Nanoporous electrodes of phase-dealloyed Fe_83.3-xCo_xSi₄B₈P₄Cu_0.7 (x = 4, 10 and 20 at.%) precursors with superior Redox performances and high stabilities

Co substitutions for Fe_83.3Si₄B₈P₄Cu_0.7 precursors are effective to stabilize the nanoporous structures during dealloying in H₂SO₄ solutions and improve Redox performances of nanoporous electrodes in alkaline conditions. Heterogeneous nanocrystalline structures of Co-substituted Fe_83.3-xCo_xSi₄B₈P₄Cu_0.7 (x = 0, 4, 10 and 20 at.%) alloys consist of two phases: α-Fe(Co) phases and continuously distributed residual amorphous phases. The nanopores on as-dealloyed Fe-Co-Si-B-P-Cu alloys are smaller in size with higher Co concentrations. This is ascribed to the finer α-Fe(Co) phases distributed in the precursor alloys after nanocrystallization. Nanoporous architectures after dealloying inherit the microstructural characteristics of Fe-Co-Si-B-P-Cu precursor alloys. The short-term and long-term CV curves of nanoporous Redox electrodes in 0.5 M KOH solution demonstrate that Redox reactions have been enhanced by partial substitution of Fe by Co and the best Redox performance can be obtained on as-dealloyed Fe_79.3Co₄Si₄B₈P₄Cu_0.7 alloys because of the highest Redox peak current density of 90 mA cm⁻² after 150 CV cycles. However, the stabilities of nanoporous Fe_79.3Co₄Si₄B₈P₄Cu_0.7 electrodes have a predictable decline due to the overgrowth of Fe₃O₄ octahedra and destruction of the ligaments during long-term Redox cycling. On the other hand, the better Redox stabilities has achieved on as-dealloyed Fe_63.3Co₂₀Si₄B₈P₄Cu_0.7 alloys with stable oxidation peak current densities of 45–47 mA cm⁻² from 950 to 3000 CV cycles, about 2.3 times the nanoporous Co-free Fe_83.3Si₄B₈P₄Cu_0.7 electrodes. The stabilities are considered to result from the relatively small Fe₃O₄ octahedra, the stabilization of the amorphous Co₃O₄ outmost layers and the transformation of amorphous and crystalline Co₃O₄ phases during long-term Redox cycling. The Co substitution of Fe_83.3Si₄B₈P₄Cu_0.7 precursor alloys can achieve the high Redox performances and good stabilities of nanoporous electrodes.