Abstract
Herein, we report an iron/nickel/zinc mixed oxide as a catalyst for the electrochemical water oxidation. This catalyst was synthesized by a straightforward method for the synthesis of an iron/nickel/zinc mixed oxide through the calcination of a Fe/Ni/Zn organometallic compound. The calcined product contains Fe and Ni as crucial ions for water oxidation, accompanied by the presence of Zn ions. The removal of Zn ions from the mixed oxide provides more active sites on the surface of the catalyst. The composition of the compound was characterized by some common methods and found to be an efficient water-oxidizing catalyst. The catalyst on FTO at pH = 13 yields a current density of 12 mA/cm2 at 1.2 V (vs. Ag│AgCl). After 5 hours at 1.1 V, the electrode not only shows no decrease in performance, but also shows an increase from 4 to 7 mA/cm2 in the water oxidation activity. Tafel plot, for the electrode at pH = 13 in KOH solution (0.1 M) showed linearity for the graph of lg j vs. V with both relatively low (220.4 mV per decade) and high overpotentials (903.7 mV per decade).
Highlights
Switching from fossil fuels to renewable energies is an inevitable task that should be performed in the near future to provide clean and sustainable energies for human beings
It was reported that diphenylphosphine moieties on cyclopentadienyl rings of dppf (1,1′-Bis(diphenylphosphino)ferrocene) make the oxidation of iron to be more difficult than ferrocene in 1,2-dichloroethane solvent[30,31,32]
1 has indicated irreversible anodic peaks in cyclic voltammetry (CV) which are attributed to a decomposition reaction in acetonitrile (Fig. S2a) (ESI†)
Summary
Switching from fossil fuels to renewable energies is an inevitable task that should be performed in the near future to provide clean and sustainable energies for human beings. Some research groups previously reported that Ni/Fe (oxy)hydroxides have the lowest overpotential toward water oxidation under the alkaline conditions[10,11,12,13,14]. Ni/Fe (oxy)hydroxides are used as the precursors to synthesize the other phases of Ni/Fe oxides[15], nitrides[16] and sulfides[17] These oxides are applied in hydrogen evolution and photoelectrochemical water splitting[18,19]. In this context, Corrigan et al firstly investigated the catalytic activity of Ni/Fe (oxy)hydroxides for water oxidation in the 1980s20–22. (oxy)hydroxides have been employed in the development of an electrolyzer having a voltage below 1.5 V with a single AAA battery[25] and high-performance rechargeable Zn–air batteries[26]
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