Core Level Shifts of Hydrogenated Pyridinic and Pyrrolic Nitrogen in the Nitrogen-Containing Graphene-Based Electrocatalysts: In-Plane vs Edge Defects

Journal Article · Wed Dec 07 04:00:00 EST 2016 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/acs.jpcc.6b09778· OSTI ID:1369185

Matanovic, Ivana ^[1]; Artyushkova, Kateryna ^[2]; Strand, Matthew B. ^[3]; Dzara, Michael J. ^[3]; Pylypenko, Svitlana ^[3]; Atanassov, Plamen ^[2]

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1. Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Chemical and Biological Engineering; Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Chemical and Biological Engineering
3. Colorado School of Mines, Golden, CO (United States). Dept. of Chemistry

A combination of N 1s X-ray photoelectron spectroscopy (XPS) and first principles calculations of nitrogen-containing model electrocatalysts was used to elucidate the nature of the nitrogen defects that contribute to the binding energy (BE) range of the N 1s XPS spectra of these materials above ~400 eV. Experimental core level shifts were obtained for a set of model materials, namely N-doped carbon nanospheres, Fe–N–carbon nanospheres, polypyrrole, polypyridine, and pyridinium chloride, and were compared to the shifts calculated using density functional theory. The results confirm that the broad peak positioned at ~400.7 eV in the N 1s XPS spectra of N-containing catalysts, which is typically assigned to pyrrolic nitrogen, contains contributions from other hydrogenated nitrogen species such as hydrogenated pyridinic functionalities. Namely, N 1s BEs of hydrogenated pyridinic-N and pyrrolic-N were calculated as 400.6 and 400.7 eV, respectively, using the Perdew–Burke–Ernzerhof exchange-correlation functional. A special emphasis was placed on the study of the differences in the XPS imprint of N-containing defects that are situated in the plane and on the edges of the graphene sheet. Density functional theory calculations for BEs of the N 1s of in-plane and edge defects show that hydrogenated N defects are more sensitive to the change in the chemical environment in the carbon matrix than the non-hydrogenated N defects. In conclusion, calculations also show that edge-hydrogenated pyridinic-N and pyrrolic-N defects only contribute to the N 1s XPS peak located at ~400.7 eV if the graphene edges are oxygenated or terminated with bare carbon atoms.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: Colorado School of Mines, Golden, CO (United States). Univ. of New Mexico, Albuquerque, NM (United States). Center for Microengineered materials
• Grant/Contract Number: AC52-06NA25396
• OSTI ID: 1369185
• Report Number(s): LA-UR--16-27267
• Journal Information: Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 51 Vol. 120; ISSN 1932-7447
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

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