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

Exploring single-atom catalysts (SACs) for the nitrate reduction reaction (NO3–; NitRR) to value-added ammonia (NH3) offers a sustainable alternative to both the Haber–Bosch process and NO3–-rich wastewater treatment. However, due to the insufficient electron deficiency and unfavorable electronic structure of SACs, resulting in poor NO3–-adsorption, sluggish proton (H*) transfer kinetics, and preferred hydrogen evolution, their NO3–-to-NH3selectivity and yield rate are far from satisfactory. Herein, a systematic theoretical prediction reveals that the local electron deficiency of an f-block Gd single atom (GdSA) can be significantly regulated upon coordination with oxygen-defect-rich NiO (GdSA-D-NiO400) support. Thus, facilitating stronger NO3–adsorption viastrong Gd5d–O2porbital 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 NH3selectivity/yield rate. Motivated by DFT prediction, we delicately stabilized electron-deficient (strongly electrophilic) GdSAon D-NiO400(∼84% strong electrophilic sites), which exhibited excellent alkaline NitRR activity (NH3Faradaic efficiency ∼97% and yield rate ∼628 μg/(mgcath)) along with superior structural stability, as revealed by in situRaman spectroscopy, significantly outperforming weakly electrophilic Gd nanoparticles, defect-free GdSA-P-NiO400, and reported state-of-the-art catalysts.