The action mechanisms and structures designs of F-containing functional materials for high performance oxygen electrocatalysis

Non-renewable fossil fuels have led to serious problems such as global warming, environmental pollution, etc. Oxygen electrocatalysis including oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) plays a central role in clean energy conversion, enabling a number of sustainable processes for future air battery technologies. Fluorine, as the most electronegative element (4.0) not only can induce more efficient regulation for the electronic structure, but also can bring more abundant defects and other novel effects in materials selection and preparation for favorable catalysis with respect to the other non-metal elements. However, an individual and comprehensive overview of fluorine-containing functional materials for oxygen electrocatalysis field is still blank. Therefore, it is very meaningful to review the recent progresses of fluorine-containing oxygen electrocatalysts. In this review, we first systematically summarize the controllable preparation methods and their possible development directions based on fluorine-containing materials from four preparation methods. Due to the strong electron-withdrawing properties of fluorine, its control of the electronic structure can effectively enhance the oxygen electrocatalytic activity of the materials. In addition, the catalytic enhancement effect of fluorine on carbon-based materials also includes the prevent oxidation and the layer peeling, and realizes the precise atomic control. And the catalytic improvement mechanism of fluorine containing metal-based compounds also includes the hydration of metal site, the crystal transformation, and the oxygen vacancy induction. Then, based on their various dimensions (0D–3D), we also have summarized the advantages of different morphologies on oxygen electrocatalytic performances. Finally, the prospects and possible future researching direction of F-containing oxygen electrocatalysts are presented (e.g., novel pathways, advanced methods for measurement and simulation, field assistance and multi-functions). The review is considered valuable and helpful in exploring the novel designs and mechanism analyses of advanced fluorine-containing electrocatalysts.