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Title: Effect of Surface Ligands on CoP for the Hydrogen Evolution Reaction

Abstract

The activity of colloidally synthesized CoP for the hydrogen evolution reaction (HER) was studied to determine the impact of surface ligand on catalysis. The as-synthesized CoP nanocrystals were stripped with trialkyloxonium tetrafluoroborate (Meerwein’s reagent) to create a “blank template” that was then religated with carboxylates (oleate, octanoate, acetate) and amines (oleylamine, octylamine, dioctylamine, trioctylamine butylamine). Carboxylates and amines were chosen due to their prevalence in colloidal syntheses, and the range of ligands was chosen to study the impact of sterics and hydrophobicity of the surface ligands on catalysis. Long chain carboxylates were found to result in a larger increase in overpotential when compared to the equivalent amine (e.g., oleate vs oleylamine), due to higher ligand density and stronger coordination with carboxylates. Increased carbon chain length resulted in increased overpotential with carboxylates; however, the range of 1° amines studied had similar overpotentials. This is due to the lower ligand density and therefore sparse ligand packing for the 1° amines. These results suggest that the mechanism by which surface ligands impede catalysis on CoP for HER is primarily through inhibiting substrate access to surface active sites rather than poisoning the active sites.

Authors:
 [1];  [1]
  1. University of Washington
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1542079
Report Number(s):
PNNL-SA-141722
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
ACS Applied Energy Materials
Additional Journal Information:
Journal Volume: 2; Journal Issue: 3
Country of Publication:
United States
Language:
English
Subject:
cobalt phosphide, hydrogen evolution reaction, ligand effects, colloidal synthesis, Meerwein’s reagent

Citation Formats

Ung, David, and Cossairt, Brandi M. Effect of Surface Ligands on CoP for the Hydrogen Evolution Reaction. United States: N. p., 2019. Web. doi:10.1021/acsaem.9b00240.
Ung, David, & Cossairt, Brandi M. Effect of Surface Ligands on CoP for the Hydrogen Evolution Reaction. United States. doi:10.1021/acsaem.9b00240.
Ung, David, and Cossairt, Brandi M. Mon . "Effect of Surface Ligands on CoP for the Hydrogen Evolution Reaction". United States. doi:10.1021/acsaem.9b00240.
@article{osti_1542079,
title = {Effect of Surface Ligands on CoP for the Hydrogen Evolution Reaction},
author = {Ung, David and Cossairt, Brandi M.},
abstractNote = {The activity of colloidally synthesized CoP for the hydrogen evolution reaction (HER) was studied to determine the impact of surface ligand on catalysis. The as-synthesized CoP nanocrystals were stripped with trialkyloxonium tetrafluoroborate (Meerwein’s reagent) to create a “blank template” that was then religated with carboxylates (oleate, octanoate, acetate) and amines (oleylamine, octylamine, dioctylamine, trioctylamine butylamine). Carboxylates and amines were chosen due to their prevalence in colloidal syntheses, and the range of ligands was chosen to study the impact of sterics and hydrophobicity of the surface ligands on catalysis. Long chain carboxylates were found to result in a larger increase in overpotential when compared to the equivalent amine (e.g., oleate vs oleylamine), due to higher ligand density and stronger coordination with carboxylates. Increased carbon chain length resulted in increased overpotential with carboxylates; however, the range of 1° amines studied had similar overpotentials. This is due to the lower ligand density and therefore sparse ligand packing for the 1° amines. These results suggest that the mechanism by which surface ligands impede catalysis on CoP for HER is primarily through inhibiting substrate access to surface active sites rather than poisoning the active sites.},
doi = {10.1021/acsaem.9b00240},
journal = {ACS Applied Energy Materials},
number = 3,
volume = 2,
place = {United States},
year = {2019},
month = {3}
}