Iron‐Doped Nickel Phosphide Nanosheets In Situ Grown on Nickel Submicrowires as Efficient Electrocatalysts for Oxygen Evolution Reaction

Abstract

Tens of micrometers long metallic Ni submicrowires with a diameter of approximately 200 nm are prepared by a chemical reduction method under a magnetic field. Fe‐doped Ni2P nanosheets are then in situ grown on Ni submicrowires by a simple wet‐chemical reaction followed by a low‐temperature phosphorization process. The (Ni0.87Fe0.13)2P–Ni composite exhibits the highest catalytic activity toward oxygen evolution reaction in alkaline solution among all the as‐prepared (Ni1−xFex)2P–Ni catalysts, delivering a current density of 10 mA cm−2 at an overpotential of only 257 mV and keeping high stability over 10 h electrolysis. These exceptional activities are attributed to the unique structure combining metallic Ni submicrowires as good electronically conductive substrate and the in situ grown Fe‐doped Ni2P nanosheets. Specifically, Fe incorporation leads to strong electron interactions between Ni, Fe, and P, fast reaction kinetics, small charge‐transfer resistance, and a large electrochemical surface area, which are responsible for the excellent catalytic performance.

Phosphorus‐Based Electrocatalysts: Black Phosphorus, Metal Phosphides, and Phosphates

“…[ 132 ] For example, the lower electrical impedance of Ni 0.6 Co 1.4 P compared to that of Ni 2 P suggested a better conductivity and rapider charge‐transfer kinetic by the Co substitution, which was also validated by the increase in DOS intensity of Ni 0.6 Co 1.4 P. [ 133 ] ii) The activation barrier can be substantially lowered relative to its monometal counterpart by the synergistic effect. [ 134,135 ] In the ternary Fe‐Co‐P alloy, the OH bond cleavage and O–O bond formation could be modulated by tuning the energetics of intermediates (*OH, *O, *OOH), in which the adsorption on a single FeOOH species is too strong, while that on single Co‐based sites is too weak. Consequently, the overpotential of the Fe‐Co‐P catalyst was only 252 mV for achieving 10 mA cm −2 , outperforming most of the previously reported OER catalysts.…”

“…By tuning the amount of P source and temperature, different phases of nickel phosphides and cobalt phosphides can be synthesized. [ 118,120 ] To introduce additional metals into the metal phosphides, multimetallic phosphides can be fabricated by a wet‐chemical procedure combined with subsequent in situ phosphorization reaction, [ 131,205 ] such as NiCo 2 P x nanowire arrays, [ 206 ] and 1D (Ni x Fe 1– x ) 2 P. [ 134 ] For instance, in the hydrothermal process (one of the common wet‐chemical procedures), by adding relevant metal salts in the mixture/solution, bimetallic precursors were obtained, including Ni–Fe hydroxide, [ 111,207 ] NiCo 2 O 4 , [ 92 ] NiCu LDH, [ 96 ] and Fe 1– x Co x LDH. [ 123,140 ] In addition to the hydrothermal approach, electrodeposition approach has been adopted a lot to prepare the bimetallic hydroxide/oxide precursors.…”

Recent developments in metal phosphide and sulfide electrocatalysts for oxygen evolution reaction

“…For four electrons water oxidation reaction, a catalyst containing multiple redox-active metal ions can buffer the multi-electron transfer processes necessary for OER [86]. Metal doping seems as an effective strategy to achieve the purpose that multiple redox-active metal ions exist in the OER catalysts [85,[87][88][89][90][91][92][93][94][95]. Li and co-workers [89] successfully synthesized the homogeneous ternary Fe2−xMnxP nanorods with control of Mn incorporation (0 ≤ x ≤ 0.9) from the solution-phase reaction of manganese and iron carbonyl complexes with trioctylphosphine.…”

Coupling of Nickel Boride and Ni(OH)2 Nanosheets with Hierarchical Interconnected Conductive Porous Structure Synergizes the Oxygen Evolution Reaction

“…Electrochemical water splitting is a promising large‐scale energy storage technique involving the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), in which the electrical energy generated from renewable energy sources, such as solar and wind, can be converted to the chemical energy reserved in hydrogen . However, this hydrogen production scheme is still mainly hindered by the sluggish kinetics of OER coupled with a 4 electron and 4 proton process, contributing to the significant overpotential loss for water electrolysis .…”