Sequential active-site switches in integrated Cu/Fe-TiO2 for efficient electroreduction from nitrate into ammonia

Understanding the reaction mechanism is critical for efficient electroreduction from NO3- into NH3. Here, a novel sequential active-site-switching (SASS) mechanism is proposed according to the thermodynamic nature of bonding, which involves two key site switches on different active species in an integrated electrocatalyst. We implement this concept by employing Cu/Fe hetero-phase-interface nanoparticles anchored in TiO2 substrate (Cu/Fe-TiO2) as a model platform. Theoretical calculations coupled with in situ infrared spectra confirm the SASS mechanism: the *NO3, preferentially adsorbed on the in-plane Fe phase, switches towards the Cu/Fe hetero-phase interface to reduce into *NH3, and a further switch related to the *NH3 occurs towards the in-plane Cu phase, notably facilitating the NO3--into-NH3 conversion. Such a SASS pathway endows Cu/Fe-TiO2 with excellent intrinsic activity, 4.68- and 2.82-fold higher than that of Cu-TiO2 and Fe-TiO2, respectively.

Automated summary

A novel sequential active-site-switching (SASS) mechanism, based on the thermodynamic nature of bonding, is proposed for efficient electroreduction from NO3- into NH3. Experimental implementation on Cu/Fe-TiO2 shows that the SASS mechanism involves preferential adsorption of *NO3 on the in-plane Fe phase, followed by a switch towards the Cu/Fe hetero-phase interface to reduce into *NH3, and a further switch related to the *NH3 occurs towards the in-plane Cu phase. This SASS pathway endows Cu/Fe-TiO2 with significantly higher intrinsic activity compared to Cu-TiO2 and Fe-TiO2.