Theoretical\nScreening of Highly Efficient Single-Atom\nCatalysts Based on Covalent Triazine Frameworks for Oxygen Reduction

Abstract

Covalent triazine frameworks (CTFs) obtained from the\ntrimerization\nof aromatic nitriles are expected to be the preferred carrier for\nsingle-atom catalysts (SACs). Using density functional theory methods,\nthe oxygen reduction reaction (ORR) performance of a series of 3d,\n4d, and 5d transition metals supported on the 6N or 9N pore of the\nCTF system [M-CTF(6N) or M-CTF(9N)] is explored. At first, 32 kinds\nof M-CTF(6N) and M-CTF(9N) are screened out with high thermodynamic\nand electrochemical stability. The binding energy of ORR intermediates\nand the change of Gibbs free energy in each step of the ORR are calculated.\nThe overpotential of Pd-CTF(6N) is the lowest, which is 0.38 V. Considering\nthat the ORR activity of M-CTFs is mainly limited by the strong binding\nof *OH, M-CTF(6N) and M-CTF(9N) are further modified by the OH ligand,\nnamely, M-OH-CTF(6N) and M-OH-CTF(9N). After being modified by the\nOH ligand, due to the weakened binding strength of *OH, all these\nscreened M-CTFs exhibit better ORR activity. Among them, the <i>η</i> values of Cu-OH-CTF(6N), Pd-OH-CTF(6N), Rh-OH-CTF(6N),\nIr-OH-CTF(6N), Rh-OH-CTF(9N), and Ir-OH-CTF(9N) are 0.39, 0.38, 0.24,\n0.30, 0.31, and 0.33 V, respectively, which possess better ORR activity\nthan the Pt(111) surface (<i>η</i> = 0.45 V). This\nwork highlights the great potential of CTFs as an efficient carrier\nfor SACs.