Fe Single-Atom Catalyst for Visible-Light-Driven Photofixation of Nitrogen Sensitized by Triphenylphosphine and Sodium Iodide
Tingting Hou, Hailong Peng, Xin Yue, Sanmei Wang, Wenkun Zhu, Lanlan Chen, Yuan Yao, Wenhua Zhang, Shuquan Liang, Liangbing Wang
Abstract
Photosensitizers with charge-separated excited states are commonly introduced into photocatalytic systems to accomplish photon-to-electron transformation. Unfortunately, the photosensitizers in current use are mostly precious metal complexes and synthetically elaborate organic dyes. Herein, we successfully applied a low-cost triphenylphosphine (PPh3)/sodium iodide (NaI)-based photosensitizer to heterogeneous catalysis using Fe single-atom catalysts (Fe1/C) toward N2 photofixation. PPh3 molecules mainly adsorbed on the active carbon to form Fe1/C–PPh3/NaI. During N2 photofixation, Fe1/C–PPh3/NaI exhibited an NH3 production rate of 98 μmol/(gcat.·h) without any sacrificial agents, even 1.5 times as high as that for Fe1/C using tris(2,2′-bipyridyl)dichlororuthenium(II) ([Ru(bpy)3]Cl2) as the photosensitizer. Further mechanistic studies revealed that Fe1/C–PPh3/NaI effectively harvested photons by delivering hot electrons from adsorbed PPh3/NaI to Fe single atoms under light irradiation, together with the generation of PPh3-I• radicals. The hot electrons reduced N2 to NH3 over Fe single atoms, while PPh3-I• radicals were regarded to oxidize H2O to O2.