Ammonia　(NH3)　synthesis　with　hydrogen　(H2)　produced　from　renewable　energy　is　a　promising　route　to　reduce　carbon　footprints　and　the　dependence　on　fossil　fuels.　However,　the　development　of　highly　efficient　and　stable　catalyst　for　NH3　synthesis　under　mild　conditions　is　a　challenge.　Herein,　a　series　of　boron　nitride　(BN)-supported　Ru　catalysts　were　synthesized,　and　the　NH3　synthesis　rate　was　enhanced　significantly　after　the　introduce　of　Ce.　The　developed　RuCe2.4/BN　catalyst　with　a　Ce/Ru　molar　ratio　of　2.4　exhibited　the　optimal　NH3　synthesis　rate　of　14.6　mmolNH3　gcat−1　h−1　at　400　°C　and　1.0　MPa,　which　was　∼21-fold　that　of　the　catalyst　prepared　without　Ce.　In　situ　diffuse　reflectance　infrared　Fourier　transform　spectroscopy　of　CO　adsorption　and　X-ray　photoemission　spectroscopy　coupled　with　electron　energy　loss　spectroscopy　revealed　that　the　d-d　electronic　interaction　between　Ru　and　CeO2　can　be　differentially　adjusted　by　a　change　in　the　Ce/Ru　molar　ratio.　An　appropriate　amount　of　Ce　could　enhance　the　electronic　interaction　between　the　CeOy　overlayer　and　Ru　entities.　Also,　the　CeOy　overlayer　acted　as　an　“electron　shuttle”　and　enhanced　the　charge　transfer　from　Ce　to　the　surface　of　Ru　atoms.　Finally,　electron　donation　occurred　from　the　surface　abundancy　of　Ru　atoms　to　N2　molecule　through　a　d-π*　interaction.　Moreover,　the　introduction　of　excessive　Ce　could　block　Ru　active　sites,　weaken　the　electron　transfer　and,　therefore,　decrease　the　NH3　synthesis　rate.　©　2023　The　Royal　Society　of　Chemistry.