TY - JOUR
T1 - Decay of Ru(BPY)33+ in thin nafion layers catalyzed by Co(II)
AU - Rabani, Joseph
AU - Yoshida, Tsukada
AU - Kaneko, Masao
AU - Kira, Akira
PY - 1994/1
Y1 - 1994/1
N2 - Catalytic oxidation of water by Ru(bpy)33+ in the presence of Co2+ ions, well known in homogeneous solution, has been investigated in thin Nafion layers. Nafion layers on ITO electrodes were equilibrated with Ru(bpy)32+. Ru(bpy)33+ was produced by electrochemical oxidation after which the electrode was transferred into the reaction cell containing buffered Co2+ solution. The build up of Ru(bpy)32+ absorbance at 454 nm was followed spectrophotometrically. The reaction rate is proportional to [Ru(III)], [Co2+] and [HPO42-]. We found no evidence for a pH effect in the range 6–8, and no inhibition by Ru(II). A limiting rate of formation of Ru(II) is observed at high Co2+ or phosphate ion concentrations. At high local concentration of the Ru complex in the Nafion layer (~ 0.5 M), two Ru(II) formation processes are observed, their rates differ by one order, but other features (effects of [Ru(III)], [Ru(II)], [Co2+], phosphate and pH) remain unchanged. These results are in contrast with homogeneous solution where the rate of build up of Ru(II) has been previously reported to be proportional to [Ru(III)], [Co2+] and [OH-]2, and inversely proportional to [Ru(II)]. A mechanism is proposed which accounts for these observations.
AB - Catalytic oxidation of water by Ru(bpy)33+ in the presence of Co2+ ions, well known in homogeneous solution, has been investigated in thin Nafion layers. Nafion layers on ITO electrodes were equilibrated with Ru(bpy)32+. Ru(bpy)33+ was produced by electrochemical oxidation after which the electrode was transferred into the reaction cell containing buffered Co2+ solution. The build up of Ru(bpy)32+ absorbance at 454 nm was followed spectrophotometrically. The reaction rate is proportional to [Ru(III)], [Co2+] and [HPO42-]. We found no evidence for a pH effect in the range 6–8, and no inhibition by Ru(II). A limiting rate of formation of Ru(II) is observed at high Co2+ or phosphate ion concentrations. At high local concentration of the Ru complex in the Nafion layer (~ 0.5 M), two Ru(II) formation processes are observed, their rates differ by one order, but other features (effects of [Ru(III)], [Ru(II)], [Co2+], phosphate and pH) remain unchanged. These results are in contrast with homogeneous solution where the rate of build up of Ru(II) has been previously reported to be proportional to [Ru(III)], [Co2+] and [OH-]2, and inversely proportional to [Ru(II)]. A mechanism is proposed which accounts for these observations.
UR - http://www.scopus.com/inward/record.url?scp=84951610955&partnerID=8YFLogxK
U2 - 10.1163/156856794X00603
DO - 10.1163/156856794X00603
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AN - SCOPUS:84951610955
SN - 0922-6168
VL - 20
SP - 879
EP - 892
JO - Research on Chemical Intermediates
JF - Research on Chemical Intermediates
IS - 8
ER -