Understanding the influence of bending on OER activity in metal phthalocyanines: A first-principles study

Carbon-supported nonprecious metals catalysts have been extensively studied and proved effective in electrocatalytic reactions in recent years. In this paper, we systematically investigate the microstructure and electronic properties of metal phthalocyanines (MPc, M = Fe, Co, Ni) supported on single-walled carbon nanotubes (SWCNTs) based on density functional theory (DFT) simulations. The effects of three SWCNTs substrates with different diameters on the catalytic activity are also explored. The results demonstrate that SWCNTs substrate can cause the bending of MPc and the increase of the diameter of the SWCNTs strengthens the adsorption to MPc molecules, which enlarges the N-Metal-N (N-M-N) angles (angels for diagonally opposite nitrogen atoms of metal-N4 coordination sphere) of the MPc structure. Furthermore, the enlargement of the N-M-N angles of MPc can decrease the overpotential of the oxygen evolution reaction (OER), indicating improved catalytic activity. The introduction of SWCNTs substrate improves the conductivity of MPc molecules, and changes the N-M-N angles of MPc, which in turn optimizes the bonding strength between MPc and oxygen-containing intermediates and improves the catalytic activity. Such findings are expected to be employed in more planar molecular complexes catalyzed reactions.