Plasmon-induced photocatalytic nitrogen fixation on medium-spin Au3Fe1/Mo single-atom alloy antenna reactor

Developing photocatalysts with active sites that have appropriate interactions with both N₂ and reactive intermediates has proved to be feasible for direct nitrogen reduction but is still a formidable challenge. Herein, a medium-spin Au₃Fe₁/Mo single-atom alloy photocatalyst with optical antenna structure is fabricated through an alloying strategy. Fe atoms of a medium-spin state anchored on Au nanoparticles at the single-atom level via Au–Fe bonding is confirmed by combined characterizations of aberration-corrected high-angle annular dark field scanning transmission electron microscopy (AC-HAADF-STEM), X-ray absorption fine structure (XAFS), and Mössbauer spectroscopic techniques. With strong Mo-Fe-Au electronic interactions, the Fe sites act as intrinsic centers apt for nitrogen adsorption and activation, which is conducive to the preferential cleavage of the N≡N bond and modulate adsorption of reactive intermediates. Due to synergistic effect of Au nanoparticles acting as optical antennae, the Au₃Fe₁/Mo photocatalyst showed excellent photocatalytic nitrogen reduction reaction (pNRR) performance, giving an ammonia formation rate of 484.2 μmol h⁻¹ g⁻¹ and solar-to-ammonia (STA) conversion efficiency up to 0.12%.