NiFe₂O₄ Nanoparticles/NiFe Layered Double-Hydroxide Nanosheet Heterostructure Array for Efficient Overall Water Splitting at Large Current Densities

Abstract

Constructing catalysts with new and optimizational chemical components and structures, which can operate well for both the anodic oxygen evolution reaction (OER) and the cathodic hydrogen evolution reaction (HER) at large current densities, is of primary importance in practical water splitting technology. Herein, the NiFeO nanoparticles/NiFe layered double hydroxide (LDH) nanosheet heterostructure array on Ni foam was prepared via a simple one-step solvothermal approach. The as-prepared heterostructure array displays high catalytic activity toward the OER with a small overpotential of 213 mV at 100 mA cm and can afford a current density of 500 mA cm at an overpotential of 242 mV and 1000 mA cm at 265 mV. Moreover, it also presents outstanding HER activity, only needing a small overpotential of 101 mV at 10 mA cm, and can drive large current densities of 500 and 750 mA cm at individual overpotentials of 297 and 314 mV. A two-electrode electrolyzer using NiFeO nanoparticles/NiFe LDH nanosheets as both the anode and the cathode implements active overall water splitting, demanding a low voltage of 1.535 V to drive 10 mA cm, and can deliver 500 mA cm at 1.932 V. The NiFeO nanoparticles/NiFe LDH nanosheet array electrodes also show excellent stability against OER, HER, and overall water splitting at large current densities. Significantly, the overall water splitting with NiFeO nanoparticles/NiFe LDH nanosheets as both the anode and the cathode can be continuously driven by a battery of only 1.5 V. The intrinsic advantages and strong coupling effects of NiFeO nanoparticles and NiFe LDH nanosheets make NiFeO nanoparticles/NiFe LDH nanosheet heterostructure array abundant catalytically active sites, high electronic conductivity, and high catalytic reactivity, which remarkably contributed to the catalytic activities for OER, HER, and overall water splitting. Our work can inspire the optimal design of the NiFe bimetallic heterostructure electrocatalyst for application in practical water electrolysis.

Facile Dynamic Synthesis of Homodispersed Ni3S2 Nanosheets as a High‐Efficient Bifunctional Electrocatalyst for Water Splitting

“…X‐ray photoelectron spectroscopy (XPS) patterns of Ni 3 S 2 /NF‐DH are presented in Figure a.‐d. In the Ni 2p spectrum (Figure b), the peaks at 855.7 and 873.3 eV are assigned to the Ni 2p 3/2 and Ni 2p 1/2 respectively, which mainly correspond to the characteristic of Ni 2+ . The additional peak located at 870.1 eV corresponds to Ni + .…”

“…In the Ni 2p spectrum (Figure 3b), the peaks at 855.7 and 873.3 eV are assigned to the Ni 2p 3/2 and Ni 2p 1/2 respectively, which mainly correspond to the characteristic of Ni 2 + . [18] The additional peak located at 870.1 eV corresponds to Ni + . [19] The peak at 852.8 eV can be attributed to the metallic Ni 0 .…”

Fe‐Doped Ni3S2 Nanowires with Surface‐Restricted Oxidation Toward High‐Current‐Density Overall Water Splitting

“…During the reaction, The oxygen dissolved in the solution can oxidize Fe 2 + ions into Fe 3 + ions. [36] Meanwhile, the sulfide ions released from thiourea reacted with exposed Ni on the surface of Ni foam, hence, Ni 3 S 2 nuclei were produced, [13] with Fe 3 + ions doped into the lattice. The citrate ions coordinated on Fe-doped Ni 3 S 2 nuclei made them preferentially grow along the (110) direction, forming Fe-doped Ni 3 S 2 nanowires.…”

“…A piece of Ni foam (NF, 2 × 3 cm) was cleaned before use according to our previous report. [36] thiourea (1.5 mmol), FeSO 4 · 7H 2 O (0.5 mmol) and trisodium citrate dihydrate (0.025 g) were added into solvents of methanol (15 mL) and deionized water (20 mL). After magnetic stirring for 30 min, the above solution was decanted into Teflon-line stainless-steel autoclave with a volume of 40 mL, and put into treated Ni foam.…”

Interface Electronic Coupling in Hierarchical FeLDH(FeCo)/Co(OH)2 Arrays for Efficient Electrocatalytic Oxygen Evolution

“…However, in this mutual doping method, it is hard to keep a balance between the catalytic activity and stability. On the other hand, hybrid and/or multi‐shell catalysts modified and combined with different materials have attracted increasing attention . Many hybrid catalysts, such as FeOOH/Co/FeOOH, Ag/Co(OH) 2 , NiFe 2 O 4 /NiFe layered double hydroxide (LDH), FeOOH/NiFe LDHs, Cu@NiFe LDH, and Am‐CFDH/NCNTs, have been prepared.…”