Highly Active Ternary Nickel–Iron oxide as Bifunctional Catalyst for Electrochemical Water Splitting

Abstract

The development of noble metal free, robust catalyst is highly sought for commercialization of clean, renewable energy technology and to replace the fossil fuel‐based energy equipments. Herein, we report a highly efficient and stable ternary Nickel Iron oxide (NiFe2O4) electrocatalyst for bifunctional oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline medium. The as‐synthesized NiFe2O4 has been confirmed by techniques like FESEM, HR‐TEM, powder X‐ray diffraction (XRD), and X‐ray photoelectron spectra analysis. NiFe2O4 demonstrate nanoparticle morphology with an average size of ∼10 nm. The synthesized NiFe2O4 electrocatalyst exhibit superior electrocatalytic efficiency for OER, and achieves a current density of 10 mA cm−2 at an overpotential of 290 mV, with smaller Tafel slope of 42 mV/dec. A stable performance of OER is obtained at 10 mA cm−2 for more than 8 h. The electrocatalytic activity of NiFe2O4 is comparable with benchmark electrocatalyst IrO2/C. Similarly, NiFe2O4 also shows superior HER activity in 1 M KOH. The enhanced bi‐functional activity of NiFe2O4 is thought to be the synergy between the multicomponent structure of NiFe2O4, high surface area, and stability leading to high electrical conductivity.

Mesoporous NiFe2O4 with Tunable Pore Morphology for Electrocatalytic Water Oxidation

“…Phase‐purity was also checked by Raman spectroscopy, especially to exclude the presence of hematite by‐phases, since small amounts of hematite in spinel nanocrystals might not be detected by PXRD. For cubic spinels with F d m space group, five Raman active lattice modes were expected: A 1g (691 cm −1 )+ E g (332 cm −1 )+3 T 2g (201 cm −1 , 487 cm −1 , 570 cm −1 ) [54–57] . The A 1g signal corresponds to the symmetric stretching mode of M−O bonds in tetrahedral units.…”

“…For cubic spinels with Fd � 3m space group, five Raman active lattice modes were expected: A 1g (691 cm À 1 ) + E g (332 cm À 1 ) + 3 T 2g (201 cm À 1 , 487 cm À 1 , 570 cm À 1 ). [54][55][56][57] The A 1g signal corresponds to the symmetric stretching mode of MÀ O bonds in tetrahedral units. The T 2g (2) and T 2g (3) signals can be assigned to the asymmetric stretching mode and to the asymmetric bending of MÀ O bonds in octahedral units, respectively.…”

“…The minimum overpotential reached of 410 mV show the potential of NiFe 2 O 4 as an electrocatalyst for water oxidation, since previously reported overpotentials for water oxidation with unmodified NiO or Fe 2 O 3 are much higher. [56]…”

Direct MOCVD Growth of Iron Oxide on Three‐Dimensional Nickel Foam as Electrode for the Oxygen Evolution Reaction

“…[11] Moreover, NiFe 2 O 4 was investigated as a bifunctional electrocatalyst for OER and hydrogen evolution reaction (HER) in alkaline medium. [12] In addition to oxides, iron nickel layered double hydroxides (FeNiO x H y ) have been identified as highly active electrocatalysts for the OER. [13] Unfortunately, nanoparticles have several disadvantages, one of which is that they must be immobilized and electrically connected to the electrode surface.…”

“…Here, Liu et al reported on the hydrothermal growth of spinel NiFe 2 O 4 in the form of nanospindle arrays on FeNi 3 foam, which were successfully applied as electrodes for the OER [11] . Moreover, NiFe 2 O 4 was investigated as a bifunctional electrocatalyst for OER and hydrogen evolution reaction (HER) in alkaline medium [12] . In addition to oxides, iron nickel layered double hydroxides (FeNiO x H y ) have been identified as highly active electrocatalysts for the OER [13] …”