Ultrathin, Polycrystalline, Two-Dimensional Co 3 O 4 for Low-Temperature CO Oxidation

Yafeng Cai, Jia Xu, Yun Guo, Jingyue Liu

Research output: Contribution to journalArticle

Abstract

Free-standing, hierarchical, ultrathin, and two-dimensional (2D) polycrystalline Co 3 O 4 flowers were synthesized by a hydrothermal and topotactic transformation process. Aberration-corrected electron microscopy study of both the CoO x precursor structure and the subsequent topotactic transformation processes revealed the nucleation and growth mechanisms of the 2D polycrystalline Co 3 O 4 nanosheets. The free-standing flower-shaped CoO x powders (1-5 μm) consist of numerous self-assembled nanocrystallites (average size ∼1.8 nm). After the topotactic transformation, via a rapid calcination process, the powders maintained their hierarchical flower-like shape, but the CoO x nanocrystallites structurally transformed into ultrathin 2D Co 3 O 4 nanoplates with thicknesses ranging from 1 to 5 nm (average thickness ∼2.4 nm). The final, free-standing, ultrathin 2D polycrystalline Co 3 O 4 flowers possess a BET surface area of 138 m 2 /g. Statistical structural analyses revealed that the exposed surfaces of the Co 3 O 4 flowers are dominated by the Co 3 O 4 {112} (∼70%). The hierarchical Co 3 O 4 flowers contain many grain boundaries, pockets, surface steps, and other types of surface defects. CO oxidation on the as-synthesized hierarchical Co 3 O 4 flowers showed a specific activity (normalized to the surface area) of 0.377 μmol·m -2 ·s -1 , about 5 times that of the most active Co 3 O 4 at 70 °C reported in literature. Furthermore, even under moisture-saturated condition (∼3% H 2 O), the ultrathin 2D Co 3 O 4 catalyst demonstrated a high specific rate and is stable for at least 40 h at 90 and 150 °C. The abundance of accessible coordinatively unsaturated Co 3+ , active oxygen species, and surface defects on the polycrystalline Co 3 O 4 {112} nanosheets are responsible for the experimentally observed high catalytic activity.

Original languageEnglish (US)
Pages (from-to)2558-2567
Number of pages10
JournalACS Catalysis
Volume9
Issue number3
DOIs
StatePublished - Mar 1 2019
Externally publishedYes

Fingerprint

Carbon Monoxide
Oxidation
Nanocrystallites
Nanosheets
Surface defects
Powders
Temperature
Aberrations
Calcination
Electron microscopy
Reactive Oxygen Species
Catalyst activity
Grain boundaries
Nucleation
Moisture
Catalysts
Oxygen

Keywords

  • catalysis
  • CO oxidation
  • Co O
  • electron microscopy
  • grain boundaries
  • two-dimensional materials

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

Cite this

Ultrathin, Polycrystalline, Two-Dimensional Co 3 O 4 for Low-Temperature CO Oxidation . / Cai, Yafeng; Xu, Jia; Guo, Yun; Liu, Jingyue.

In: ACS Catalysis, Vol. 9, No. 3, 01.03.2019, p. 2558-2567.

Research output: Contribution to journalArticle

Cai, Yafeng ; Xu, Jia ; Guo, Yun ; Liu, Jingyue. / Ultrathin, Polycrystalline, Two-Dimensional Co 3 O 4 for Low-Temperature CO Oxidation In: ACS Catalysis. 2019 ; Vol. 9, No. 3. pp. 2558-2567.
@article{11d15f0ad597444490dae3d181174764,
title = "Ultrathin, Polycrystalline, Two-Dimensional Co 3 O 4 for Low-Temperature CO Oxidation",
abstract = "Free-standing, hierarchical, ultrathin, and two-dimensional (2D) polycrystalline Co 3 O 4 flowers were synthesized by a hydrothermal and topotactic transformation process. Aberration-corrected electron microscopy study of both the CoO x precursor structure and the subsequent topotactic transformation processes revealed the nucleation and growth mechanisms of the 2D polycrystalline Co 3 O 4 nanosheets. The free-standing flower-shaped CoO x powders (1-5 μm) consist of numerous self-assembled nanocrystallites (average size ∼1.8 nm). After the topotactic transformation, via a rapid calcination process, the powders maintained their hierarchical flower-like shape, but the CoO x nanocrystallites structurally transformed into ultrathin 2D Co 3 O 4 nanoplates with thicknesses ranging from 1 to 5 nm (average thickness ∼2.4 nm). The final, free-standing, ultrathin 2D polycrystalline Co 3 O 4 flowers possess a BET surface area of 138 m 2 /g. Statistical structural analyses revealed that the exposed surfaces of the Co 3 O 4 flowers are dominated by the Co 3 O 4 {112} (∼70{\%}). The hierarchical Co 3 O 4 flowers contain many grain boundaries, pockets, surface steps, and other types of surface defects. CO oxidation on the as-synthesized hierarchical Co 3 O 4 flowers showed a specific activity (normalized to the surface area) of 0.377 μmol·m -2 ·s -1 , about 5 times that of the most active Co 3 O 4 at 70 °C reported in literature. Furthermore, even under moisture-saturated condition (∼3{\%} H 2 O), the ultrathin 2D Co 3 O 4 catalyst demonstrated a high specific rate and is stable for at least 40 h at 90 and 150 °C. The abundance of accessible coordinatively unsaturated Co 3+ , active oxygen species, and surface defects on the polycrystalline Co 3 O 4 {112} nanosheets are responsible for the experimentally observed high catalytic activity.",
keywords = "catalysis, CO oxidation, Co O, electron microscopy, grain boundaries, two-dimensional materials",
author = "Yafeng Cai and Jia Xu and Yun Guo and Jingyue Liu",
year = "2019",
month = "3",
day = "1",
doi = "10.1021/acscatal.8b04064",
language = "English (US)",
volume = "9",
pages = "2558--2567",
journal = "ACS Catalysis",
issn = "2155-5435",
publisher = "American Chemical Society",
number = "3",

