Electrocatalytic Performance and Kinetic Behavior of Anion-Intercalated Borate-Based NiFe LDH in Alkaline OER

The synthesis of hydrogen via water electrolysis is an important step towards resolving the energy crisis and impeding global warming, as hydrogen can be used as a green energy carrier. The oxygen evolution as one half-cell reaction (OER) is currently limiting efficient water splitting due to kinetic inhibition as well as a complex mechanism, causing a large overpotential. Nickel-iron layered double hydroxides (LDH) were found to be suitable OER catalysts, as they are cost effective, stable and highly active. This work focuses on the intercalation of different organic and inorganic borates into the LDH interlayers to study their influence on OER. Besides activity and stability measurements, three borate candidates were chosen for a kinetic study, including steady-state Tafel analysis and reaction order plots. It was found that the Bockris pathway with the second step as rate-determining step was predominant for all three catalysts. Of all candidates, the intercalation of borate resulted in the highest performance, which was associated with a high reducibility affecting the active metal sites.