Bidirectional electron donation in Cu₁-Ti pairs on TiO_x for efficient nitric oxide electroreduction

Electrocatalytic nitric oxide reduction (NORR) enables the efficient abatement of NO while simultaneously synthesizing valuable ammonia (NH₃). However, the strong polarity of NO hinders its effective activation on conventional NORR catalysts because of their single-site interaction mode, wherein either the nitrogen (N) or oxygen (O) atom of NO binds to the catalyst through a unidirectional electron transfer. In this study, we construct dual-atom Cu₁-Ti pairs on the titanium oxide (TiO_x) substrate by using the complementary affinities of Ti for nitrogen and Cu for oxygen, which simultaneously activates both ends of the N=O bond. The designed Cu₁-Ti pairs achieve competitive NORR performance with an NH₃ yield of 189.9 μmol h^-1 cm^-2 and a Faradaic efficiency of 93.7%. In situ techniques and theoretical calculations demonstrate that this dual-atom configuration shifts the mechanism from an end-on adsorption pathway observed on homonuclear pairs to a fully activating side-on mode. By highlighting the importance of adapted active site design in the electrocatalytic activation of polar molecules, this study facilitates the development of next-generation catalysts for complex transformations.