Electrochemical properties of glassy carbon, nickel and gold electrodes modified with aryl groups
Date
2010-08-02
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Abstract
Klaassüsinik-, nikkel- ja kuldelektroodide pinna modifitseerimiseks arüülrühmadega kasutati vastavate diasooniumisoolade elektrokeemilist redutseerumist. Hapniku redutseerumist uuriti fenüül-, naftüül-, antratsenüül-, bifenüül-, 4-bromofenüül, 4-detsüülfenüül- ja 4-nitrofenüülrühmadega modifitseeritud klaassüsinikelektroodidel, kasutades pöörleva ketaselektroodi meetodit. Võrdleval eesmärgil uuriti ka Fe(CN)6 3-/4- redokspaari ning dopamiini elektrokeemilist käitumist. Arüülrühmadega modifitseeritud elektroodide blokeerivad omadused omavad suurt tähtsust mitmetes kasutusvaldkondades, näiteks elektrokatalüüsis ja elektroanalüüsis.
Klaassüsinikelektroodi spontaanne modifitseerimine antrakinooniga viidi läbi sukeldades elektroode erinevateks ajavahemikeks vastava diasooniumisoola lahusesse. Spontaanselt modifitseeritud antrakinooni elektrokatalüütiline efekt hapniku redutseerumisele klaassüsinikelektroodidel oli võrreldav elektrokeemiliselt modifitseeritud antrakinooni puhul saadud tulemustega. Sarnased tulemused saadi ka in situ sünteesitud antrakinooni diasooniumsooladega modifitseeritud klaassüsinikelektroodidel. Atsetonitriilis ja happelises vesikeskkonnas modifitseeritud elektroodid näitasid sarnast elektrokatalüütilist aktiivsust hapniku redutseerumisel 0,1 M KOH lahuses.
Hapniku redutseerumist uuriti ka antrakinooniga modifitseeritud nikkelelektroodidel ning täheldati kõrget elektrokatalüütililist aktiivsust sellele reaktsioonile. Nikkelelektroodi pinda modifitseeriti ka 4-nitrofenüülrühmadega. Modifitseeritud elektroodid näitasid häid blokeerivaid omadusi Fe(CN)6 3-/4- redokspaari laenguülekandeprotsessile.
Diasooniumisoola redutseerumise meetodil modifitseeriti ka kuldelektroode. Arüülkilede kasvamist kullal iseloomustati kvartsmikrokaalude meetodiga. Arüülkile kasvu ja paksuse uurimiseks kasutatud aatomjõumikroskoopiline meetod näitas, et moodustunud arüülkile ei ole kompaktne, vaid pigem „mügarlik“ ning hõredalt pakitud. Tulemusi kinnitasid ka röntgenfotoelektronspektroskoopilised mõõtmised, mis demonstreerisid 4-bromofenüül- ja 4-nitrofenüülrühmade kõrgeid pindkontsentratsioone kulla pinnal. Hapniku redutseerumine arüülkiledega modifitseeritud kuldelektroodidel oli inhibeeritud väiksemal määral kui Fe(CN)6 3-/4- ja dopamiini redokspaaride laenguülekandeprotsess.
The surface of glassy carbon (GC), nickel and gold electrodes was modified with aryl groups using the electrochemical reduction of the corresponding diazonium salts. The reduction of oxygen was studied on phenyl, naphthyl, anthracenyl, biphenyl, 4-bromophenyl, 4-decylphenyl and 4-nitrophenyl modified GC electrodes using the rotating disk electrode method. For comparison purposes the electrochemical response of the Fe(CN)6 3-/4- and dopamine redox probes on aryl modified GC electrodes was also investigated. The blocking behaviour of aryl films is of paramount importance in many fields, including electrocatalysis and electroanalysis. The spontaneous grafting of GC surface with anthraquinone (AQ) was achieved by immersion of the substrate in the solutions of its diazonium derivative for different periods of time. The electrocatalytic effect of spontaneously grafted anthraquinone on oxygen reduction was comparable to that of the electrochemically grafted electrodes. The modification of glassy carbon with in situ generated anthraquinone diazonium cations was analogous to that using previously synthesised anthraquinone diazonium salts. Electrodes modified in acetonitrile and in aqueous acidic solution showed similar electrocatalytic activity for oxygen reduction in 0.1 M KOH. The reduction of oxygen was studied on AQ modified nickel electrodes and a high electrocatalytic activity for this reaction was observed. The Ni electrode surface was also modified with nitrophenyl (NP) groups. The blocking action of NP films for the Fe(CN)6 3-/4- redox system was in evidence. The surface of Au electrodes was also modified with aryl groups using the diazonium reduction method. The EQCM results gave further insight into the growth of these films on gold. AFM studies of the film growth revealed that the aryl films do not grow uniformly and a rather granular growth is evident, which does not result in compact but rather loosely packed film. This finding is supported by XPS studies that demonstrated high surface concentration of bromophenyl and nitrophenyl groups. The barrier properties of aryl films on Au were studied, revealing that O2 reduction was inhibited to a lesser extent than the electron transfer kinetics of the Fe(CN)6 3-/4- and dopamine redox probes.
The surface of glassy carbon (GC), nickel and gold electrodes was modified with aryl groups using the electrochemical reduction of the corresponding diazonium salts. The reduction of oxygen was studied on phenyl, naphthyl, anthracenyl, biphenyl, 4-bromophenyl, 4-decylphenyl and 4-nitrophenyl modified GC electrodes using the rotating disk electrode method. For comparison purposes the electrochemical response of the Fe(CN)6 3-/4- and dopamine redox probes on aryl modified GC electrodes was also investigated. The blocking behaviour of aryl films is of paramount importance in many fields, including electrocatalysis and electroanalysis. The spontaneous grafting of GC surface with anthraquinone (AQ) was achieved by immersion of the substrate in the solutions of its diazonium derivative for different periods of time. The electrocatalytic effect of spontaneously grafted anthraquinone on oxygen reduction was comparable to that of the electrochemically grafted electrodes. The modification of glassy carbon with in situ generated anthraquinone diazonium cations was analogous to that using previously synthesised anthraquinone diazonium salts. Electrodes modified in acetonitrile and in aqueous acidic solution showed similar electrocatalytic activity for oxygen reduction in 0.1 M KOH. The reduction of oxygen was studied on AQ modified nickel electrodes and a high electrocatalytic activity for this reaction was observed. The Ni electrode surface was also modified with nitrophenyl (NP) groups. The blocking action of NP films for the Fe(CN)6 3-/4- redox system was in evidence. The surface of Au electrodes was also modified with aryl groups using the diazonium reduction method. The EQCM results gave further insight into the growth of these films on gold. AFM studies of the film growth revealed that the aryl films do not grow uniformly and a rather granular growth is evident, which does not result in compact but rather loosely packed film. This finding is supported by XPS studies that demonstrated high surface concentration of bromophenyl and nitrophenyl groups. The barrier properties of aryl films on Au were studied, revealing that O2 reduction was inhibited to a lesser extent than the electron transfer kinetics of the Fe(CN)6 3-/4- and dopamine redox probes.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
doktoritööd, elektroodid, elektrokeemia