Defect‐Enhanced CO2 Reduction Catalytic Performance in O‐Terminated MXenes

Electrochemical carbon dioxide reduction reaction (CO2RR) represents a promising way to generate fuels and chemical feedstock sustainably. Recently, studies have shown that two‐dimensional metal carbides and nitrides (MXenes) can be promising CO2RR electrocatalysts due to the alternating −C and −H c...

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Bibliographic Details
Published in:ChemSusChem 2020-11, Vol.13 (21), p.5690-5698
Main Authors: Chen, Hetian, Handoko, Albertus D., Wang, Tianshuai, Qu, Jiale, Xiao, Jiewen, Liu, Xiaopeng, Legut, Dominik, Wei Seh, Zhi, Zhang, Qianfan
Format: Article
Language:English
Subjects:
2D materials
Carbon dioxide
Catalysts
Chemical reduction
CO2 reduction reaction
defect engineering
Electrocatalysts
Electronic structure
Fermi level
first-principles simulations
Metal carbides
MXenes
Structural analysis
Surface structure
Transition metals
Vacancies
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Summary:Electrochemical carbon dioxide reduction reaction (CO2RR) represents a promising way to generate fuels and chemical feedstock sustainably. Recently, studies have shown that two‐dimensional metal carbides and nitrides (MXenes) can be promising CO2RR electrocatalysts due to the alternating −C and −H coordination with intermediates that decouples scaling relations seen on transition metal catalysts. However, further by tuning the electronic and surface structure of MXenes it should still be possible to reach higher turnover number and selectivities. To this end, defect engineering of MXenes for electrochemical CO2RR has not been investigated to date. In this work, first‐principles modelling simulations are employed to systematically investigate CO2RR on M2XO2‐type MXenes with transition metal and carbon/nitrogen vacancies. We found that the −C‐coordinated intermediates take the form of fragments (e. g., *COOH, *CHO) whereas the −H‐coordinated intermediates form a complete molecule (e. g., *HCOOH, *H2CO). Interestingly, the fragment‐type intermediates become more strongly bound when transition‐metal vacancies are present on most MXenes, while the molecule‐type intermediates are largely unaffected, allowing the CO2RR overpotential to be tuned. The most promising defective MXene is Hf2NO2 containing Hf vacancies, with a low overpotential of 0.45 V. More importantly, through electronic structure analysis it could be observed that the Fermi level of the MXene changes significantly in the presence of vacancies, indicating that the Fermi level shift can be used as an ideal descriptor to rapidly predict the catalytic performance of defective MXenes. Such an evaluation strategy is applicable to other catalysts beyond MXenes, which could enhance high throughput screening efforts for accelerated catalyst discovery. Enhancing catalytic performance through vacancies: Vacancies influence the binding energy of intermediates and further affect the limiting potential of the electrochemical carbon dioxide reduction reaction. The catalytic performance of MXenes can be enhanced by introducing a suitable defect type. Furthermore, the shift of Fermi level can be a simple yet promising descriptor to predict the effect exerted by vacancies.
ISSN:1864-5631
1864-564X
DOI:10.1002/cssc.202001624