Experimental and Theoretical Identifications of Durable Fe–Nx Configurations Embedded in Graphitic Carbon Nitride for Uranium Photoreduction

Uranium extraction from seawater has attracted increasing attentions for nuclear raw material to support the sustainable development of nuclear power plants. However, it is still a grand challenge to overcome the high salinity background and ultra-low uranyl concentration. Herein, we successfully achieved Fe-N x configurations embedded in graphitic carbon nitride (FeN x /g-C 3 N 4 ) through one-step pyrolysis strategy. Our density function theory (DFT) calculations reveal that the site-isolated FeN x centers are the predominant binding sites for U(VI) species, and visible-light photoexcitation can effectively facilitate the electron escaping from FeN x /g-C 3 N 4 surface relative to pure g-C 3 N 4 , which is consequently favorable for electron transfer in the photoreduction conversion of U(VI) to U(IV). Consistent with the theoretical results, the obtained FeN x /g-C 3 N 4 delivers remarkably higher reduction activity with the conversion efficiency of 99% and rate constant of 0.091 min -1 , almost 9.1 and 12.5 times faster than those of g-C 3 N 4 and TiO 2 catalysts, respectively. It is worthwhile to mention that FeN x /g-C 3 N 4 maintains a high level for the extraction of uranium from seawater, endowing the metal-N configurations embedded g-C 3 N 4 as a kind of promising candidate for the sustainable conversion of radionuclides