Revealing Structural Evolution of Nickel Phosphide-Iron Oxide Core–Shell Nanocatalysts in Alkaline Medium for the Oxygen Evolution Reaction

Authors

• Ryan H. Manso, University of Arkansas, FayettevilleFollow
• Jiyun Hong, Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory
• Wei Wang, Condensed Matter Physics and Materials Science Department , Brookhaven National Laborator
• Prashant Acharya, University of Arkansas, FayettevilleFollow
• Adam S. Hoffman, Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory
• Xiao Tong, Center for Functional Nanomaterials , Brookhaven National Laboratory ,
• Feng Wang, University of Arkansas, Fayetteville
• Lauren F. Greenlee, University of Arkansas, FayettevilleFollow
• Yimei Zhu, Condensed Matter Physics and Materials Science Department , Brookhaven National Laboratory
• Simon R. Bare, Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory
• Jingyi Chen, University of Arkansas, FayettevilleFollow

Document Type

Article

Publication Date

7-9-2024

Keywords

X-ray photoelectron spectroscopy, Metal oxide nanoparticles, Radiology, Nanoparticles, Extended X-ray absorption fine structure

Abstract

Metal phosphide-containing materials have emerged as a potential candidate of nonprecious metal-based catalysts for alkaline oxygen evolution reaction (OER). While it is known that metal phosphide undergoes structural evolution, considerable debate persists regarding the effects of dynamics on the surface activation and morphological stability of the catalysts. In this study, we synthesize NiP_x-FeO_x core–shell nanocatalysts with an amorphous NiP_x core designed for enhanced OER activity. Using ex situ X-ray absorption spectroscopy, we elucidate the local structural changes as a function of the cyclic voltammetry cycles. Our studies suggest that the presence of corner-sharing octahedra in the FeO_x shell improves structural rigidity through interlayer cross-linking, thereby inhibiting the diffusion of OH^–/H₂O. Thus, the FeO_x shell preserves the amorphous NiP_x core from rapid oxidation to Ni₃(PO₄)₂ and Ni­(OH)₂. On the other hand, the incorporation of Ni from the core into the FeO_x shell facilitates absorption of hydroxide ions for OER. As a result, Ni/Fe­(OH)_x at the surface oxidizes to the active γ-(oxy)­hydroxide phase under the applied potentials, promoting OER. This intriguing synergistic behavior holds significance as such a synthetic route involving the FeO_x shell can be extended to other systems, enabling manipulation of surface adsorption and diffusion of hydroxide ions. These findings also demonstrate that nanomaterials with core–shell morphologies can be tuned to leverage the strength of each metallic component for improved electrochemical activities.

Citation

Ryan H. Manso, Jiyun Hong, Wei Wang, Prashant Acharya, Adam S. Hoffman, Xiao Tong, Feng Wang, Lauren F. Greenlee, Yimei Zhu, Simon R. Bare, Jingyi Chen; Revealing Structural Evolution of Nickel Phosphide-Iron Oxide Core–Shell Nanocatalysts in Alkaline Medium for the Oxygen Evolution Reaction. Chem. Mater. 9 July 2024; 36 (13): 6440–6453. https://doi.org/10.1021/acs.chemmater.4c00379

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This work is licensed under a Creative Commons Attribution 4.0 International License.