Engineering Lithium Ions Embedded in NiFe Layered Double Hydroxide Lattices To Activate Laminated Ni²⁺ Sites as High‐Efficiency Oxygen Evolution Reaction Catalysts

Abstract

NiFe layered double hydroxides (LDHs) have been denoted as benchmark non‐noble‐metal electrocatalysts for the oxygen evolution reaction (OER). However, for laminates of NiFe LDHs, the edge sites are active, but the basal plane is inert, leading to underutilization as catalysts for the OER. Herein, for the first time, light and electron‐deficient Li ions are intercalated into the basal plane of NiFe LDHs. The results of theoretical calculations and experiments both showed that electrons would be transferred from near Ni2+ to the surroundings of Li+, resulting in electron‐deficient properties of the Ni sites, which would function as “electron‐hungry” sites, to enhance surface adsorption of electron‐rich oxygen‐containing groups, which would enhance the effective activity for the OER. As demonstrated by the catalytic performance, the Li−NiFe LDH electrodes showed an ultralow overpotential of only 298 mV at 50 mA cm−2, which was lower than that of 347 mV for initial NiFe LDHs and lower than that of 373 mV for RuO2. Reasonable intercalation adjustment effectively activates laminated Ni2+ sites and constructs the electron‐deficient structure to enhance its electrocatalytic activity, which sheds light on the functional treatment of catalytic materials.

FeNi-Layered Double-Hydroxide Nanoflakes with Potential for Intrinsically High Water-Oxidation Catalytic Activity

“…Exfoliated/intercalated FeNi LDHs have been investigated to improve OER activities by increasing their number of active sites as well as their electrical/ion conductivity. 6,7,19,31−33 Other methods of enhancing the OER activity of FeNi LDHs via induction of the lattice tensile strain and enriched Fe compositions from the traditional FeNi LDH (Fe/Ni = 1:3 mol/mol) have been reported 6,7,19 Recent research has also focused on amorphous FeNi materials exhibiting much higher OER activities than those of FeNi LDHs. 6 In our research, we have noticed that catalytic electrodes can be evaluated with high experimental reproducibility via controlled microgram-scale mass-loading amounts of catalysts by adopting a simple drop-casting method using diluted dispersion solutions of nanoparticles (NPs) on CP, i.e., direct electrical contact between NPs and a binder-free GDE.…”

A Wet Impregnation Strategy for Advanced FeNi‐Based Electrocatalysts towards Oxygen Evolution

“…Fe‐, Ni‐, and Co‐based compounds are considered to be the most promising candidates for OER catalysts due to their excellent catalytic performance and low cost [15–21] . In recent years, there are many studies about these low‐cost catalysts.…”

“…It was found doping of Se in the synthesized FeOOH can highly improve the catalytic activity [26] . As for doping, another interesting example is that embedding of Li + in NiFe hydroxides can enhance the catalytic activity for OER [16] . Chemical synthesis route with elaborate design can provide effective OER catalysts with favorable microstructures.…”

“…[10][11][12][13][14] Fe-, Ni-, and Co-based compounds are considered to be the most promising candidates for OER catalysts due to their excellent catalytic performance and low cost. [15][16][17][18][19][20][21] In recent years, there are many studies about these low-cost catalysts. Various chemical synthesis strategies including precursor-mediated method, template-assisted route, doping were developed for effective but cheap OER catalysts.…”

“…[26] As for doping, another interesting example is that embedding of Li + in NiFe hydroxides can enhance the catalytic activity for OER. [16] Chemical synthesis route with elaborate design can provide effective OER catalysts with favorable microstructures. Sun et al designed the loading of three-dimensional needle-like CoHPO 4 on nickel foam.…”