Fluorinated catalysts for the oxygen evolution reaction: a comprehensive review of synthesis, structure, and performance

Abstract

Electrochemical water splitting is considered one of the most viable, effective, and environmentally friendly approaches for renewable energy conversion and storage. Nevertheless, due to its slow reaction kinetics, the oxygen evolution reaction (OER) at the anode remains a significant challenge. Researchers have discovered that incorporating fluorine into catalysts in the past few years can significantly improve their OER performance. This enhancement is attributed to fluorine's unique characteristic of possessing the highest electronegativity among all the elements. Consequently, fluorine forms highly ionic metal–fluorine bonds, which promote the electrocatalytic reactions necessary for the OER. This approach has led to considerable advancements in catalyst development for OER applications. This review encompasses various types of state-of-the-art fluorinated catalysts, including binary, ternary, and high-entropy transition-metal fluorides, oxyfluorides, fluorinated versions of oxides, (oxy)hydroxides, carbonate hydroxides, carbides, nitrides, phosphides, sulfides, and carbons. Research has shown that fluorine-containing catalysts demonstrate exceptional performance in the OER, with some outperforming industry standards such as IrO2 or RuO2. Incorporating fluorine through doping has emerged as a successful approach to enhance the OER performance of catalysts, significantly decreasing the overpotential and Tafel slope while improving durability. The data indicate that fluorination leads to an average reduction of 21.6% in overpotential and 29.6% in the Tafel slope. When a new OER catalyst is developed, improving its OER performance through fluorination might be worth exploring if this has not been done. The OER performances of these catalysts are closely linked to their synthesis methods and structural characteristics.