Synergistic integration of 2D TiN/TiC and Fe single atoms for high-performance and durable oxygen reduction catalysis

Iron-based single-atom (SA) catalysts offer a promising alternative to noble-metal catalysts for the oxygen reduction reaction (ORR), yet their limited intrinsic activity and durability hinder practical energy device applications. Herein, we introduce a novel TiN/TiC-supported Fe SA catalyst (TiNC/Fe–NC) with a hierarchical heterostructure that synergistically enhances Fe–N_x site activity and accessibility. The TiNC/Fe–NC catalyst achieves outstanding ORR performances, with half-wave potentials (E_1/2) of 0.852 V in acidic media and 0.942 V in alkaline media. Theoretical simulations reveal that strong electronic interaction and efficient charge transfer between TiNC and Fe–N_x sites optimize the adsorption energetics of key ORR intermediates, driving the enhanced activity. Remarkably, TiNC effectively scavenges reactive oxygen radicals generated at the Fe centers, ensuring exceptional durability with a minimal 28 mV loss in E_1/2 after 10,000 cycles at 80 °C in acid media. In practical applications, TiNC/Fe–NC delivers peak power densities of 306 mW cm⁻² in zinc-air battery and 732 mW cm⁻² in proton exchange membrane fuel cells, with remarkable long-term stability. This work establishes TiNC/Fe–NC as a high-performance, durable catalyst for advanced energy storage and conversion technologies.