Elucidating the Influence of Intercalated Anions in NiFe LDH on the Electrocatalytic Behavior of OER: A Kinetic Study

The oxygen evolution reaction (OER) as one half-cell reaction of electrochemical water splitting has a fundamental impact on water splitting efficiency and thus on the competitiveness of electrochemically generated hydrogen in the energy market. Nickel-iron layered double hydroxides (NiFe LDH) are among the most promising electrocatalysts for efficient OER under alkaline conditions. Despite intensive research, correlations of the material properties and the resulting kinetically limiting surface processes are poorly investigated. This work focuses on the kinetic behavior of NiFe LDH catalysts containing different anions in the basal spacing in alkaline OER. Steady-state Tafel plots, impedance measurements as well as reaction order plots were used to elucidate differences in the catalytic performance. All catalysts showed a dual Tafel behavior and fractional reaction orders. For kinetic modelling, the physisorbed hydrogen peroxide mechanism and Temkin adsorption model were adopted to fit experimental data. Our study showed that the intercalated anions affect the kinetics of rate determining steps. The hypophosphite intercalated LDH possessed the highest OER activity and the first step as rate determining. While for both carbonate and borate intercalated NiFe LDH, the second step proved to be rate determining in the low Tafel region, while the first step was found to be rate-limiting in the high Tafel region.

Automated summary

Nickel-iron layered double hydroxides (NiFe LDH) are efficient electrocatalysts for alkaline oxygen evolution reaction (OER). This study investigated the kinetic behavior of NiFe LDH catalysts with different intercalated anions using steady-state Tafel plots, impedance measurements, and reaction order plots. The results showed that intercalated anions affect the rate-determining steps and have a significant impact on the OER activity.