Dual-effect electrocatalyst: activating interfacial water and optimizing adsorption energy on adjacent Fe3C/FeN4 sites for enhanced oxygen reduction reaction

Constructed a Fe 3 C nanoparticle/Fe single-atom composite catalyst and elucidated its proton-feeding mechanism. • Clarified the role of interfacial water and proposed a novel catalyst design strategy. • Synergy of mesopore-rich substrate and electronic modulation boosts intrinsic activity. • Fe 3 C@Fe/NC exhibits outstanding electrochemical performance and stability. The oxygen reduction reaction (ORR) is crucial for sustainable power generation, yet its sluggish kinetics, mainly caused by insufficient proton supply and excessive intermediates adsorption, severely limit the overall efficiency. An important ongoing challenge is to regulate both factors to significantly enhance ORR. Herein, a dual-effect catalyst, Fe 3 C@Fe/NC, was designed and synthesized via a systematic two-step Fe 3+ doping strategy to achieve closely adjacent multiple active sites. This catalyst features activated interfacial water to provide sufficient protons and optimized intermediate adsorption energy. Structural characterization revealed uniformly distributed FeN 4 sites alongside adjacent Fe 3 C nanoparticles interwoven by carbon nanotubes. In-situ spectroscopic techniques and theoretical calculations demonstrated that Fe 3 C nanoparticles can activate interfacial water, enhancing dynamic active hydrogen donation to neighboring FeN 4 sites, thereby accelerating the proton-coupled electron transfer (PCET) kinetics. Simultaneously, the regulated electronic structure around FeN 4 sites offers appropriate intermediate adsorption energy, further boosting ORR activity and durability. The Fe 3 C@Fe/NC catalyst exhibits a remarkable half-wave potential of 0.904 V, a higher power density of 221.3 mW cm −2 and excellent durability with 1250 h operation at 5 mA cm −2 in zinc-air battery test. This work establishes a proximal proton-donation strategy to overcome the alkaline ORR bottleneck. The Fe 3 C sites not only modulate the local microenvironment of the FeN 4 sites, more importantly, in-situ infrared spectroscopy and theoretical calculations reveal that the Fe 3 C sites can activate interfacial water and promote water dissociation, thereby supplying protons to the FeN 4 sites to accelerate the proton-coupled electron transfer process. Download: Download high-res image (52KB) Download: Download full-size image