Metal-Free Materials for Electrocatalytic Oxygen Evolution Reaction: Status and Prospects

The oxygen evolution reaction (OER) is essential to the operation of various renewable energy technologies, particularly in water electrolysis and fuel cells. Nevertheless, the broad application of benchmark materials derived from iridium (Ir) and ruthenium (Ru) is seriously hindered by their scarcity. Owing to their abundance, sustainability, and tunable properties, metal-free materials have been regarded as potential alternative options to traditional metal-based electrocatalysts for OER. This review comprehensively overviews recent advancements in metal-free materials for electrocatalytic OER, focusing on their design strategies, catalytic mechanisms, and performance evaluation. Different types of metal-free OER catalysts, including carbon-based materials, carbon nitrides, and organic materials are discussed in detail. Additionally, recent progress in understanding the structure-activity relationships and approaches to enhancing their catalytic performance is highlighted. Finally, the challenges and future prospects in the realm of metal-free OER catalysts are critically presented, providing valuable insights into potential directions for future research endeavors.