“…11 Density functional theory (DFT) calculations on CH 4 activation have been performed primarily on TM-based catalysts, 12 mostly TM surfaces rather than finite-size particles. 13–15 Among them, 3d TMs (TM = Fe, 16,17 Co, 18–20 Ni, 21,22 Cu, 23,24 etc. ) have gained particular attention due to their catalytic activity and low-cost compared with noble metals, e.g.…”