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Thermal Transformation of Molecular Ni2+-N-4 Sites for Enhanced CO2 Electroreduction Activity

Title
Thermal Transformation of Molecular Ni2+-N-4 Sites for Enhanced CO2 Electroreduction Activity
Authors
Sa, Young JinJung, HyejinShin, DongyupJeong, Hu YoungRinge, StefanKim, HyungjunHwang, Yun JeongJoo, Sang Hoon
DGIST Authors
Ringe, Stefan
Issue Date
2020-10
Citation
ACS Catalysis, 10(19), 10920-10931
Type
Article
Article Type
Article
Author Keywords
Ni-N/C catalystelectrochemical CO2 reductionheat treatmentlocal structureoxidation state
Keywords
EFFICIENT ELECTROCATALYTIC ACTIVITYELECTROCHEMICAL REDUCTIONCARBON-DIOXIDEORGANIC FRAMEWORKSSELECTIVITYCATALYSTSOXYGEN REDUCTIONSINGLE ATOMSNICKEL SITESMETAL
ISSN
2155-5435
Abstract
Atomically dispersed nickel sites complexed on nitrogen-doped carbon (Ni-N/C) have demonstrated considerable activity for the selective electrochemical carbon dioxide reduction reaction (CO2RR) to CO. However, the high-temperature treatment typically involved during the activation of Ni-N/C catalysts makes the origin of the high activity elusive. In this work, Ni(II) phthalocyanine molecules grafted on carbon nanotube (NiPc/CNT) and heat-treated NiPc/CNT (H-NiPc/CNT) are exploited as model catalysts to investigate the impact of thermal activation on the structure of active sites and CO2RR activity. H-NiPc/CNT exhibits a ∼4.7-fold higher turnover frequency for CO2RR to CO in comparison to NiPc/CNT. Extended X-ray absorption fine structure analysis and density functional theory (DFT) calculations reveal that the heat treatment transforms the molecular Ni2+-N4 sites of NiPc into Ni+-N3V (V: vacancy) and Ni+-N3 sites incorporated in the graphene lattice that concomitantly involves breakage of Ni-N bonding, shrinkage in the Ni-N-C local structure, and decrease in the oxidation state of the Ni center from +2 to +1. DFT calculations combined with microkinetic modeling suggest that the Ni-N3V site appears to be responsible for the high CO2RR activity because of its lower barrier for the formation of *COOH intermediate and optimum *CO binding energy. In situ/operando X-ray absorption spectroscopy analyses further corroborate the importance of reduced Ni+ species in boosting the CO2RR activity. Copyright © 2020 American Chemical Society.
URI
http://hdl.handle.net/20.500.11750/12815
DOI
10.1021/acscatal.0c02325
Publisher
American Chemical Society
Related Researcher
  • Author Ringe, Stefan Ab initio multi-scale engineering Lab(AIMS-E Lab)
  • Research Interests Energy conversion and electrocatalysis; CO₂ reduction; fuel cells; energy storage; batteries; capacitors; electrified and solvated interfaces
Files:
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Collection:
Department of Energy Science and EngineeringAb initio multi-scale engineering Lab(AIMS-E Lab)1. Journal Articles


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