Genuine Active Species Generated from Fe₃N Nanotube by Synergistic CoNi Doping for Boosted Oxygen Evolution Catalysis

Abstract

The surface reconstruction of oxygen evolution reaction (OER) catalysts has been proven favorable for enhancing its catalytic activity. However, what is the active site and how to promote the active species generation remain unclear and are still under debate. Here, the in situ synthesis of CoNi incorporated Fe3N nanotubes (CoNi–Fe3N) on the iron foil through the anodization/electrodeposition/nitridation process for use of boosted OER catalysis is reported. The synergistic CoNi doping induces the lattice expansion and up shifts the d‐band center of Fe3N, which enhances the adsorption of hydroxyl groups from electrolyte during the OER catalysis, facilitating the generation of active CoNi–FeOOH on the Fe3N nanotube surface. As a result of this OER‐conditioned surface reconstruction, the optimized catalyst requires an overpotential of only 285 mV at a current density of 10 mA cm−2 with a Tafel slope of 34 mV dec−1, outperforming commercial RuO2 catalysts. Density functional theory (DFT) calculations further reveal that the Ni site in CoNi–FeOOH modulates the adsorption of OER intermediates and delivers a lower overpotential than those from Fe and Co sites, serving as the optimal active site for excellent OER performance.

Dynamic Surface Chemistry of Catalysts in Oxygen Evolution Reaction

“…There are other electrocatalysts that show a similar phenomenon of cation doping and leaching, enabling the fast surface reconstruction and ultimately enhancing the OER performance. For instance, CoNi doping in Fe 3 N induces the lattice expansion and modulates the electronic structure of Fe 3 N, helping optimize the adsorption of hydroxyl groups from the electrolyte in the OER process, and thus motivating the rapid and efficient surface reconstruction into CoNi–FeOOH on the Fe 3 N surface [14a] . In addition, Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3‐ δ electrocatalyst exhibits a degree of leaching of the Ba 2+ and Sr 2+ ions to form a flexible perovskite structure with a large oxygen vacancy content, leading to a rapid surface evolution into an amorphous oxyhydroxide after a few cycles during OER [15a] .…”

“…Compared with the common crystalline metal oxides/(oxy)hydroxide, these reconstruction‐derived counterparts possess more oxygen vacancies, which can help tune the interactions between surficial sites and oxygen intermediates, promoting a higher electrocatalytic activity. [ 14 ] Therefore, a thorough understanding on the actual reconstruction, which is the key part of the dynamic surface chemistry, is vitally important in design and development of efficient OER electrocatalysts ( Figure ).…”

Coordination Polymer-Derived Fe3N Nanoparticles for Efficient Electrocatalytic Oxygen Evolution

“…The Ni 3 FeN-NPs exhibited high performance for OER with a low overpotential of 280 mV at 10 mA cm –2 in 1 M KOH . However, the synthesis of metal nitrides is generally through the chemical vapor deposition (CVD) method in the presence of expensive, volatile, and flammable NH 3 gas. ,, It is worthy seeking a safer alternative nitrogen source and exploring a novel method to synthesize metal nitrides. Furthermore, so far, the OER catalysis mechanism for metal nitrides is unclear since their Gibbs free energies for the adsorption of intermediates are too large.…”

Electrochemical preparation of nano/micron structure transition metal-based catalysts for the oxygen evolution reaction

“…IrO 2 and RuO 2 are the most advanced OER electrocatalysts with low overpotentials and low Tafel slopes, especially under acidic conditions. 15–17 However, these catalysts have the disadvantages of scarcity and high cost and cannot be used for industrial production to obtain economic hydrogen energy resources. 18 However under alkaline conditions, some transition metal-based electrocatalysts have excellent catalytic performance when catalyzing the OER and excitingly often outperform precious metal-based electrocatalysts.…”