Covalent Organic Frameworks-Based Nanomaterials for Oxygen Reduction Reactions

Because of the high price and low abundance of Pt-based electrocatalysts, there is a great demand for alternative electrocatalysts for the oxygen reduction reaction (ORR) that pushes the widespread application of metal-air batteries and proton exchange membrane fuel cells. Covalent organic frameworks (COFs) have recently been revealed as promising electrocatalysts for the ORR due to their predesignate structures that allow (i) the arrangement of active centers with atomic precision, (ii) the tuning of nanopores size, (iii) the increase of the accessible surface area and (iv) the exposure to abundant electrocatalytic active sites. In this chapter, we present an overview of the recent advances in the field of oxygen reduction electrocatalysis utilizing COF-based catalysts. Selected recent examples of the different strategies developed for the use of COFs as electrocatalysts have been classified attending to the need for pyrolytic steps and the presence or absence of metallic centers. The advantages and limitations of the different families of COFs are critically presented and we specially highlight the interest to produce non-metallated pyrolysis-free COF-based electrocatalysts as the most promising strategy for the development of efficient environmentally friendly electrocatalysts for the oxygen reduction reaction.