Interlayer Coordination of Pd-Pd Units in Exfoliated Black Phosphorus

The chemical functionalization of 2D exfoliated black phosphorus (2D BP) continues to attract great interest, although a satisfactory structural characterization of the functionalized material has seldom been achieved. Herein, we provide the first complete structural characterization of 2D BP functionalized with rare discrete Pd-2 units, obtained through a mild decomposition of the organometallic dimeric precursor [Pd(eta(3)-C3H5)Cl](2). A multitechnique approach, including HAADF-STEM, solid-state NMR, XPS, and XAS, was used to study in detail the morphology of the palladated nanosheets (Pd-2/BP) and to unravel the coordination of Pd-2 units to phosphorus atoms of 2D BP. In particular, XAS, backed up by DFT modeling, revealed the existence of unprecedented interlayer Pd-Pd units, sandwiched between stacked BP layers. The preliminary application of Pd-2/BP as a catalyst for the hydrogen evolution reaction (HER) in acidic medium highlighted an activity increase due to the presence of Pd-2 units.

Automated summary

This study provides the first complete structural characterization of 2D BP functionalized with rare discrete Pd-2 units, revealing the existence of interlayer Pd-Pd units and an increase in catalytic activity for the hydrogen evolution reaction. Multiple techniques were utilized to study the morphology of Pd-2/BP nanosheets and to uncover the coordination of Pd-2 units to phosphorus atoms in 2D BP. The presence of Pd-2 units was found to enhance the activity of Pd-2/BP as a catalyst for HER in acidic medium.