TY - JOUR
T1 - Dioxygen reduction and hydrogen peroxide dismutation using electropolymerized bilayers of cobalt + manganese tetrakis(o-aminophenyl)porphyrins
AU - Bettelheim, A.
AU - Ozer, D.
AU - Harth, R.
AU - Ydgar, R.
N1 - Funding Information:
We thank Professor Royce W. Murray for many helpful discussions. This research was supported by grant No. 85-00235 from the United States-Israel Binational Science Foundation (BSF), Jerusalem, Israel.
PY - 1990/3/26
Y1 - 1990/3/26
N2 - Bilayers of electropolymerized cobalt + manganese tetrakis(o-aminophenyl)porphyrins (poly[Co(o-NH2)TPP] + poly[Mn(o-NH2)TPP]) were used for the electrocatalytic reduction of dioxygen. The half-wave potential for O2 reduction at these bilayer films follows that of O2 reduction at single poly[Co(o-NH2)TPP] films in the entire pH range, indicating that this process is governed by the potential of the Co(III)/Co(II) couple in both cases (+0.2 and -0.2 V vs. Ag/AgCl at pHs 2 and 14, respectively). The Co/Mn bilayer porphyrin films are more efficient catalysts than the cobalt porphyrin films in basic solutions, as deduced from the lower peroxide yields (30 and 75% at pH 12 for the Co/Mn and Co porphyrin films, respectively). The addition of 3x10-3 M imidazole decreases the H2O2 yield obtained at the Co/Mn porphyrin bilayers (43 and 30% at pH 13, in the absence and presence of imidazole, respectively). This is attributed to a process in which H2O2 is dismutated by the imidazoleligated manganese porphyrin. The dismutation process is suggested to involve a μ-oxo-manganese(IV or V) porphyrin which is reduced by excess hydrogen peroxide to yield the original Mn(III) porphyrin. Increased stability of the Co/Mn porphyrin bilayer films was observed compared to that of the cobalt porphyrin films: the recorded current for O2 reduction at glassy carbon/film electrodes held for 20 h at -0.3 V vs. Ag/AgCl at pH 10 decreased by 62% and only by 25% at Co and Co/Mn porphyrin films, respectively.
AB - Bilayers of electropolymerized cobalt + manganese tetrakis(o-aminophenyl)porphyrins (poly[Co(o-NH2)TPP] + poly[Mn(o-NH2)TPP]) were used for the electrocatalytic reduction of dioxygen. The half-wave potential for O2 reduction at these bilayer films follows that of O2 reduction at single poly[Co(o-NH2)TPP] films in the entire pH range, indicating that this process is governed by the potential of the Co(III)/Co(II) couple in both cases (+0.2 and -0.2 V vs. Ag/AgCl at pHs 2 and 14, respectively). The Co/Mn bilayer porphyrin films are more efficient catalysts than the cobalt porphyrin films in basic solutions, as deduced from the lower peroxide yields (30 and 75% at pH 12 for the Co/Mn and Co porphyrin films, respectively). The addition of 3x10-3 M imidazole decreases the H2O2 yield obtained at the Co/Mn porphyrin bilayers (43 and 30% at pH 13, in the absence and presence of imidazole, respectively). This is attributed to a process in which H2O2 is dismutated by the imidazoleligated manganese porphyrin. The dismutation process is suggested to involve a μ-oxo-manganese(IV or V) porphyrin which is reduced by excess hydrogen peroxide to yield the original Mn(III) porphyrin. Increased stability of the Co/Mn porphyrin bilayer films was observed compared to that of the cobalt porphyrin films: the recorded current for O2 reduction at glassy carbon/film electrodes held for 20 h at -0.3 V vs. Ag/AgCl at pH 10 decreased by 62% and only by 25% at Co and Co/Mn porphyrin films, respectively.
UR - http://www.scopus.com/inward/record.url?scp=0006377135&partnerID=8YFLogxK
U2 - 10.1016/0022-0728(90)87036-J
DO - 10.1016/0022-0728(90)87036-J
M3 - Article
AN - SCOPUS:0006377135
VL - 281
SP - 147
EP - 161
JO - Journal of Electroanalytical Chemistry
JF - Journal of Electroanalytical Chemistry
SN - 1572-6657
IS - 1-2
ER -