Inherent Oxygen Vacancies Boost Surface Reconstruction of Ultrathin Ni-Fe Layered-Double-Hydroxides toward Efficient Electrocatalytic Oxygen Evolution

Abstract

Unraveling structure-related reconstruction during oxygen evolution reaction (OER) and its correlation with intrinsic electrocatalytic activity is of great significance for designing better catalysts but unfortunately remains elusive. Herein, ultrathin Ni-Fe layered-double-hydroxides (LDH) with inherent oxygen vacancies (V O ) are successfully fabricated via coprecipitation under a controlled manner, which accomplish a quite low overpotential of 230 mV at 10 mA cm −2 in 1.0 M KOH and perform among the best of recently reported nonprecious electrocatalysts. During the OER, inherent V O is experimentally and theoretically evidenced to boost surface reconstruction and the operando formation of p−n interfaces (i.e., γ-Ni-Fe LDH/α-Ni-Fe LDH) via deprotonation. On such reconstructed interfaces, the V O in both surface γ-Ni-Fe LDH and bulk α-Ni-Fe LDH can alter the electron densities of metal sites and subsequently optimize the free energies of a multistep OER pathway, which accounts for the boosted OER activity and, more importantly, identifies the correlation of electrocatalysis with both the catalyst surface and bulk.

Electronic structure engineering for electrochemical water oxidation

“…verified oxygen vacancies in NiFe LDH by analyzing the O1s XPS spectrum. 174 Electron paramagnetic resonance (EPR) spectroscopy is commonly used to elucidate oxygen vacancies in nanomaterials. 175 For example, Xiao et al 176 and X-ray Absorption Near Edge Structure (XANES) analysis have become an invaluable and effective characterization method to check the changes in the electronic structure around the active center.…”

“…Recently, Gao et al verified oxygen vacancies in NiFe LDH by analyzing the O1s XPS spectrum. 174 Electron paramagnetic resonance (EPR) spectroscopy is commonly used to elucidate oxygen vacancies in nanomaterials. 175 For example, Xiao et al 176 used EPR to prove the existence of oxygen vacancies in electrocatalysts.…”

Influence of Co2+, Cu2+, Ni2+, Zn2+, and Ga3+ on the iron-based trimetallic layered double hydroxides for water oxidation

“…The decrease in catalytic activity can be due to the detachment of the catalyst from the electrode as O 2 evolves. 49,50 Additional studies should be done to investigate the deactivation pathways of these materials.…”

Low Overpotential Overall Water Splitting by a Cooperative Interface of Cobalt-Iron Hydroxide and Iron Oxyhydroxide

“…This positive shift in Fe 2p 3/2 indicates the increase in electron density around the Fe atoms in CoFe-OH@FeOOH as opposed to CoFe-OH due to elevated oxygen vacancy. 50 The high-resolution O 1s spectrum further confirms oxygen vacancies in CoFe-OH@FeOOH. The O 1s spectrum shows prominent characteristic peaks at 530.2, 531.8, and 533.2 eV corresponding to metal-oxygen (M-O), oxygen defects (OH À ), and water molecules absorbed on the surface (H 2 O), respectively (Figure 1E).…”