Carbon nanodots: a new precursor to achieve reactive nanoporous HOPG surfaces
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Carbon nanodots: a new precursor to achieve reactive nanoporous HOPG surfaces Cristina Gutiérrez-Sánchez1 (), Emiliano Martínez-Periñán1, Carlos Busó-Rogero3, Mónica Revenga-Parra1,2,3, Félix Pariente1,2, and Encarnación Lorenzo1,2,3 () 1
Departamento de Química Analítica y Análisis Instrumental, Universidad Autónoma de Madrid, Campus de Cantoblanco, Madrid 28049, Spain 2 Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Campus de Cantoblanco, Madrid 28049, Spain 3 IMDEA-Nanoscience. Faraday 9, Campus Cantoblanco-UAM, Madrid 28049, Spain © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 18 June 2020 / Revised: 27 July 2020 / Accepted: 2 August 2020
ABSTRACT In the present work we develop an electrochemical assisted method to form nanopores on the surface of highly oriented pyrolytic graphite (HOPG), which was accomplished by a simple electrochemical route and a scalable nanomaterial, carbon nanodots, without applying high voltages, high temperatures or toxic reagents. HOPG electrodes are in a solution of N-enrich carbon nanodots in acidic media and the potential scans applied on HOPG lead to the formation of a spatially inhomogeneous porous surface. The diameter of the resulting nanopores can be tuned by controlling the number of electrochemical reduction cycles. The resulting nanoporous surfaces are characterized by atomic force microscopy, Raman spectroscopy, scanning electrochemical microscopy, electrochemical impedance spectroscopy and electrochemistry. These nanoporous HOPG showed high capacitance. Hence the potential of these surfaces to the development of energy storage devices is demonstrated.
KEYWORDS nanoporous, highly oriented pyrolytic graphite (HOPG), carbon nanodots, supercapacitor
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Introduction
Nowadays, porous materials are gaining interest because they present a great versatility since they have different fields of application as catalysis [1], separators [2], chemical sensor [3], fuel cell [4], batteries [5] and energy storage as supercapacitor [6]. Another important field of application is medicine and biology [7]. Nanoporous coatings are characterized by having numerous cavities of nanometric size that penetrate in the whole material. They provide the material with a large specific area, better conductivity and an increase in the mass transfer coefficient. In addition, the presence of nanopores in a surface can completely modify its basic properties, since they can make it more reactive and change properties such as texture, density and morphology. However, the preparation of a material with these characteristics requires precision. Researchers have adopted either bottom-up or top-down approaches to prepare nanoporous materials. The first one has been employed to build a surface with nanopores already integrated from the beginning, using nanobubbles as templates of polypyrrol film [8], gold nanoparticles grown on highly oriented pyrolytic graphite (HOPG) [9] and three-dimensional (3D) porous
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