Evaluating Fe-Site and Vacancy Dependent Intrinsic Activity of NiFe Layered Double Hydroxides through Cavity Microelectrodes.

We report evaluating the intrinsic activity of Ni(OH), NiFe layered double hydroxides (LDHs), and NiFe-LDH having vacancies for oxygen evolution reaction (OER) by the use of cavity microelectrodes (CMEs) with controllable mass loading. The number of active Ni sites () ranging from 1 × 10 to 6 × 10 is quantitatively correlated with OER current, which reveals that the introduction of Fe-sites and vacancies increases the turnover frequency (TOF) from 0.027 to 0.118 and 0.165 s, respectively. Electrochemical surface area (ECSA) is further quantitatively correlated with , which indicates that per unit ECSA () is decreased by the introduction of Fe-sites and vacancies. Therefore, the difference of OER current per unit ECSA () is reduced compared with that of TOF. The results demonstrate that CMEs provide a good platform to evaluate intrinsic activity with TOF, , and more reasonably.