Journal
ACS SUSTAINABLE CHEMISTRY & ENGINEERING
Volume 9, Issue 18, Pages 6438-6445Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acssuschemeng.1c01364
Keywords
Single-atom catalysts; N/C coordination numbers; XANES spectra; DFT calculation; CO2 reduction reaction
Categories
Funding
- National Natural Science Foundation-China [51676171]
- Zhejiang Provincial Key Research and Development Program-China [2020C01135]
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Atomically dispersed Ni-based catalysts with various N/C coordination numbers were fabricated, with the Ni@NxCy-1000 catalyst achieving the highest CO selectivity at a specific temperature. Density functional theory calculation revealed that the active Ni-N2C2 sites played a crucial role in enhancing the CO2RR catalytic activity.
Atomically dispersed Ni-N-C is known as an efficiently active site for the CO2 reduction reaction (CO2RR). However, the effect of the coordination environment between the Ni-N and Ni-C sites on catalytic activity has still not been studied systematically. Herein, atomically dispersed Ni-based catalysts with various N/C coordination numbers (named Ni@NxCy) were fabricated with cost-effective carbon substrates. EXAFS fitting analysis confirmed that the N coordination number decreased from 4 to 1 in Ni@NxCy, catalysts when the pyrolysis temperature increased from 800 to 1100 degrees C, whereas the C coordination number showed an opposite trend. The Ni@NxCy-1000 catalyst with the optimum coordination numbers of two N and two C atoms pyrolyzed at 1000 degrees C achieved the highest FEco of 98.7% at a potential of -0.7 V vs RHE. The density functional theory (DFT) calculation clarified that Ni-N2C2 active sites were favorable to generate more unoccupied Ni 3d orbitals to decrease the free energy (to +0.80 eV) of the rate-determining step, so as to dramatically increase CO2RR catalytic activity.
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