Rh-Based Catalysis Chemistry of Aqueous-Phase Nitrogen Treatment Reactions
type: CreativeWork
description: Over the past century, the increase in human population has driven a need for the increased fixation of atmospheric nitrogen to produce nitrogen-based fertilizers and munitions. These anthropogenic processes have led to significant pollution of freshwater by inorganic nitrogen species (e.g. NO3-, NO2-, NH4+). Nitrate (NO3-) and nitrite (NO2-) consumption is toxic to humans, and ammonia/ammonium (NH3/NH4+) is toxic to aquatic life. Both the oxidized and reduced species contribute towards eutrophication and soil acidification. Catalytic denitrification has emerged as a promising technology for the remediation of nitrogen-contaminated waters. The primary goal of this work is to investigate rhodium (Rh)-based catalysts for the remediation of inorganic nitrogen contaminants in water. This study addresses the effects of pH and salinity on the catalytic mechanism of nitrate/nitrite hydrogenation. A new support material for Rh was developed and a bifunctional reaction mechanism was found for ammonia oxidation. This work provides new insights into nitrogen conversion mechanisms in water over Rh, and insights into the design of active and selective catalysts for a desired treatment application. The NO2- reduction properties of alumina-supported Rh were investigated using Pd as a benchmark, where the bulk solution pH was varied to probe the effect of reaction conditions on the catalytic chemistry. Pd expectedly showed high reduction activity and high N2 selectivity at low pH, and near inactivity at high pH. Rh, while inactive at low pH, showed moderate activity and high NH4+ selectivity at high pH. Hydrazine (N2H4) was also detected as a reaction intermediate when NH4+ was formed. Density functional theory (DFT) simulations of the reactions performed by collaborators revealed new insights into the reaction mechanism at different pH, which were corroborated by in aqua surface-enhanced Raman spectroscopy (SERS). These results update the common view that only Pd-based catalysts a…
abstract: Over the past century, the increase in human population has driven a need for the increased fixation of atmospheric nitrogen to produce nitrogen-based fertilizers and munitions. These anthropogenic processes have led to significant pollution of freshwater by inorganic nitrogen species (e.g. NO3-, NO2-, NH4+). Nitrate (NO3-) and nitrite (NO2-) consumption is toxic to humans, and ammonia/ammonium (NH3/NH4+) is toxic to aquatic life. Both the oxidized and reduced species contribute towards eutrophication and soil acidification. Catalytic denitrification has emerged as a promising technology for the remediation of nitrogen-contaminated waters. The primary goal of this work is to investigate rhodium (Rh)-based catalysts for the remediation of inorganic nitrogen contaminants in water. This study addresses the effects of pH and salinity on the catalytic mechanism of nitrate/nitrite hydrogenation. A new support material for Rh was developed and a bifunctional reaction mechanism was found for ammonia oxidation. This work provides new insights into nitrogen conversion mechanisms in water over Rh, and insights into the design of active and selective catalysts for a desired treatment application. The NO2- reduction properties of alumina-supported Rh were investigated using Pd as a benchmark, where the bulk solution pH was varied to probe the effect of reaction conditions on the catalytic chemistry. Pd expectedly showed high reduction activity and high N2 selectivity at low pH, and near inactivity at high pH. Rh, while inactive at low pH, showed moderate activity and high NH4+ selectivity at high pH. Hydrazine (N2H4) was also detected as a reaction intermediate when NH4+ was formed. Density functional theory (DFT) simulations of the reactions performed by collaborators revealed new insights into the reaction mechanism at different pH, which were corroborated by in aqua surface-enhanced Raman spectroscopy (SERS). These results update the common view that only Pd-based catalysts a…
author: Clark, Chelsea A
language: eng
keywords: rhodium, catalytic denitrification, catalyst, surface-enhanced raman spectroscopy, nitrate, nitrite, ammonium, ammonia
date published: 2020-12-01
date modified: 2026-07-24T04:10:37Z
provider: Rice University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Rice University

PropertyValue
property ID: Handle
value: https://hdl.handle.net/1911/109598