Efficient Nitrate Conversion to Ammonia on f-Block Single-Atom/Metal Oxide Heterostructure Local Electron-Deficiency Modulation.

Exploring single-atom catalysts (SACs) for the nitrate reduction reaction (NO; NitRR) to value-added ammonia (NH) offers a sustainable alternative to both the Haber-Bosch process and NO-rich wastewater treatment. However, due to the insufficient electron deficiency and unfavorable electronic structure of SACs, resulting in poor NO-adsorption, sluggish proton (H*) transfer kinetics, and preferred hydrogen evolution, their NO-to-NH selectivity and yield rate are far from satisfactory. Herein, a systematic theoretical prediction reveals that the local electron deficiency of an -block Gd single atom (Gd) can be significantly regulated upon coordination with oxygen-defect-rich NiO (Gd-D-NiO) support. Thus, facilitating stronger NO adsorption strong Gd-O orbital coupling and further improving the protonation kinetics of adsorption intermediates by rapid H* capture from water dissociation catalyzed by the adjacent oxygen vacancy site along with suppressed H* dimerization synergistically boosts the NH selectivity/yield rate. Motivated by DFT prediction, we delicately stabilized electron-deficient (strongly electrophilic) Gd on D-NiO (∼84% strong electrophilic sites), which exhibited excellent alkaline NitRR activity (NH Faradaic efficiency ∼97% and yield rate ∼628 μg/(mg h)) along with superior structural stability, as revealed by Raman spectroscopy, significantly outperforming weakly electrophilic Gd nanoparticles, defect-free Gd-P-NiO, and reported state-of-the-art catalysts.