Tailoring metal-support interaction over faceted TiO₂ and copper nanoparticles for electrocatalytic nitrate reduction to ammonia

The electrocatalytic nitrate reduction reaction (NO₃⁻RR) provides a sustainable route for ammonia production while mitigating nitrate pollutants in the environment. Metal-support interaction has a significant influence on this electrocatalytic process. However, the mechanism of the facet-dependent metal-support interaction in the NO₃⁻RR is still unknown. Herein, we report the modulation of the metal-support interaction by depositing copper nanoparticles on anatase TiO₂ with different facet exposures, i.e., (001) and (101) facets. The result of copper nanoparticles being deposited on TiO₂ with dominant (101) facet exposure is an enhanced ammonia yield rate of 447.5 μg mg_cat⁻¹ h⁻¹ at −0.9 V vs. reversible hydrogen electrode (RHE), which is 4.2 times higher than the pristine TiO₂ counterpart. The strong interaction between copper nanoparticles and TiO₂ with dominant (101) facet exposure contributes to a greater increase in catalytic performance than TiO₂ with dominant (001) facet exposure. The strong interaction leads to electron-deficient copper nanoparticles, efficient electron transfer, and stronger binding of the *NO₂ intermediate, promoting the hydrogenation process in the NO₃⁻ reduction reaction for selective NH₃ synthesis.