Study of the Oxygen Evolution Reaction Catalytic Behavior of Co_xNi_1–xFe₂O₄in Alkaline Medium

Abstract

Catalysts for the oxygen evolution reaction (OER) play an important role in the conversion of solar energy to fuel of earth-abundant water into H and O through splitting/electrolysis. Heterogeneous electrocatalysts for hydrogen and oxygen evolution reactions (HER and OER) exhibit catalytic activity that depends on the electronic properties, oxidation states, and local surface structure. Spinel ferrites (MFeO; M = Ni and Co) based materials have been attractive for the catalytic water oxidation due to their well-known stability in alkaline medium, easy synthesis, existence of metal cations with various oxidation states, low cost, and tunable properties by the desired metal substitution. To understand the better catalytic activity of MFeO in detail the role of Ni and Co was studied through MNiFeO (M = Co; 0 < x < 1), which was prepared by the sol-gel method. The results showed that bare NiFeO has better catalytic activity (η = 381 mV at 10 mA cm and Tafel slope of 46.4 mV dec) compared to Co-containing MNiFeO (η = 450-470 mV at 10 mA cm and Tafel slope of 50-73 mV dec) in alkaline medium, and the substitution of Co is found to suppress the catalytic activity of NiFeO. The degradation of catalytic activity with an increase in Co content was accounted for in further detailed investigations.

An Insight on the Electrocatalytic Mechanistic Study of Pristine Ni MOF (BTC) in Alkaline Medium for Enhanced OER and UOR

“…It is closer to the previous report of Yu et al [73] The smaller Tafel slope of 64 mV dec À1 of Ni MOF than compared to NiO WCP and noble benchmark RuO 2 (126 mV dec À1 ) indicates the better catalytic activity (higher rate in the kinetics) of Ni MOF with the chemical step of OH À surface species rearrangement reaction being the rate determining step in OER. [8,9] Table 1 summarises the measured EIS parameters of catalysts. Figure 6d shows the Nyquist plot (Real (Z') vs. Imaginary (Z")) of catalysts and the representative simple and most common Randles equivalent circuit model given as the inset in Figure 6d.…”

“…[35,48,50] The numerous hydrogen bonding of carboxylate and Ni 2 + yields 3D porous interconnected solid structures. [8,9,37,40,75,76] It is showed by the kinetic charge transfer resistance (R ct ) measurements by the EIS studies under the OER and UOR in the WE and UE respectively. It could be attributed to the formation of Ni(OH) 2 /NiOOH by the Ni 2 + metal bonding between BTC deprotonated form with their size-shape selective binding ability and its resulting structural rigidity under OER condition.…”

“…[1,2] Water electrolysis (WE) has been considered as a promising way to produce high pure H 2 than compared to earlier hydrocarbon and steam reformation process. [2,[4][5][6][7][8][9][10][11] In water electrolysis, anodic 4e À transfer oxygen evolution reaction (OER) is the limiting factor than compared to cathodic 2e À transfer hydrogen evolution reaction (HER). [2,[4][5][6][7][8][9][10][11] In water electrolysis, anodic 4e À transfer oxygen evolution reaction (OER) is the limiting factor than compared to cathodic 2e À transfer hydrogen evolution reaction (HER).…”

Electrochemical Cathodic Treatment of Mild Steel as a Host for Ni(OH)2 Catalyst for Oxygen Evolution Reaction in Alkaline Media

“…During OER, at the applied anodic potential, catalytically active sites of Ni(OH) 2 /NiOOH phase interact with Fe(OH) 2 /FeOOH . The mixture of Fe(OH) 2 /FeOOH and Ni(OH) 2 /NiOOH turn to higher catalytically active phase and improve the conductivity resulting in low charge transfer resistance as evidenced in the EIS studies . In view of the fact, Ni acts as catalyst centre via formation of Ni 2+ /Ni 3+ (Ni−O, NiOO) whereas Fe act as Lewis acid and promote as well as stabilize the neighbouring Ni oxidation state under the OER conditions .…”

Interface Electronic Coupling in Hierarchical FeLDH(FeCo)/Co(OH)2 Arrays for Efficient Electrocatalytic Oxygen Evolution

“…Compared to Co(OH) 2 , the FeLDH(FeCo)/Co(OH) 2 catalysts have much lower R ct at each applied potential, which indicates a fast charge‐transfer reaction during the OER. In the corresponding Bode plots, the FeLDH(FeCo)/Co(OH) 2 catalysts show a clear decrease and shift of phase angles compared with Co(OH) 2 (Figure a2‐d2), which suggests fast electron transfer in the collaborative FeLDH(FeCo)/Co(OH) 2 interface for the conversion of surface‐adsorbed OH − and intermediates . The EIS studies soundly support the previous conclusions made on the basis of LSV, Tafel, and E a analyses.…”