Sub-nm RuOX Clusters on Pd Metallene for Synergistically Enhanced Nitrate Electroreduction to Ammonia

The electrochemical nitrate reduction to ammonia reaction (NO3RR) has emerged as an appealing route for achieving both wastewater treatment and ammonia production. Herein, sub-nm RuOx clusters anchored on a Pd metallene (RuOx/Pd) are reported as a highly effective NO3RR catalyst, delivering a maximum NH3-Faradaic efficiency of 98.6% with a corresponding NH3 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 RuOx and Pd to enhance the NO3RR energetics through a mechanism of hydrogen spillover and hydrogen-bond interactions. In detail, RuOx activates NO3- to form intermediates, while Pd dissociates H2O to generate *H, which spontaneously migrates to the RuOx/Pd interface via a hydrogen spillover process. Further hydrogen-bond interactions between spillovered *H and intermediates makes spillovered *H desorb from the RuOx/Pd interface and participate in the intermediate hydrogenation, contributing to the enhanced activity of RuOx/Pd for NO3--to-NH3 conversion.