Probe effects on concentration profiles in the diffusion layer: Computational modeling and near-surface pH measurements using microelectrodes

Autor(es)

Critelli, Renan A. J. ^[1] ; Bertotti, Mauro ^[1] ; Torresi, Roberto M. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, Av Prof Lineu Prestes 748, BR-05508000 Sao Paulo, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Electrochimica Acta; v. 292, p. 511-521, DEC 1 2018.
• Citações Web of Science: 0

Resumo

A finite-element method was applied to the problem of measuring near-surface concentration values with a probe placed in front of the electrochemical interface. Those probes, like pH-sensing microelectrodes, interfere with mass transport and unreliable results may be obtained due to the local distortions. A pure diffusion problem was solved for a one-component two-dimensional axisymmetric model, under Dirichlet and Neumann-type boundary conditions at the substrate surface. The generalized results may be used to estimate the effects of the sensor tip-substrate distance on local current density and surface concentrations, and on measurement accuracy in absence of homogeneous reactions. To account for the presence of homogeneous reactions, simulations were performed for specific system compositions, using the near-surface pH measurement in solutions containing a buffering agent as an example. An IrOx microelectrode was used for experimental measurements of near-surface pH carried out in solutions displaying different buffering capacities. The results were compared to simulations performed for a one-dimensional model with simplified electrode kinetics, but fully describing the kinetics of homogeneous reactions. It is shown that valuable information on the electrochemical processes may be extracted by using this experimental approach, even when the measured pH does not strictly correspond to the pH effectively experienced by the substrate surface. (C) 2018 Elsevier Ltd. All rights reserved. (AU)

• Processo FAPESP: 15/26308-7 - Otimização das propriedades físico-químicas de materiais nano-estruturados e suas aplicações em reconhecimento molecular, catálise e conversão/armazenamento de energia
• Beneficiário: Roberto Manuel Torresi
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 15/20776-9 - Fabricação de sondas com dimensões nanométricas para o estudo de processos bioquímicos usando Microscopia Eletroquímica
• Beneficiário: Mauro Bertotti
• Modalidade de apoio: Auxílio à Pesquisa - Regular