Highly efficient electrocatalytic nitrogen fixation enabled by the bridging effect of Ru in plasmonic nanoparticles

Plasmon-generated hot electrons show great potential for driving chemical reactions. The utilization efficiency of hot electrons is highly dependent on the interaction of the electronic states at the interfaces between plasmonic nanoparticles and other materials/molecules. Strong interaction can produce new hybridized electron states, which permit direct hot-electron transfer, a more efficient transfer mechanism. However, Au usually has very weak interaction with most molecules because of its inertness, which makes direct hot-electron transfer impossible. Herein, the improvement of the hot-electron transfer efficiency from Au to N₂ is demonstrated by introducing a Ru bridging layer. Both the N₂ fixation rate and Faradic efficiency (FE) are enhanced by the excitation of plasmons. The enhancement of the N₂ fixation rate is found to arise from plasmon-generated hot electrons. Theoretical calculations show that the strong interaction of the Ru electronic states with the N₂ molecular orbitals produces new hybridized electronic states, and the Ru d electrons also strongly couple with the Au sp electrons. Such a bridging role of Ru makes direct hot-electron transfer from Au to N₂ possible, improving the FE of nitrogen fixation. Our findings demonstrate a new approach to increasing the utilization efficiency of plasmonic hot electrons for chemical reactions and will be helpful to the design of plasmonic catalysts in the future.