Engineering Bimetallic NiFe‐Based Hydroxides/Selenides Heterostructure Nanosheet Arrays for Highly‐Efficient Oxygen Evolution Reaction

Abstract

Developing cost‐effective and high‐efficiency electrocatalysts toward alkaline oxygen evolution reaction (OER) is crucial for water splitting. Amorphous bimetallic NiFe‐based (oxy)hydroxides have excellent OER activity under alkaline media, but their poorly electrical conductivity impedes the further improvement of their catalytic performance. Herein, a bimetallic NiFe‐based heterostructure electrocatalyst that is composed of amorphous NiFe(OH)x and crystalline pyrite (Ni, Fe)Se2 nanosheet arrays is designed and constructed. The catalyst exhibits an outstanding OER performance, only requiring low overpotentials of 180, 220, and 230 mV at the current density of 10, 100, and 300 mA cm−2 and a low Tafel slope of 42 mV dec−1 in 1 m KOH, which is among the state‐of‐the‐art OER catalysts. Based on the experimental and theoretical results, the electronic coupling at the interface that leads to the increased electrical conductivity and the optimized adsorption free energies of the oxygen‐contained intermediates plays a crucial role in enhancing the OER activities. This work focusing on improving the OER performance via engineering amorphous‐crystalline bimetallic heterostructure may provide some inspiration for reasonably designing advanced electrocatalysts.

Single‐Atom Doping and High‐Valence State for Synergistic Enhancement of NiO Electrocatalytic Water Oxidation

“…Meanwhile, there has been a significant decline in the intensity, suggesting that there are obvious changes in the coordination conditions of the Ni atoms during the voltage increase from 1.34 to 1.45 V. According to the absorption edge of the Ni K‐edge XANES plots in Figure S22a in the Supporting Information, the edges for 1.34 and 1.37 V have almost no shift, while the conditions of 1.43 and 1.45 V show an obvious right‐shift, suggesting an increase of the valence state of Ni as the voltage rises from 1.37 to 1.43 V. Based on the polarization plot of Ir@IrNiO (Figure 4a), it is in the water absorbing stage at 1.34 V and changes into the Ni 3+ to Ni 4+ step at 1.37 V; after that, it will be O–O formation and O 2 evolution. Thus, the surface Ni 3+ sites first absorb OH groups to form Ni 3+ –OH and then Ni 4+ –O at 1.34 and 1.37 V, and at the conditions of 1.43 and 1.45 V, they change into Ni 4+ sites [ 48,51,52 ]…”

Design of NiFe‐based nanostructures for efficient oxygen evolution electrocatalysis

“…All these compounds are converted to NiFe-based oxides or hydroxides during the catalytic process, and these anions largely contribute to the catalytic reaction at the anode, so the research for more and more abundant anion tuning continues. [20,23,[28][29][30][31][32][33][34][35] The enhanced OER activity of NiFe-based sulfides is due to the increase in electrochemical surface area and defects during the reaction as well as the decrease in catalyst grain size. For NiFe-based oxides/(oxy)hydroxides, FeOOH as an active site is too strong for the adsorption of OH* intermediates generated during electrocatalytic reactions and may impair their OER properties.…”

“…[75] The heterogeneous structure consisting of amorphous structure and crystalline phase structure could both increase the number of active sites and keep the structure of the catalyst stable during the reaction. [31,76,77] Zou et al reported a facile method to prepare the nanocomposite (Ni-Fe-OH@Ni 3 S 2 /NF) that consisted of amorphous Ni-Fe-OH and Ni 3 S 2 nanosheet arrays. Ni-Fe-OH@Ni 3 S 2 /NF showed remarkable OER activity at current densities of up to 1000 mA/cm 2 .…”

“…[76] The structure consisting of amorphous NiFe(OH) x and crystalline (Ni, Fe)Se 2 also has very favorable OER activity. [31] In the hierarchical g) The polarization LSV curves recorded for Co-C@NiFe LDH nanofibers before and after 1000 CV cycles. Reproduced with permission.…”

Quasi‐Parallel NiFe Layered Double Hydroxide Nanosheet Arrays for Large‐Current‐Density Oxygen Evolution Electrocatalysis

“…Compared to their bulk counterparts, self‐supporting nanoarray electrodes are particularly suitable as large‐current‐density OER catalysts because of their abundant exposed active sites and enhanced surface permeability. Consequently, Ni/Fe‐based hydroxides have been the target of intense research focus [15–24] . In addition to increasing the surface activity and active sites, forming a strong coupling interaction between substrate and electrocatalyst (i. e., substrate effect) is a facile way to enhance the electrocatalytic performance of the self‐supported electrode [12] .…”