Dithiine Bridged Phthalocyanine-Based Covalent Organic Frameworks for Highly Efficient Oxygen Reduction Reaction

The rational regulation of oxygen reduction catalytic activity of transition metal/nitrogen-doped carbon (M-N-C) is of great significance for sustainable energy conversion devices. Here, we designed a series of dithiine bridged phthalocyanine-based covalent organic frameworks (denoted as COFDTI) and studied the effect of the introduction of dithiine on the performance of oxygen reduction by density functional theory. The results demonstrate that the dithiine in covalent framework lowers the d-band center in metal atoms toward a more negative level relative to the Fermi level and weakens their adsorption strength with oxygen-containing intermediates owing to the electron-withdrawing effect of dithiine compared with counterparts without S atoms in the skeleton, i.e., COFBTC, which causes the catalytic activities of COFDTI-Fe to shift from the left branch of volcano plot to the apex and exceed that of Pt (111). This work not only seeks a promising candidate for oxygen reduction reaction but also provides a new view for designing efficient and stable cathode materials by directly introducing electron-withdrawing functionality in the M-N-C electrocatalysts.