Covalent organic frameworks (COFs) to create new catalytic materials

The oxygen reduction reaction (ORR) is the most important reaction in several life processes, such as biological and cellular respiration, as well as a driving force in energy converting systems such as fuel cells. Therefore, ensuring the reaction is carried out effectively is enormously important for both living tissue and applications such as Proton Exchange Membrane (PEM) fuel cells. That application is of particular importance, as fuel cells become a credible alternative to fossil fuels or energy storage methods such as batteries. It is also important that the molecular oxygen (O2) is abundant in the atmosphere.

But the kinetics of ORR at the cathode of a PEM fuel cell is extremely slow and that hinders the effectiveness of the cell, limiting their usefulness. Speeding up that reaction becomes essential to promote the usability of these systems and this is best achieved using platinum-based catalysts, but is inhibited by the sheer cost of the raw materials. Creating new catalytic materials has become imperative, and of these, covalent organic frameworks with the addition of certain metals within the material to create an electrocatalyst, is the most promising.

These electrocatalysts include noble metals and alloys, carbon materials, quinone and derivatives, transition metal macrocyclic compounds, transition metal chalcogenides, and transition metal carbides. The work by Kamiya has shown that electrocatalysts infused with copper or platinum achieve suitable selectivity – oxygen tolerance. However, the ORR activity of Pt-COF is not as promising. But it does show the excellent methanol tolerance, which is a very attractive property for direct methanol fuel cells.