Tandem Electrocatalytic Nitrate Reduction to Ammonia on MBenes

We demonstrate the great feasibility of MBenes as a new class of tandem catalysts for electrocatalytic nitrate reduction to ammonia (NO₃ RR). As a proof of concept, FeB₂ is first employed as a model MBene catalyst for the NO₃ RR, showing a maximum NH₃ -Faradaic efficiency of 96.8 % with a corresponding NH₃ yield of 25.5 mg h^-1 cm^-2 at -0.6 V vs. RHE. Mechanistic studies reveal that the exceptional NO₃ RR activity of FeB₂ arises from the tandem catalysis mechanism, that is, B sites activate NO₃ ^- to form intermediates, while Fe sites dissociate H₂ O and increase *H supply on B sites to promote the intermediate hydrogenation and enhance the NO₃ ^- -to-NH₃ conversion.