Frustrated Lewis Pairs on Zr Single Atoms Supported N-Doped TiO_2-x Catalysts for Electrochemical Nitrate Reduction To Ammonia

The electrochemical reduction of nitrates (NO3RR) for ammonia synthesis at room temperature holds immense potential. One key challenge is the adsorption and activation of NO3-, along with the provision of sufficient active hydrogen to accelerate the hydrogenation process. Here, the study prepares N-doped TiO2-x supported by Zr single atoms (Zr-TiON) with rich oxygen vacancies (Ov), in which unsaturated Zr (Lewis acidic, LA) sites together with oxygen atoms around Ov (Lewis base, LB) form frustrated Lewis acid-base pairs (FLPs). At -60 mA cm(-2), NH3 Faradaic efficiency reaches 94.8%, corresponding to the production rate of 663.15 mu mol h-1 mgcat-1. The yield rate is up to 26.16 mmol h(-1)mg(cat)(-1) at -1 A cm(-2) in flowing electrolyzer. Theoretical calculations and in situ spectroscopy analysis reveal that the interaction between LA and LB sites in FLPs plays a crucial role in facilitating adsorption and activation of electron-rich NO3- and electron-deficient *H. The presence of enhanced FLPs significantly reduces the energy barrier for H2O dissociation, lowering it to 0.20 eV, which facilitates subsequent hydrogenation reactions. The abundance of *H accelerates hydrogenation process, thereby enhancing the activity of NO3RR. This FLP design offers a promising approach for paving the way for the development of highly efficient NO3RR catalysts.