Acid-Corrosion-Induced Hollow-Structured NiFe-Layered Double Hydroxide Electrocatalysts for Efficient Water Oxidation

Abstract

Highly active, cost-effective, and stable electrocatalyst for oxygen evolution reaction (OER) is of primary importance in electrochemical water splitting. Although the direct growth of active components on the substrate is an effective strategy to enhance the catalytic activity, the weak adhesion between active material and substrate tremendously hampers their long-term utilization with excellent performance. Herein, a three-dimensional (3D) hollow structure of NiFe-layered double hydroxide (NiFe LDH) on NiFe foam (NiFe LDH@NiFe) is designed via acid-corrosion-induced strategy. The self-supported electrode was obtained through a process based on an autologous NiFe foam, in which the electrode/gas/electrolyte interface and electrocatalyst/substrate interface are delicately engineered. Remarkably, the NiFe LDH@NiFe only needs an ultralow overpotential of 201 mV to deliver a current density of 10 mA cm–2 for OER in 1 M KOH electrolyte, along with superb stability. The high catalytic activity is attributed to the intimate connection between the nanosheet arrays and substrate, superior intrinsic activity, and fast electron transfer. More importantly, the excellent hydrophilicity and aerophobicity of NiFe LDH@NiFe enables significantly improved infiltration of electrolytes, quick release of oxygen bubbles, and remarkably enhanced charge transfer. Thus, the obtained NiFe LDH@NiFe holds promise for electrocatalytic applications. Finally, the growth mechanism of NiFe LDH@NiFe is investigated and discussed in detail.

Superhydrophilic/Superaerophobic Hierarchical NiP2@MoO2/Co(Ni)MoO4 Core–Shell Array Electrocatalysts for Efficient Hydrogen Production at Large Current Densities

“…Considering the superior HER activity of NiP 2 @MoO 2 /Co­( Ni )­MoO 4 cuboid arrays, we suppose to combine it with the state-of-the-art OER catalyst to assemble a two-electrode cell and investigate its overall water splitting (OWS) performance. As Ni/Fe layered double hydroxides (LDHs) are a kind of prospective OER catalysts, a NiFe-LDH electrode through a special acid etching method with splendid OER properties was prepared by our previous work Figure S14 shows its SEM image and OER polarization curve.…”

“…Chronopotentiometry measurement was conducted at a fixed current density of −200 mA cm –2 for 650 h and a multistep galvanostatic measurement was employed to investigate the reversibility of electrocatalysts at different operating current densities. Finally, we used the NiP 2 @MoO 2 /Co­( Ni )­MoO 4 and the NiFe LDH reported by our previous work as the cathode and anode, respectively, to assemble a two-electrode system for overall water splitting performance tests. Polarization curves were obtained by LSV without iR correction.…”

“…37 Chronopotentiometry measurement was conducted at a fixed current density of −200 mA cm −2 for 650 h and a multistep galvanostatic measurement was employed to investigate the reversibility of electrocatalysts at different operating current densities. Finally, we used the NiP 2 @MoO 2 /Co(Ni)MoO 4 and the NiFe LDH reported by our previous work 38 electrocatalysts remain the same bouquet-like structure with cuboid array morphology except that the surface of the cuboid became rough after phosphorization. The cuboids varied in thickness and length, ranging from 0.1 to 5 μm and 10 to 50 μm, respectively.…”

“…As Ni/Fe layered double hydroxides (LDHs) are a kind of prospective OER catalysts, a NiFe-LDH electrode through a special acid etching method with splendid OER properties was prepared by our previous work. 38 Figure S14 shows its SEM image and OER polarization curve. It only requires an overpotential of 138 mV to afford a current density of 10 mA cm −2 .…”

Surface Reconstruction of an FeNi Foam Substrate for Efficient Oxygen Evolution

“…The contrast between Figure e,f under the same magnification clearly shows that the NSs compactly cover the surface of the substrate. This vertical NS array structure can accelerate electron transfer and expose more active sites. ,, The elemental mapping images in Figure S1 (Supporting Information) show that Fe, Ni, and O are uniformly dispersed on sr -FNF46. Similarly, sr -FNF28, sr -FNF64, and sr -FNF82 also exhibit numerous NSs, which can be distinctly seen in Figures S2–S4, respectively.…”