Quasi-reversible two-electron reduction of oxygen at gold electrodes modified with a self-assembled submonolayer of cysteine |
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| Affiliation: | 1. Departamento de Química Orgánica e Inorgánica/IUQOEM, Universidad de Oviedo, E-33071 Oviedo, Spain;2. School of Chemistry, University of Bristol, Bristol BS8 1TS, UK;1. Kyoto University;2. Kagawa University Hospital;3. Chiba University Graduate School of Medicine;1. Institute for Energy Research, Jiangsu University, 301 Xuefu Road, Zhenjiang, 212013, China;2. Chemistry Department, University of the Western Cape, Robert Sobukwe Road, Bellville, 7535, Cape Town, South Africa;1. Department of Chemistry, University of Eastern Finland, Joensuu Campus, PO Box 111, FI-80101 Joensuu, Finland;2. Department of Chemistry, University of Jyväskylä, PO Box 35, FI-40014 Jyväskylä, Finland;1. School of Materials Science and Engineering, Sun Yat-sen University, Guangdong 510275, PR China;2. Physical Chemistry and Center for Advancing Electronics Dresden, TU Dresden, Bergstr. 66b, 01062 Dresden, Germany;3. Laboratory of Green Chemistry, School of Engineering Science, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli, Finland;4. Laboratory of Applied Environmental Chemistry, University of Eastern Finland, Patteristonkatu 1, FI-50100 Mikkeli, Finland;5. Department of Civil and Environmental Engineering, Florida International University, Miami, FL, 33174, USA;6. Helmholtz-Zentrum Dresden − Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstraße 400, 01328 Dresden, Germany;1. Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000 São Paulo, SP, Brazil;2. Department of Biochemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000 São Paulo, SP, Brazil;3. Department of Chemistry ICET, Universidad Autonoma de Guadalajara, Patria 1201, Lomas del Valle, Zapopan, Jalisco, Mexico;4. Institute of Engineering, Universidad Autonoma de Baja California, Blvd. B. Juarez y Calle de la Normal s/n, Mexicali, BC, Mexico |
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| Abstract: | The electrochemical reduction of molecular oxygen (O2) has been performed at gold electrodes modified with a submonolayer of a self-assembly (sub-SAM/Au) of a thiol compound (typically cysteine (CYST)) in O2-saturated 0.5 M KOH. At bare gold electrode O2 reduction reaction proceeds irreversibly, while this reaction is totally hindered at gold electrodes with a compact structure of CYST over its surface. The partial reductive desorption of the compact CYST monolayer was achieved by controlling the potential of the CYST/Au electrode, leading to the formation of a submonolayer coverage of the thiol compound over the Au electrode surface (sub-SAM/Au), at which the CYST molecules selectively block the Au(1 0 0) and Au(1 1 0) fractions (the so-called rough domains) of the polycrystalline Au while the Au(1 1 1) component (the so-called smooth domains) remains bare (i.e., uncovered with CYST). This sub-SAM/Au electrode extraordinarily exhibits a quasi-reversible two-electron reduction of molecular oxygen (O2) in alkaline medium with a peak separation (ΔEp) between the cathodic and anodic peak potentials (Epc,Epa) of about 60 mV. The ratio of the anodic current to the cathodic one is close to unity. The formal potential (Eo′) of this reaction is found to equal −150 mV vs. Ag/AgCl/KCl(sat.). |
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