Adsorbing and Activating N2 on Heterogeneous Au-Fe3O4 Nanoparticles for N2 Fixation

Electrochemical nitrogen reduction reaction (NRR) is a promising approach to convert earth-adundant N-2 into highly value-added NH3. Herein, it is demonstrated that the heterogeneous Au-Fe3O4 nanoparticles (NPs) can be adopted as highly efficient catalysts for NRR. Due to the synergistic effect of the strong N-2 fixation ability of Fe3O4 and the charge transfer capability of Au, the Au-Fe3O4 NPs show excellent performance with a high yield (NH3: 21.42 mu g mg(cat)(-1) h(-1)) and a favorable faradaic efficiency (NH3: 10.54%) at -0.2 V (vs reversible hydrogen electrode), both of which are much better than those of the Au NPs, Fe3O4 NPs, as well as core@shell Au@Fe3O4 NPs. It also exhibits good stability with largely maintained performance after six cycles. The N-2 temperature-programmed desorption, surface valance band spectra, and X-ray photoelectron spectroscopy collectively confirm that Au-Fe3O4 NPs have a strong adsorption capacity for the reaction species and suitable surface structure for electronic transfer. The theoretical calculations reveal that Fe provides the active site to fix N-2 into *N2H while introducing Au optimizes the adsorption of NRR intermediates, making the NRR pathway on Au-Fe3O4 along an energetic-favorable process and enhancing the NRR.