Proton Pump for O₂ Reduction Catalyzed by 5,10,15,20‐Tetraphenylporphyrinatocobalt(II)

Abstract

Oxygen reduction: A polarized water|1,2‐dichloroethane (DCE) interface acts as a proton pump for the [Co(tpp)] (TPP=5,10,15,20‐tetraphenylporphyrinato) catalyzed O2 reduction by ferrocene (Fc) compounds to produce H2O2 (see figure; IT=ion transfer, ET=electron transfer). This system favours the collection of H2O2 by extraction immediately after its formation in DCE to the adjacent water phase.magnified imageThe role of 5,10,15,20‐tetraphenylporphyrinatocobalt(II) ([Co(tpp)]) as a catalyst on molecular oxygen (O2) reduction by ferrocene (Fc) and its two derivatives, 1,1′‐dimethylferrocene (DFc) and decamethylferrocene (DMFc) at a polarized water|1,2‐dichloroethane (DCE) interface has been studied. The water|DCE interface essentially acts as a proton pump controlled by the Galvani potential difference across the interface, driving the proton transfer from water to DCE. [Co(tpp)] catalyzed O2 reduction by Fc, DFc and DMFc is then followed to produce hydrogen peroxide (H2O2). The catalytic mechanism is similar to that proposed by Fukuzumi et al. for bulk reactions. This interfacial system provides a platform for a very efficient collection of H2O2, by extraction immediately after its formation in DCE to the adjacent water phase, thus decreasing the possibility of degradation and further reaction with ferrocene derivatives.

Scanning electrochemical microscopy determination of hydrogen flux at liquid|liquid interface with potentiometric probe

“…Bis(triphenylphosphoranylidene)ammonium tetrakis(pentafluorophenyl)borate (BATB) was prepared by metathesis of bis(triphenylphosphoranylidene)ammonium chloride (Sigma-Aldrich) and lithium tetrakis(pentafluorophenyl)borate (LiTB) (ABCR) following the procedure described earlier [19] and recrystallized twice from acetone. 1,2-Dichloroethane (DCE, N99%+), and HClO 4 (70%) were obtained from Sigma-Aldrich.…”

Oxygen reduction by decamethylferrocene at liquid/liquid interfaces catalyzed by dodecylaniline

“…In the case of DMFc, it has been shown that oxygen reduction at the polarized water/DCE interface produces decamethylferrocenium (DMFc + ) and hydrogen peroxide (H 2 O 2 ), on the basis of two-phase reactions [7] and in situ detection of H 2 O 2 using scanning electrochemical microscopy [13]. The catalytic effect of various porphyrin compounds, such as cobalt tetraphenylporphyrin [9,14], cobalt porphine [15] and free base tetraphenylporphyrin [16] and electrodeposited platinum particles [8], on the oxygen reduction by DMFc at the water/DCE interface has also been investigated. Moreover, it has been found very recently that under anaerobic conditions DMFc could also reduce aqueous proton to produce hydrogen at the water/DCE interface [17].…”

Hydrogen evolution catalyzed by electrodeposited nanoparticles at the liquid/liquid interface

“…For example, it has been shown that oxygen and proton could be reduced to hydrogen peroxide and hydrogen by the strong electron donor decamethylferrocene (DMFc) at the water/1,2-dichloroethane (DCE) interface under aerobic and anaerobic conditions, respectively. 2,3 In the case of oxygen reduction, the catalytic effect of in situ generated interfacial Pt nanoparticles 6 and that of different metalated 4,5,8,9 and freebase porphyrins 7,10 have also been demonstrated, showing that both adsorbed Pt particles and porphyrins can act as oxygen binding sites.…”