Covalent Functionalization of Nickel Phosphide Nanocrystals with Aryl-Diazonium Salts

21 September 2021, Version 2
This content is a preprint and has not undergone peer review at the time of posting.


Covalent functionalization of Ni2P nanocrystals was demonstrated using aryl-diazonium salts. Spontaneous adsorption of aryl functional groups was observed, with surface coverages ranging from 20-96% depending on the native reactivity of the salt as determined by the aryl substitution pattern. Increased coverage was possible for low reactivity species using a sacrificial reductant. Functionalization was confirmed using thermogravimetric analysis, FTIR and X-ray photoelectron spectroscopy. The structure and energetics of this nanocrystal electrocatalyst system, as a function of ligand coverage, was explored with density functional theory calculations. The Hammett parameter of the surface functional group was found to linearly correlate with the change in Ni and P core-electron binding energies and the nanocrystal’s experimentally and computationally determined work-function. The electrocatalytic activity and stability of the functionalized nanocrystals for hydrogen evolution were also improved when compared to the unfunctionalized material, but a simple trend based on electrostatics was not evident. We used density functional theory to understand this discrepancy and found that H adsorption energies on the covalently functionalized Ni2P also do not follow the electrostatic trend and are predictive descriptors of the experimental results.


transition metal phosphide
covalent functionalization
surface chemistry
diazonium salt

Supplementary materials

Additional experimental details and data
Additional experimental details and data, including Ni2P characterization, NMR spectra, IR, XPS, and electrochemical data, and density functional theory results.


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