Enhanced Redox properties of amorphous Fe_63.3-83.3Co_0-20Si₄B₈P₄Cu_0.7 alloys via long-term CV cycling

Effect of partial substitution of Fe by Co on the Redox properties and cyclicity of amorphous Fe_83.3Si₄B₈P₄Cu_0.7 alloy has been investigated in 0.5 M KOH solution by short-term and long-term cyclic voltammetry (CV). Redox performance of amorphous Fe_83.3-xCo_xSi₄B₈P₄Cu_0.7 (x = 0, 1, 4, 10 and 20 at.%) alloys is enhanced by the partial substitution of Fe by Co of 1–20 at.%, and the best chemical composition is considered to be Fe_79.3Co₄Si₄B₈P₄Cu_0.7 on the basis of the highest Redox peak current density after short-term CV cycling. The flake-shaped FeOOH, CoOOH and/or Fe-oxides and Co-oxides form and become more and more with an increasing of the cycle numbers. After 3000 cycles of the long-term CVs, amorphous Fe_79.3Co₄Si₄B₈P₄Cu_0.7 alloy also exhibits the superior and stable Redox properties with two times higher oxidation peak current densities than amorphous Fe_83.3Si₄B₈P₄Cu_0.7 alloy. Redox peak current densities after long-term CV cycling are enhanced more than 200 times due to the octahedral crystalline Fe₃O₄, Co₃O₄ and CoO with a large surface area in comparison to those after the short-term CVs. The substitution of Fe by 4 at.% Co is considered to be the optimal chemical composition for the enhancement of Redox properties and high stability during the long-term CV cycling.