Direct Nitrogen Oxidation via Pd-nanoparticle Electrocatalysis

18 October 2024, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Palladium nanoparticles with two different ligands were used as electrocatalysts at low temperature in a hermetic, one-pot electrochemical cell with either a LiOH or LiOD electrolyte. During initial, low-pressure experiments involving palladium (Pd) nanoparticle electrocatalysts with Epigallocatechin Gallate (EGCG) ligands an abrupt, significant pressure drop occurred in the cell headspace air from 1.59 to 0.055 bar. This astounding, repeatable, and unexplained result initiated further experimentation. Synthetic methods for Pd nanoparticle electrocatalysts with EGCG ligands and with polyvinylpyrrolidone (PVP) ligands are described. These Pd nanoparticles are capable of simultaneously generating ammonium, nitrite, and nitrate ions. Ion chromatography was used for quantification of nitrogen-containing anions and cations in the alkaline electrolyte. The Pd nanoparticles with PVP ligands and a 5 bar 3:1 H2/N2 gas mixture resulted in a nitrate yield rate of 1.16 µg h−1 mg−1 with current applied for 132 hr. The Pd nanoparticles with PVP ligands also achieved the highest ammonium and nitrite ion yield rates at 10 bar under similar conditions while the Pd-EGCG nanoparticles achieved lower yield rates Faradaic efficiencies (FE) values. This study demonstrates that direct generation of nitrite and nitrate salts avoids the need to further process ammonia into ammonium nitrate.

Keywords

Electrochemical Nitrogen Oxidation
Nitrogen Fixation
Electrochemical Nitrate Production
Electrochemical Nitrite Production
Palladium Nanoparticles
EGCG Ligands
PVP Ligands

Supplementary materials

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Title
Supporting Information for Direct Nitrogen Oxidation via Pd-nanoparticle Electrocatalysis
Description
The supporting information includes descriptions of the analytical methods for the determination of the ammonium cations, the nitrite, and the nitrate anions. It also describes the three cell types used, the electrical configuration including the DC power supply, and the sensors used. It includes the results of the control experiments with different headspace gases, of the initial experiments containing air, and of experiments conducted with a H2 and N2 (3:1)gas mixture in the headspace.
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