Direct Nitrogen Oxidation\nvia Pd Nanoparticle Electrocatalysis

Palladium\nnanoparticles with two different ligands were used as\nelectrocatalysts at low temperature in a hermetic one-pot electrochemical\ncell with either a LiOH or a LiOD electrolyte. During initial low-pressure\nexperiments involving Pd nanoparticle electrocatalysts with epigallocatechin\ngallate (EGCG) ligands, an abrupt, significant pressure drop occurred\nin the cell headspace air from 1.59 to 0.055 bar. This astounding,\nrepeatable, and unexplained result initiated further experimentation.\nSynthetic methods for bifunctional Pd nanoparticle electrocatalysts\nwith EGCG ligands and poly(vinylpyrrolidone) (PVP) ligands are described.\nThese Pd nanoparticles are capable of simultaneously generating ammonium,\nnitrite, and nitrate ions. Ion chromatography was used for quantification\nof nitrogen-containing anions and cations in an alkaline electrolyte.\nThe Pd nanoparticles with PVP ligands and a 5 bar 3:1 H<sub>2</sub>/N<sub>2</sub> gas mixture resulted in a nitrate yield rate of 1.16\nμg h<sup>–1</sup> mg<sub>cat</sub><sup>–1</sup> with current applied for 132 h.\nThe Pd–PVP nanoparticles also achieved the highest ammonium\nand nitrite ion yield rates at 10 bar under similar conditions, while\nthe Pd–EGCG nanoparticles achieved lower yield rates and Faradaic\nefficiency (FE) values. This study demonstrates that direct generation\nof nitrite and nitrate salts avoids the need to further process ammonia\nto produce ammonium nitrate.