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submitted on 18.12.2019, 14:43 and posted on 20.12.2019, 13:22by Sayed M. El-Refaei, Patrícia Russo, Patrick Amsalem, Norbert Koch, Nicola Pinna
Coordination polymers (CPs)
and metal-organic frameworks (MOFs) have emerged as versatile precursors for
transition-metal phosphides catalysts. However, the controlled synthesis of
MOF-derived bimetallic phosphides remains a challenge, as mixtures of various
phosphide phases are often formed. Here, it is shown that controlling the
formation of pure CoMoP and CoMoP2 requires a careful choice of the
ligands used to construct the MOF precursors, based on the chemical properties
of the metals. In particular, the nature and number of the coordination
moieties of the ligand play a key role. CoMoP and CoMoP2 particles
coated with N-doped carbon were derived from phosphonate-based MOFs and
compared as hydrogen evolution reaction (HER) electrocatalysts in acidic medium.
CoMoP2 is more active and shows a turnover frequency (TOF) of 0.9 s-1
compared to 0.4 s-1 for CoMoP. The higher intrinsic activity of the
CoMoP2 catalytic sites correlates with the differences in the
electronic structure of the materials, with a larger charge transfer from the
molybdenum to the phosphorous found for CoMoP2.