Ru Single Atoms Anchored in Metal Borides Enable Hydrogen Spillover for Superior Electrochemical Ammonia Production.

The electrochemical reduction of nitrate represents a promising and sustainable route for valuable ammonia generation. However, a vital challenge in the nitrate reduction reaction is an insufficient supply of active hydrogen (H) and slow kinetics at a low working potential, which result in low production efficiency and high energy consumption. Here, we report the single-atom Ru-decorated nanoporous metal borides as a high-performance electrochemical nitrate reduction electrocatalyst utilizing an atomic-scale hydrogen spillover effect. Notably, the Ru/np-NiB exhibits a high NH Faradaic efficiency of 96.2%, an NH yield of 30.4 mg h mg and an energy efficiency of 39.1% at -0.1 V versus RHE. In situ electrochemical characterizations and theoretical calculations reveal that single-atom Ru anchored in nanoporous NiB not only can efficiently dissociate water into H and simultaneously promote the H spillover for increasing H coverage on the surface but also can optimize surface states of NiB active centers, which synergistically reduces the hydrogenation energy barrier for converting nitrate into valuable ammonia products. A two-electrode electrolyzer integrating nitrate reduction reaction with furfuryl alcohol oxidation reaction achieves current density of 1 A cm at -1.72 V with 100 h stability, improving the energy efficiency and economy of the system.