Atomic cation and anion co-vacancy defects boosted the oxide path mechanism of the oxygen evolution reaction on NiFeAl-layered double hydroxide†

The oxide path mechanism (OPM) of the oxygen evolution reaction (OER) can overcome the scaling relation limit in the adsorbate evolution mechanism (AEM) and avoid forming oxygen vacancies in the lattice oxygen mechanism (LOM), which enables the catalyst to have both good OER activity and stability. However, there are currently few reports on the OPM for LDH catalysts. In this work, uniformly distributed atomic Al–O–Fe co-vacancies (V_Al–O–Fe) on NiFeAl-LDH nanosheets are constructed by chemical etching and a successive electroreduction method. The obtained material only requires 223 mV to reach 500 mA cm⁻² for the OER. The in situ electrochemical-Raman and chemical probe demonstrate the oxygen evolution reaction follows the OPM pathway. The theoretical calculation results show that the V_Al–O–Fe can shorten the adjacent interatomic distance of bimetallic sites in Ni₆Fe₂Al-LDH, and thus triggers the O–O coupling on the bimetallic sites. Our study provides a novel strategy to trigger the OPM of the OER by introducing uniform co-vacancy defects on the catalysts.