Mechanism Study of CH4 Decomposition on Carbon Black-Loaded Activated Carbon by DFT Calculation

Abstract

Carbon black-loaded activated carbon (CB-loaded AC) is a cost-effective catalyst for CH₄ decomposition to produce H₂. CB induces defects on the AC surface, enhancing catalytic activity. Current studies on the role of defects in promoting CH₄ decomposition are primarily experimental, with unclear mechanisms. Hence, exploring the reaction mechanism of defects in CH₄ decomposition is crucial. In this work, the Grand Canonical Monte Carlo (GCMC) and Density Functional Theory (DFT) are used to construct defects (Mono-Vacancy defect, Di-Vacancy defect, and Stone-Wales defect) on the AC surface, determining the catalytic mechanism of defects in CH₄ decomposition. The results show that during the CH₄ decomposition (C─H bond cleavage) phase, defective AC reduces the energy barriers for CH₄ decomposition. Under identical conditions, the rate-determining step of C─H bond cleavage in CH₄ occurs more readily on AC with Mono-Vacancy, Di-Vacancy, and Stone-Wales defects, with corresponding reductions in energy barriers of 4.64, 2.36, and 3.12%, respectively. The total energy barriers for the reaction are reduced by 12.95, 27.58, and 8.43%, respectively. This indicates that the defects significantly lower the energy barrier for CH₄ decomposition, thereby facilitating the reaction and confirming that these defects act as active sites for the catalytic decomposition of CH₄ on AC.