Engineering Active Fe Sites on Nickel–Iron Layered Double Hydroxide through Component Segregation for Oxygen Evolution Reaction

Graphical All good in theory and practice ! Theoretical calculations are performed to prove the higher activity of edge Fe sites. The active Fe sites are induced on nickel–iron layered double hydroxide through a facile acid treatment owing to the difference in their solubility product constant. The activity tests show that the samples containing more edge Fe sites exhibit higher oxygen evolution activity. Nickel–iron layered double hydroxide (NiFe LDH) is a promising oxygen evolution reaction (OER) electrocatalyst under alkaline conditions. Much research has been performed to understand the structure–activity relationship of NiFe LDH under OER conditions. However, the specific role of the Fe species remains unclear and under debate. Herein, based on DFT calculations, it was discovered that the edge Fe sites show higher activity towards OER than either the edge Ni sites or lattice sites. Therefore, a facile acid-etching method was proposed to controllably induce the formation of edge Fe sites in NiFe LDH, and the obtained sample exhibited higher OER activity. X-ray absorption near edge structure and extended X-ray absorption fine structure analyses further revealed that the interaction of the edge Fe species with Ni is believed to contribute to the enhancement of the OER performance. This work provides a new understanding of the structure–activity relationship in NiFe LDH and offers a facile method for the design of efficient electrocatalysts in an alkaline environment.