3D Self‐Supported Fe‐Doped Ni₂P Nanosheet Arrays as Bifunctional Catalysts for Overall Water Splitting

Abstract

The development of highly efficient bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial for improving the efficiency of overall water splitting, but still remains challenging issue. Herein, 3D self-supported Fe-doped Ni 2 P nanosheet arrays are synthesized on Ni foam by hydrothermal method followed by in situ phosphorization, which serve as bifunctional electrocatalysts for overall water splitting. The as-synthesized (Ni 0.33 Fe 0.67 ) 2 P with moderate Fe doping shows an outstanding OER performance, which only requires an overpotential of ≈230 mV to reach 50 mA cm −2 and is more efficient than the other Fe incorporated Ni 2 P electrodes. In addition, the (Ni 0.33 Fe 0.67 ) 2 P exhibits excellent activity toward HER with a small overpotential of ≈214 mV to reach 50 mA cm −2 . Furthermore, an alkaline electrolyzer is measured using (Ni 0.33 Fe 0.67 ) 2 P electrodes as cathode and anode, respectively, which requires cell voltage of 1.49 V to reach 10 mA cm −2 as well as shows excellent stability with good nanoarray construction. Such good performance is attributed to the high intrinsic activity and superaerophobic surface property.Herein, we fabricated self-supported Fe-doped Ni 2 P nanosheet arrays on the Ni foam by simple hydrothermal method and in situ phosphorization. The performance of Fe-doped Ni 2 P nanosheet arrays as bifunctional catalysts toward overall water splitting depends strongly on the Fe doping ratio in the Ni 2 P. The optimized Fe doping of Ni 2 P [(Ni 0.33 Fe 0.67 ) 2 P] showed excellent HER activity with an overpotential of ≈214 mV to reach 50 mA cm −2 and superior OER performance with a lower overpotential of ≈230 mV to reach 50 mA cm −2 , outperforming the commercial Ir/C. As expected, the electrolyzer using Ni 2 P nanosheet arrays with 31.7% Fe doping as both anode and cathode electrodes for catalyzing overall water splitting exhibited the best performance, obtaining a current density of 10 mA cm −2 at 1.49 V, better than the integration of commercial Pt/C and Ir/C electrodes.

3D Architectures of Quaternary Co‐Ni‐S‐P/Graphene Hybrids as Highly Active and Stable Bifunctional Electrocatalysts for Overall Water Splitting

“…Highly efficient water electrolysis generally requires high-performance electrocatalysts with low overpotential, fast kinetics, and high stability. [9][10][11] Recently, transition-metal hydroxides, [7,12] phosphides, [8,[13][14][15][16] nitrides, [17,18] and chalcogenides [19][20][21][22] have been investigated as promising candidates for bifunctional electrocatalysts. [7,8] The search for earth-abundant, lowcost HER and OER electrocatalysts that are robust, have high activity and stability has triggered numerous efforts to replace noble metal-based materials.…”

One‐Step Synthesis of NiFe Layered Double Hydroxide Nanosheet Array/N‐Doped Graphite Foam Electrodes for Oxygen Evolution Reactions

“…The mass transport and diffusion issue during OER should also be considered since it occurs at the triple‐phase boundary regions . To enhance the diffusion of liquid reactants and gas products, directly fabricating the active species with three dimensional (3D) architecture on free‐standing conductive substrates as integrated electrodes has been explored . Concomitantly, the active sites are adequately exposed by constructing 3D nanostructures; the electrochemically active surface area, penetration of electrolyte, and transportation of electron are also increased by the binder‐free characteristic .…”

Strong Electronic Interaction in Dual‐Cation‐Incorporated NiSe2 Nanosheets with Lattice Distortion for Highly Efficient Overall Water Splitting

“…[22,23] For example, density functional theory (DFT) calculations show that the sites where Se atoms are at the edges of transition metal selenides are HER active sites. [29][30][31] In this case, it is expected that Exploring highly efficient and low-cost electrocatalysts for electrochemical water splitting is of importance for the conversion of intermediate energy. Indeed, incorporation of heterogeneous metal atoms can induce atomic distortions due to strain and result in additional exposed active sites.…”

“…[24] Furthermore, it has been shown that the heterogeneous metal atoms doping could optimize the hydrogen adsorption kinetic energy and improve the HER catalytic activity in comparison to monometallic ones. [29][30][31] In this case, it is expected that Exploring highly efficient and low-cost electrocatalysts for electrochemical water splitting is of importance for the conversion of intermediate energy. Moreover, the electronic interaction between each element in mono-cation-doped electrocatalysts has been always ignored.…”