Defect Engineering of Oxygen Vacancies in Ultrathin NiFe-Layered Double Hydroxides: Insights from Density Functional Theory

Abstract

Defects and interface engineering in layered double hydroxides (LDH) are crucial for the rational search for functional electrocatalysts. Despite the known enhancement of LDH activity by oxygen vacancies (Ov), a formal exploration of how vacancy content influences electrocatalytic properties is lacking. Herein, density functional theory (DFT) calculations were employed to investigate the impact of the Ov content (1−5%) on the electronic structure, electrocatalytic activity of NiFe LDH, and interface coupling with heteroatom-doped carbon. Calculations revealed that the density of states and bandwidth of defect levels induced within the band gap depend on the Ov content, influencing the adsorption of oxygenated species and calculated overpotentials for the oxygen evolution reaction (OER), predicted to be three times less than that of the defect-free system. Additionally, binding energy calculations highlight heightened interactions between Ov-enriched LDH and doped-carbon surfaces, causing electron density redistribution and Fermi level shifts due to doping effects. Carbon modification with pyridinic nitrogen and phosphorus is a promising candidate for enhanced interface engineering with defective LDH, attributed to the larger interaction energy and alignment of its Fermi level with the valence band of LDH, underscoring the key role of pyridinic nitrogen in the carbon support and enhanced electronic conductivity in LDH/carbon composites.