}

TY - JOUR

T1 - Ultrathin, Polycrystalline, Two-Dimensional Co 3 O 4 for Low-Temperature CO Oxidation

AU - Cai, Yafeng

AU - Xu, Jia

AU - Guo, Yun

AU - Liu, Jingyue

PY - 2019/3/1

Y1 - 2019/3/1

N2 - Free-standing, hierarchical, ultrathin, and two-dimensional (2D) polycrystalline Co 3 O 4 flowers were synthesized by a hydrothermal and topotactic transformation process. Aberration-corrected electron microscopy study of both the CoO x precursor structure and the subsequent topotactic transformation processes revealed the nucleation and growth mechanisms of the 2D polycrystalline Co 3 O 4 nanosheets. The free-standing flower-shaped CoO x powders (1-5 μm) consist of numerous self-assembled nanocrystallites (average size ∼1.8 nm). After the topotactic transformation, via a rapid calcination process, the powders maintained their hierarchical flower-like shape, but the CoO x nanocrystallites structurally transformed into ultrathin 2D Co 3 O 4 nanoplates with thicknesses ranging from 1 to 5 nm (average thickness ∼2.4 nm). The final, free-standing, ultrathin 2D polycrystalline Co 3 O 4 flowers possess a BET surface area of 138 m 2 /g. Statistical structural analyses revealed that the exposed surfaces of the Co 3 O 4 flowers are dominated by the Co 3 O 4 {112} (∼70%). The hierarchical Co 3 O 4 flowers contain many grain boundaries, pockets, surface steps, and other types of surface defects. CO oxidation on the as-synthesized hierarchical Co 3 O 4 flowers showed a specific activity (normalized to the surface area) of 0.377 μmol·m -2 ·s -1 , about 5 times that of the most active Co 3 O 4 at 70 °C reported in literature. Furthermore, even under moisture-saturated condition (∼3% H 2 O), the ultrathin 2D Co 3 O 4 catalyst demonstrated a high specific rate and is stable for at least 40 h at 90 and 150 °C. The abundance of accessible coordinatively unsaturated Co 3+ , active oxygen species, and surface defects on the polycrystalline Co 3 O 4 {112} nanosheets are responsible for the experimentally observed high catalytic activity.

AB - Free-standing, hierarchical, ultrathin, and two-dimensional (2D) polycrystalline Co 3 O 4 flowers were synthesized by a hydrothermal and topotactic transformation process. Aberration-corrected electron microscopy study of both the CoO x precursor structure and the subsequent topotactic transformation processes revealed the nucleation and growth mechanisms of the 2D polycrystalline Co 3 O 4 nanosheets. The free-standing flower-shaped CoO x powders (1-5 μm) consist of numerous self-assembled nanocrystallites (average size ∼1.8 nm). After the topotactic transformation, via a rapid calcination process, the powders maintained their hierarchical flower-like shape, but the CoO x nanocrystallites structurally transformed into ultrathin 2D Co 3 O 4 nanoplates with thicknesses ranging from 1 to 5 nm (average thickness ∼2.4 nm). The final, free-standing, ultrathin 2D polycrystalline Co 3 O 4 flowers possess a BET surface area of 138 m 2 /g. Statistical structural analyses revealed that the exposed surfaces of the Co 3 O 4 flowers are dominated by the Co 3 O 4 {112} (∼70%). The hierarchical Co 3 O 4 flowers contain many grain boundaries, pockets, surface steps, and other types of surface defects. CO oxidation on the as-synthesized hierarchical Co 3 O 4 flowers showed a specific activity (normalized to the surface area) of 0.377 μmol·m -2 ·s -1 , about 5 times that of the most active Co 3 O 4 at 70 °C reported in literature. Furthermore, even under moisture-saturated condition (∼3% H 2 O), the ultrathin 2D Co 3 O 4 catalyst demonstrated a high specific rate and is stable for at least 40 h at 90 and 150 °C. The abundance of accessible coordinatively unsaturated Co 3+ , active oxygen species, and surface defects on the polycrystalline Co 3 O 4 {112} nanosheets are responsible for the experimentally observed high catalytic activity.

KW - catalysis

KW - CO oxidation

KW - Co O

KW - electron microscopy

KW - grain boundaries

KW - two-dimensional materials

UR - http://www.scopus.com/inward/record.url?scp=85062338658&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85062338658&partnerID=8YFLogxK

U2 - 10.1021/acscatal.8b04064

DO - 10.1021/acscatal.8b04064

M3 - Article

VL - 9

SP - 2558

EP - 2567

JO - ACS Catalysis

JF - ACS Catalysis

SN - 2155-5435

IS - 3

ER -