Revealing the Dynamics and Roles of Iron Incorporation in Nickel Hydroxide Water Oxidation Catalysts

Abstract

The surface of an electrocatalyst undergoes dynamic chemical and structural transformations under electrochemical operating conditions. There is a dynamic exchange of metal cations between the electrocatalyst and electrolyte. Understanding how iron in the electrolyte gets incorporated in the nickel hydroxide electrocatalyst is critical for pinpointing the roles of Fe during water oxidation. Here, we report that iron incorporation and oxygen evolution reaction (OER) are highly coupled, especially at high working potentials. The iron incorporation rate is much higher at OER potentials than that at the OER dormant state (low potentials). At OER potentials, iron incorporation favors electrochemically more reactive edge sites, as visualized by synchrotron X-ray fluorescence microscopy. Using X-ray absorption spectroscopy and density functional theory calculations, we show that Fe incorporation can suppress the oxidation of Ni and enhance the Ni reducibility, leading to improved OER catalytic activity. Our findings provide a holistic approach to understanding and tailoring Fe incorporation dynamics across the electrocatalyst–electrolyte interface, thus controlling catalytic processes.

Synthesis of NiSe2/Fe3O4 Nanotubes with Heteroepitaxy Configuration as a High‐Efficient Oxygen Evolution Electrocatalyst

“…These in situ formed oxyhydroxides could also serve as active sites and improve the OER activity of the catalyst. [15,57] Moreover, the decrease of the Se content in the catalyst indicates the leaching of the Se species from the catalyst into the electrolyte where it may oxidize to SeO 3 2− ions. Due to its good adsorption ability, the SeO 3 2− ions may be adsorbed back to the surface of the catalyst during the OER catalysis, where it could promote the adsorption of the intermediates.…”

Pearson’s Principle-Inspired Robust 2D Amorphous Ni-Fe-Co Ternary Hydroxides on Carbon Textile for High-Performance Electrocatalytic Water Splitting

“…In addition, we further tested the electrocatalytic hydrogen evolution reaction (HER) performance of monadic and binary metal hydroxides, and their performance is shown in Figures S1 and S2 . It can be seen that 3D transition metal base hydroxides, such as Ni, Co, and Fe, have quite high activity, since Fe 3+ can broaden the interlaminar space of 2D materials and enhance their mass transfer behavior [ 54 ]. Meanwhile, the synergistic effect between Fe and the LDH lamellar structure can shorten the ion transport distance at the nanometer scale, so that Fe-doping can further improve its catalytic performance.…”

Effects of Electrochemical Conditioning on Nickel-based Oxygen Evolution Electrocatalysts

“…The NiOxHy layer derived from the NiSe precatalyst layer can have porous morphology with more defect/edge sites that are favorable for Fe incorporation in comparison with the NiOxHy layer derived from a Ni foil substrate. 3,59,[61][62][63][64] Also, it was observed that the Fe composition of 100-NiSe/Ni-CV was higher than that of 100-NiSe/Ni-CP as the Fe composition of Ni-CV was higher than that of Ni-CP. This finding again confirms that CV with both anodic and cathodic potential sweeps is more favorable for Fe incorporation than CP with only anodic potential applied.…”