Reza Pamungkas Putra Sukanli, Muhammad Haris Mahyuddin, Adhitya Gandaryus Saputro, Mohammad Kemal Agusta, Hadi Teguh Yudistira, Kazunari Yoshizawa, Hermawan Kresno Dipojono
Graphene-based single-atom catalysts have attracted increasing interest due to their potential to catalyze the direct conversion of CH4 to CH3OH. In particular, the porphyrin-like FeN4 complex has recently been reported to convert CH4 to CH3OH at low temperatures with high selectivity. However, only N2O and H2O2, which are high-cost and scarce compared to O2, can be used as the oxidant of the reaction. In this paper, we perform density functional theory calculations on graphitic MN4G-BN (M = Fe, Co, Cu) and CuN4G-PN systems to evaluate the CH4 oxidation to CH3OH using O2. We found that the addition of B doping adjacent to the Fe and Co centers as well as P doing adjacent to the Cu center facilitates a facile O═O bond dissociation with an activation barrier of less than 0.4 eV, resulting in active M-O and inactive B/P-O sites. This low barrier is due to the early O═O bond elongation at the O2 adsorption step and the stability of the atomically adsorbed O atoms. In the subsequent CH4 oxidation, the resultant OCuN4G-OPN is found to be significantly more CH4-reactive than the OFeN4G-OBN and OCoN4G-OBN with a H-CH3 activation barrier of only 0.66 eV. Such high reactivity is due to the proximity of the electron-acceptor orbital (i.e., the Cu-O lowest unoccupied molecular orbital) toward the Fermi level. Moreover, the CH4 oxidation on CuN4G-PN is predicted to form CH3OH with high exothermicity and high resistance to overoxidation. This study suggests a high possibility for CuN4G-PN as a potential catalyst for the stepwise conversion of CH4 to CH3OH using O2 at low temperatures. © 2023 The Authors. Published by American Chemical Society.
Research Group of Advanced Functional Materials, Faculty of Industrial Technology, Institut Teknologi Bandung, Bandung, 40132, Indonesia; Research Center for Nanoscience and Nanotechnology, Institut Teknologi Bandung, Bandung, 40132, Indonesia; Mechanical Engineering Study Program, Institut Teknologi Sumatera, South Lampung, Way Hui, 35365, Indonesia; Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka, 819-0395, Japan
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