TY - JOUR
T1 - Methane to Methanol Conversion over N-Doped Graphene Facilitated by Electrochemical Oxygen Evolution
T2 - A First-Principles Study
AU - Hsieh, Chi Tien
AU - Tang, Yu Tzu
AU - Ho, Yeu Shiuan
AU - Shao, Wei Kai
AU - Cheng, Mu Jeng
N1 - Funding Information:
We acknowledge financial support from the Ministry of Science and Technology of the Republic of China under grant no. MOST 111-2113-M-006-010-MY3 and the National Center for High-Performance Computing (NCHC) of the National Applied Research Laboratories (NARLabs) of Taiwan for providing computational resources.
Publisher Copyright:
© 2022 American Chemical Society.
PY - 2023/1/12
Y1 - 2023/1/12
N2 - Direct methane oxidation to methanol is ideal for replacing the oxygen evolution reaction (OER) in artificial photosynthesis. This reaction requires less electricity and generates more valuable products than the OER. Moreover, it provides a better way to utilize abundant but inert methane. In this study, we have used density functional theory combined with a constant electrode potential model to evaluate the possibility of using abundant and low-cost N-doped graphene to catalyze this reaction. The active oxygen (*O) for rate-determining C-H activation is generated during the OER process. The results from our calculations show that this catalysis could be realized when graphene is doped with two nitrogen atoms in the vicinity of the reaction center so that long-lived *O is present and reacts to break strong methane C-H bonds. The minimum overall kinetic barrier is 0.91 eV at a potential of U = 1.10 VSHE, which is 0.82 eV lower than that in the absence of Us. The significant barrier reduction indicates that anodic potentials play essential roles in increasing the reactivity of N-doped graphene. During C-H activation, hydrogen is transferred from methane to *O. Analyzing this step using the Intrinsic Atomic Orbitals approach, we find that it follows a hydrogen atom transfer mechanism where the proton and electron travel together. Importantly, our analysis reveals that this transfer starts with the excitation of one electron from the *O lone pair to a surface π-orbital. This excitation increases the radical character on *O, rendering it reactive to couple with the transferred hydrogen atom. Easing this excitation is expected to further improve the reactivity of *O, as demonstrated by our calculations.
AB - Direct methane oxidation to methanol is ideal for replacing the oxygen evolution reaction (OER) in artificial photosynthesis. This reaction requires less electricity and generates more valuable products than the OER. Moreover, it provides a better way to utilize abundant but inert methane. In this study, we have used density functional theory combined with a constant electrode potential model to evaluate the possibility of using abundant and low-cost N-doped graphene to catalyze this reaction. The active oxygen (*O) for rate-determining C-H activation is generated during the OER process. The results from our calculations show that this catalysis could be realized when graphene is doped with two nitrogen atoms in the vicinity of the reaction center so that long-lived *O is present and reacts to break strong methane C-H bonds. The minimum overall kinetic barrier is 0.91 eV at a potential of U = 1.10 VSHE, which is 0.82 eV lower than that in the absence of Us. The significant barrier reduction indicates that anodic potentials play essential roles in increasing the reactivity of N-doped graphene. During C-H activation, hydrogen is transferred from methane to *O. Analyzing this step using the Intrinsic Atomic Orbitals approach, we find that it follows a hydrogen atom transfer mechanism where the proton and electron travel together. Importantly, our analysis reveals that this transfer starts with the excitation of one electron from the *O lone pair to a surface π-orbital. This excitation increases the radical character on *O, rendering it reactive to couple with the transferred hydrogen atom. Easing this excitation is expected to further improve the reactivity of *O, as demonstrated by our calculations.
UR - http://www.scopus.com/inward/record.url?scp=85145327473&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85145327473&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.2c07736
DO - 10.1021/acs.jpcc.2c07736
M3 - Article
AN - SCOPUS:85145327473
SN - 1932-7447
VL - 127
SP - 308
EP - 318
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 1
ER -