Discovering Ultrahigh-Loading of Single-Metal-Atom via Surface Tensile-Strain for Unprecedented Urea Electrolysis

Single-atom-catalysts (SACs) have recently gained significant attention in energy conversion/storage application, while the low-loading amount due to their easy-to-migrate tendency poses a major bottleneck. For energy-saving H2 generation, replacing sluggish oxygen evolution reaction with thermodynamically favorable urea oxidation reaction (UOR) offers a great promise, additionally mitigating the issue of urea-rich water contamination. However, the lack of efficient catalysts to overcome the intrinsically slow kinetics limits its scalable applications. Herein, we discover that incorporating tensile-strain on the surface of Co3O4 (strained-Co3O4; S-Co3O4) support by liquid N2-quenching method can significantly inhibit the migration tendency of Rh single-atom (RhSA), thereby stabilizing ~200% higher-loading of RhSA sites (RhSA-S-Co3O4; bulk loading ~6.6wt%/surface loading ~11.6wt%) compared to pristine-Co3O4 (P-Co3O4). Theoretical calculations revealed a significantly increased migration energy barrier of RhSA on S-Co3O4 surface than P-Co3O4, inhibiting their migration/agglomeration. Surprisingly, the RhSA-S-Co3O4 exhibited exceptional pH-universal UOR-activity, requiring record-low working potentials and surpassing Pt/Rh-C, benefited from superior urea adsorption and stabilization of CO*/NH* intermediates, revealed by DFT simulations. Meanwhile, the assembled urea-electrolyzer delivered 10 mA/cm2 at only 1.33 V with robust stability in alkaline media. This work provides a general methodology towards high-loading SACs for scalable applications.