Constructing Ultrathin W-Doped NiFe Nanosheets via Facile Electrosynthesis as Bifunctional Electrocatalysts for Efficient Water Splitting

Abstract

Exploring cost-effective and efficient bifunctional electrocatalysts via simple fabrication strategies is strongly desired for practical water splitting. Herein, an easy and fast one-step electrodeposition process is developed to fabricate W-doped NiFe (NiFeW)-layered double hydroxides with ultrathin nanosheet features at room temperature and ambient pressure as bifunctional catalysts for water splitting. Notably, the NiFeW nanosheets require overpotentials of only 239 and 115 mV for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, to reach a current density of 10 mA/cm2 in alkaline media. Their exceptional performance is further demonstrated in a full electrolyzer configuration with the NiFeW as both anode and cathode catalysts, which achieves a low cell voltage of 1.59 V at 10 mA/cm2, 110 mV lower than that of the commercial IrO2 (anode) and Pt (cathode) catalysts. Moreover, the NiFeW nanosheets are superior to various recently reported bifunctional electrocatalysts. Such remarkable performances mainly ascribe to W doping, which not only effectively modulates the electrocatalyst morphology but also engineers the electronic structure of NiFe hydroxides to boost charge-transfer kinetics for both the OER and HER. Hence, the ultrathin NiFeW nanosheets with an efficient fabrication strategy are promising as bifunctional electrodes for alkaline water electrolyzers.

Oxygen Vacancies and Interface Engineering on Amorphous/Crystalline CrOx‐Ni3N Heterostructures toward High‐Durability and Kinetically Accelerated Water Splitting

“…[ 28 ] The OER polarization curves from high to low potentials (from 1.725 to 0.925 V vs RHE) to avoid possible interferences of the oxidation peak. [ 29 ] From the polarization curves, it is found that the CrO x ‐Ni 3 N‐2 possesses excellent electrochemical performance, which is not only superior to the Ni 3 N, CrO x ‐Ni 3 N‐1, and CrO x ‐Ni 3 N‐3 but also exceeds the IrO 2 electrocatalyst ( Figure a). To drive the current density of 50 mA cm −2 , the CrO x ‐Ni 3 N‐2 needs a small overpotential of 308 mV, which is much lower than 362, 328, and 438 mV required for the CrO x ‐Ni 3 N‐1, CrO x ‐Ni 3 N‐3, and Ni 3 N, respectively (Figure 6b), and is also comparable to recently reported non‐noble OER catalysts (Table S6, Supporting Information).…”

Hollow Mo-doped NiSx nanoarrays decorated with NiFe layered double-hydroxides for efficient and stable overall water splitting

“…To avoid the inuence of the nickel oxidation peak, the LSV data are collected by backward sweep. 58 As depicted in Fig. 5a and b, the Mo-NiS x @NiFe LDH/NF electrode requires a much smaller overpotential of 224 mV to acquire 10 mA cm À2 , while NF, NiMoO 4 $xH 2 O/NF, NiFe LDH/NF, Mo-NiS x / NF and IrO 2 /NF require larger overpotentials of 374, 252, 260, 237 and 268 mV, respectively.…”

High‐Alkaline Water‐Splitting Activity of Mesoporous 3D Heterostructures: An Amorphous‐Shell@Crystalline‐Core Nano‐Assembly of Co‐Ni‐Phosphate Ultrathin‐Nanosheets and V‐ Doped Cobalt‐Nitride Nanowires

“… Electrochemical evaluations of the prepared electrocatalysts for OER: A) iR‐corrected LSV profiles, B) magnified LSV profiles of A for determining the overpotentials at current densities of 10 and 50 mA cm −2 , C) overpotential comparison at 10 mA cm −2 with recently reported electrocatalysts such as Co 0.5 (V 0.5 ), [ 50 ] Co 2 P@Co/N‐C/GC, [ 51 ] exfoliated NiCo‐LDH, [ 52 ] Ni 3 FeN/N‐G, [ 53 ] and Ni 2 P‐CoP/GC, [ 54 ] D) Tafel plots, E) EIS spectra (inset shows the corresponding equivalent impedance circuit diagram), [ 47 , 48 , 49 ] F) current density versus scan rate profiles for the evaluation of C dl , G) long‐term CP stability test of CoNiPO x @V 3% ‐Co 4 N/NF for 50 h duration at a current density of 10 mA cm −2 , G 1 ,G 2 ) low‐ and high‐magnification FE‐SEM images of CoNiPO x @V 3% ‐Co 4 N/NF after CP stability test, and H) comparison of LSV profiles of CoNiPO x @V 3% ‐Co 4 N/NF before and after long‐term CP stability test, 1000 CV and 10 000 CV cycles. …”

“…The lowest Tafel slope of CoNiPO x @V 3% ‐Co 4 N/NF signifies its faster electrochemical kinetics for the OER compared with that of the other developed electrocatalysts. In alkaline media, the OER is generally considered to occur at an active site (*), starting with a PCET process by the aqua species that are absorbed at its surface and subsequent formation of the O—O bond, schematically represented by the following reaction steps: [ 46 ] Furthermore, the EIS spectra of the electrocatalysts were also recorded, and their corresponding Nyquist plots were fitted with an equivalent circuit diagram similar to previous reports, [ 47 , 48 , 49 ] as shown in Figure 5E . Compared with all the prepared samples, the amorphous‐shell@crystalline‐core CoNiPO x @V 3% ‐Co 4 N/NF showed the smallest semicircular region, which indicated its lowest charge‐transfer resistance ( R ct ) and faster electrokinetics (Figure 5E ).…”