Homogeneous catalysis of cathodic reduction of oxygen in copper–cystamine aqueous solutions

Abstract

The copper cystamine complex is a suitabIe system for the homogeneous catalysis of oxygen cathodic reduction in aqueous solutions. A steady state cathodic current density of 3.2 mAlcm2 at 0.2V and an overvoltage decrease of 400mV was observed in oxygen-saturated solutions of equimolar concentrations of CuII ions and cystamine (5 x mol dm-3) at pH 4.5. For a given value of C1-ion concentration and pH the catalytic current can be expressed by :The optical, magnetic and kinetic properties of the catalyst were investigated. The results suggest that the CuII ion, although initially reduced to CuI, is stabilized by the disulphide bridge. It is also suggested that because the bridge is a two electron mediator for the reduction of oxygen, the potential barrier of the first electron reduction can be overcome.

The mechanism of the copper ion catalyzed autoxidation of cysteine in alkaline medium

“…The valence state of copper in these chrsters is usually assumed to be Cu(f). However, there are indications that Cu(II) clusters also are abIe to bind dixygen and promote electron transfer horn the hgands towards the dioxygen [33,34].…”

Catalysis of Oxygen Cathodic Reduction in Cobalt Ammoniacal Solutions

“…Usually these electrodes are coated with catalytic layers (1)(2)(3) or are immersed in catalytic suspensions (4,5) to overcome their great deviation from thermodynamic reversibility. The homogeneous catalysis of the oxygen electrode is treated in previous studies (6,7).…”

“…Two types of electrodes (1.0 • 2.8 cm each) were prepared (1): the noncatalytic electrode (type A) was a Ni gauze on which carbon was deposited, and the catalytic one (type B) was a similar electrode but impregnated with Fe(III)-PhC. The instrumentation is described elsewhere (6,8).…”

Oxygen reduction reaction catalyzed with titanyl phthalocyanines in nonaqueous and aqueous media

“…7,[12][13][14][15] Although studies on heterogeneous catalysts (catalyst immobilized on the electrode) are numerous in the literature and most of them are in aqueous solution, [16][17][18] homogenous catalysts (catalyst in solution) for ORR in aprotic media are rare. [19][20][21][22][23] For example, Mho S. and coworkers reported the interaction of reduced cobaltphthalocyanine with oxygen and proposed that the catalytic activities of phthalocyanines are achieved through a conventional regenerative catalytic mechanism. 24 Nyokong and her coworkers also studied the homogeneous catalytic activities of various metalloporphyrin (MPP) complexes in aqueous solution.…”