Thermolysis of Noble Metal Nanoparticles into Electron-Rich Phosphorus-Coordinated Noble Metal Single Atoms at Low Temperature

Noble metal single atoms coordinated with highly electronegative atoms, especially N and O, often suffer from an electron-deficient state or poor stability, greatly limiting their wide application in the field of catalysis. Herein we demonstrate a new PH₃-promoted strategy for the effective transformation of noble metal nanoparticles (MNPs, M=Ru, Rh, Pd) at a low temperature (400 °C) into a class of thermally stabilized phosphorus-coordinated metal single atoms (MPSAs) on g-C₃N₄ nanosheets via the strong Lewis acid–base interaction between PH₃ and the noble metal. Experimental work along with theoretical simulations confirm that the obtained Pd single atoms supported on g-C₃N₄ nanosheets exist in the form of PdP₂ with a novel electron-rich feature, conceptionally different from the well-known single atoms with an electron-deficient state. As a result of this new electronic property, PdP₂-loaded g-C₃N₄ nanosheets exhibit 4 times higher photocatalytic H₂ production activity than the state-of-art N-coordinated PdSAs supported on g-C₃N₄ nanosheets. This enhanced photocatalytic activity of phosphorus-coordinated metal single atoms with an electron-rich state was quite general, and also observed for other active noble metal single atom catalysts, such as Ru and Rh.