Institute for Renewable Energy at University of Liverpool at UK, basis for future productive collaborations that can be typified in joint publications and student's exchange.