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In Situ Atomic-Scale Observation of Phase Evolution in Nickel Phosphide Nanoparticles

Sharma, Kshipra LU ; Hu, Tianyi LU ; Sankhla, Aryan and Dick, Kimberly A. LU (2026) In Nano Letters 26(5). p.1774-1781
Abstract

Nickel phosphides are promising earth-abundant, low-cost catalysts for hydrogen/oxygen evolution reactions and CO2 reduction. However, their formation mechanisms remain poorly understood and difficult to control. This particularly applies to mechanisms determining phase evolution, crystallinity, and morphology under reactive conditions, factors that critically influence catalytic activity and stability. Here, we employ environmental transmission electron microscopy to directly observe the conversion of nickel nanoparticles into nickel phosphide phases under controlled phosphine atmosphere and temperatures. A three-stage Ni-to-Ni2P conversion sequence is observed: (i) surface nucleation, (ii) rapid particle-size... (More)

Nickel phosphides are promising earth-abundant, low-cost catalysts for hydrogen/oxygen evolution reactions and CO2 reduction. However, their formation mechanisms remain poorly understood and difficult to control. This particularly applies to mechanisms determining phase evolution, crystallinity, and morphology under reactive conditions, factors that critically influence catalytic activity and stability. Here, we employ environmental transmission electron microscopy to directly observe the conversion of nickel nanoparticles into nickel phosphide phases under controlled phosphine atmosphere and temperatures. A three-stage Ni-to-Ni2P conversion sequence is observed: (i) surface nucleation, (ii) rapid particle-size expansion, and (iii) crystallographic restructuring and faceting. Phase selectivity depends on the phosphine pressure and temperature: Ni2P forms at both low and high pressures, Ni2P and Ni5P4 coexist at intermediate pressure, and Ni12P5 emerges under no phosphine supply (residual phosphine may have remained) at elevated temperatures. We capture the temperature-driven Ni2P-to-Ni12P5 transition. These insights offer strategies to control the phase and morphology for improved catalytic performance.

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author
; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Earth-abundant catalysts, Environmental transmission electron microscopy (ETEM), Nickel phosphide (NiP) nanoparticles, Phase evolution, Vapor−solid reaction
in
Nano Letters
volume
26
issue
5
pages
8 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:105029926322
  • pmid:41591331
ISSN
1530-6984
DOI
10.1021/acs.nanolett.5c05549
language
English
LU publication?
yes
id
85746b22-b276-4e09-bec5-e54b23f6b70e
date added to LUP
2026-04-17 11:59:35
date last changed
2026-05-29 16:38:15
@article{85746b22-b276-4e09-bec5-e54b23f6b70e,
  abstract     = {{<p>Nickel phosphides are promising earth-abundant, low-cost catalysts for hydrogen/oxygen evolution reactions and CO<sub>2</sub> reduction. However, their formation mechanisms remain poorly understood and difficult to control. This particularly applies to mechanisms determining phase evolution, crystallinity, and morphology under reactive conditions, factors that critically influence catalytic activity and stability. Here, we employ environmental transmission electron microscopy to directly observe the conversion of nickel nanoparticles into nickel phosphide phases under controlled phosphine atmosphere and temperatures. A three-stage Ni-to-Ni<sub>2</sub>P conversion sequence is observed: (i) surface nucleation, (ii) rapid particle-size expansion, and (iii) crystallographic restructuring and faceting. Phase selectivity depends on the phosphine pressure and temperature: Ni<sub>2</sub>P forms at both low and high pressures, Ni<sub>2</sub>P and Ni<sub>5</sub>P<sub>4</sub> coexist at intermediate pressure, and Ni<sub>12</sub>P<sub>5</sub> emerges under no phosphine supply (residual phosphine may have remained) at elevated temperatures. We capture the temperature-driven Ni<sub>2</sub>P-to-Ni<sub>12</sub>P<sub>5</sub> transition. These insights offer strategies to control the phase and morphology for improved catalytic performance.</p>}},
  author       = {{Sharma, Kshipra and Hu, Tianyi and Sankhla, Aryan and Dick, Kimberly A.}},
  issn         = {{1530-6984}},
  keywords     = {{Earth-abundant catalysts; Environmental transmission electron microscopy (ETEM); Nickel phosphide (NiP) nanoparticles; Phase evolution; Vapor−solid reaction}},
  language     = {{eng}},
  number       = {{5}},
  pages        = {{1774--1781}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Nano Letters}},
  title        = {{In Situ Atomic-Scale Observation of Phase Evolution in Nickel Phosphide Nanoparticles}},
  url          = {{http://dx.doi.org/10.1021/acs.nanolett.5c05549}},
  doi          = {{10.1021/acs.nanolett.5c05549}},
  volume       = {{26}},
  year         = {{2026}},
}