11:55 - 12:15 T-3 - Surfaces and Interfaces

pH dependence of Electron Transfer at a Graphene Monolayer electrode

Michel Wehrhold1, Tilmann J. Neubert1,2, Anur Yadav1, Rodrigo M. Iost1 and Kannan Balasubramanian1

1School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof, Institut für Chemie, Humboldt-Universität zu Berlin, Unter den Linden 6, 10117, Berlin, GER

2Institut für Silizium-Photovoltaik, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Kekuléstr. 5, 12489, Berlin, GER

The majority of graphene-based electrochemical sensors are realized on insulating materials, on one hand, to stabilize the one atom-thick electrode and on the other hand, to avoid a contribution from an underlying metal on the electrochemical response. 1 Here, we find that the kinetics as well as the reversibility of the reduction and oxidation of classical well-studied redox probes are dictated by the solution pH. 2 We attribute this phenomenon to specific, electrostatic interactions between the supported graphene monolayer and the redox probe itself. 3 Furthermore, we show that the choice of insulating substrate plays a crucial role on the electrochemical response. We see that the electrochemistry is dependent on the kind of substrate. 4 This behavior, which appears to be intrinsic to graphene, is attributed to different amounts of ionizable groups at the supported graphene-liquid-interface. 5 This finding will have a great impact in designing graphene-based electrochemical (bio-)sensors.

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The pH dependence of the electrochemistry of ferri-/ferrocyanide couple on supported monolayer graphene. By changing the solution pH from 2 to 7, the redox reversibility of the ferri-/ferrocyanide couple is lowered due to specific interactions between the redox probe and the supported graphene-liquid interface.

  1. L. Macedo, et al. ChemElectroChem, 6.1 (2019), 31-59

  2. M. R. Deakin, et al. J Electroanal Chem Interfacial Electrochem, 182 (1985), 113-122

  3. M. Wehrhold, et al. Nanoscale, 11 (2019), 14742-14756

  4. J. Hui, et al. Electrochimica Acta, 211 (2016), 1016-1023

  5. L. Zuccaro, et al. Scientific Reports, 5 (2015), 11794