Sub-nm RuO x Clusters on Pd Metallene for Synergistically Enhanced Nitrate Electroreduction to Ammonia.

The electrochemical nitrate reduction to ammonia reaction (NO 3 RR) has emerged as an appealing route for achieving both wastewater treatment and ammonia production. Herein, sub-nm RuO x clusters anchored on a Pd metallene (RuO x /Pd) are reported as a highly effective NO 3 RR catalyst, delivering a maximum NH 3 -Faradaic efficiency of 98.6% with a corresponding NH 3 yield rate of 23.5 mg h -1 cm -2 and partial a current density of 296.3 mA cm -2 at -0.5 V vs RHE. Operando spectroscopic characterizations combined with theoretical computations unveil the synergy of RuO x and Pd to enhance the NO 3 RR energetics through a mechanism of hydrogen spillover and hydrogen-bond interactions. In detail, RuO x activates NO 3 - to form intermediates, while Pd dissociates H 2 O to generate *H, which spontaneously migrates to the RuO x /Pd interface via a hydrogen spillover process. Further hydrogen-bond interactions between spillovered *H and intermediates makes spillovered *H desorb from the RuO x /Pd interface and participate in the intermediate hydrogenation, contributing to the enhanced activity of RuO x /Pd for NO 3 - -to-NH 3 conversion.