Covalent Functionalization of Nickel Phosphide Nanocrystals with Aryl-Diazonium Salts

19 July 2021, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

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 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.

Keywords

transition metal phosphide
nanocrystal
covalent functionalization
surface chemistry
diazonium salt

Supplementary materials

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