Mechanism and Kinetics of HER and OER on NiFe LDH Films in an Alkaline Electrolyte

Abstract

The mechanism and kinetics of hydrogen evolution (HER) and oxygen evolution (OER) reactions on nickel iron layered double hydroxide (NiFe LDH) in a basic electrolyte are investigated. The deposited film reported an overpotential of 247 and 245 mV at 10 mA/cm 2 toward the HER and OER, respectively. A least squares procedure was performed to fit a theoretical current density model with experimental linear sweep voltammetry (LSV) results, and the chemical reaction rate constants for the OER and HER steps were identified. Electrochemical impedance spectroscopy (EIS) measurements were taken at different potentials, and the resulting kinetic model demonstrates a good agreement between theoretically calculated faradaic resistance and experimental EIS results. The HER results indicated the Heyrovsky step as rate controlling, with a dependence of reaction mechanism on potential. At low potential, the mechanism begins with a Volmer step, followed by parallel Tafel and Heyrovsky steps. At higher potential, the mechanism becomes consecutive combination of the Volmer and Heyrovsky steps. The OER data point to the formation of the adsorbed peroxide as rate controlling. The HER and OER kinetic data were combined into a model capable of predicting the electrolysis cell current-potential characteristics, which can be used for process design and optimization.

Platinum Modulates Redox Properties and 5‐Hydroxymethylfurfural Adsorption Kinetics of Ni(OH)2 for Biomass Upgrading

“…These two crucial steps could be reflected in the paired peaks in the Bode plot and two semi-circular arcs in Nyquist plots.A ccording to the internal relationship of diverse species, reactions,a nd reaction interfaces, the OER interface in the lowfrequencyr egion and the surface oxidation interface in the highfrequencyr egion could be distinguished (Figure 5a,S 9c, S9d, S10c and S10d). [27] With the intervention of HMF,t he accumulation of Ni-(OH)O to form NiO x (OH) y is hindered and presents only one electron transfer interface as the electrode-related electrons are not evolved in subsequent spontaneous reaction (Figure 5b,S9a, S9b,S 10a and S10b). [28] Fort he OER system of Ni(OH) 2 (Figure 5c and S9c), it can be seen that the phase angle of Bode plots corresponding to the high-frequencyi nterface decreases as the potential increases (the reaction rate increasing).…”

“…These two crucial steps could be reflected in the paired peaks in the Bode plot and two semi-circular arcs in Nyquist plots.A ccording to the internal relationship of diverse species, reactions,a nd reaction interfaces, the OER interface in the lowfrequencyr egion and the surface oxidation interface in the highfrequencyr egion could be distinguished (Figure 5a,S 9c, S9d, S10c and S10d). [27] With the intervention of HMF,t he accumulation of Ni-(OH)O to form NiO x (OH) y is hindered and presents only one electron transfer interface as the electrode-related electrons are not…”

Metamorphosis of Heterostructured Surface‐Mounted Metal–Organic Frameworks Yielding Record Oxygen Evolution Mass Activities

“…The EEC used in this work, also known as Armstrong‐Henderson EEC, accounts for the electrolyte resistance ( R s ), a double layer impedance ( Z dl ), a charge transfer resistance ( R ct ), adsorption resistance ( R a ), and the adsorption capacitance ( C a ). [ 70,71 ] A representative Nyquist plot measured at 1.58 V is shown and fitted according to the EEC model (Figure 7A). As an outcome of the fit, the adsorption capacitances C a for the different catalyst films are presented in Figure 7B, Figure S22B,D (Supporting Information) as a function of the applied potential.…”

Dopamine‐Assisted Coral Films of Cobalt as Bifunctional Electrodes for Overall Water Splitting

“…These numbers reveal that there is ultrafast charge transfer during the surface reaction kinetics. [ 42,43 ] The R ct value of S1 is almost half of S2, in OER, indicating that the reaction kinetics for gas evolution is faster in the former electrode. Further, the independent measurements of C dl and the specific capacitance ( C s ) help to estimate the electrochemical surface area (ECSA) of a given electrode.…”