Atomically Dispersed Zn and Ir Synergistic Modulation of Substrate and Active Sites for High-Performance Ammonia Oxidation

A rationally designed, bifunctional ammonia-oxidation catalyst spatially decouples NH₃ activation and *OH adsorption to overcome the intrinsic trade-off of single-component systems. Atomically dispersed Zn single atoms in an N,O-doped carbon support (Zn₁/NOC) serve as dedicated *OH-adsorption sites, while Ir-modulated Pt(100) nanocubes selectively activate NH₃. Comprehensive structural characterization (AC HAADF-STEM, XPS, XANES, EXAFS) confirms Zn-N₃O₃ coordination and atomically isolated Zn centers. Electrochemical-kinetic analysis, mechanistic spectroscopy, and DFT calculations reveal that Zn₁/NOC lowers the *OH-adsorption energy by 0.84 eV (to −0.98 eV versus −0.14 eV on Pt), facilitating the dehydrogenation steps and reducing surface poisoning. Simultaneously, traces of stabilized Ir⁴⁺-decorated Pt cubes enhance NH₃ dissociation kinetics to form N₂. The catalyst demonstrates a specific activity of 3.80 mA cm⁻²_PGMs, exceeding the state-of-the-art benchmarks. When deployed in a membrane-electrode-assembly direct ammonia fuel cell, the catalyst achieves a maximum current density of 200 mA cm⁻² and a peak power density of 18 mW cm⁻², representing a significant improvement over previously reported systems, with ∼250% increase over Pt_np–C || Pt/C and more than double monofunctional systems. This work demonstrates a generalizable strategy for engineering spatially decoupled active sites in multistep electrochemical reactions, paving the way for high-performance ammonia fuel cells and beyond.