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. Noble metal nanoparticles (MNPs, M=Ru, Rh, Pd) on g‐C3N4 nanosheets can be transformed by reaction with PH3 into supported thermally stabilized phosphorus‐coordinated metal single atoms (MPSAs, M=Ru, Rh, Pd) at 400 °C. For Pd, the single‐atom catalytic sites exist as PdP2 with exceptional activity for the hydrogen evolution reaction.