Electrocatalytic Reduction of Nitrate over Palladium Nanoparticle Catalysts

Abstract

The electrocatalytic reduction of 0.5 M nitrate in 1 M HClO 4 over carbon-supported palladium nanoparticles ͑mean size 10.5 nm͒ was studied with differential electrochemical mass spectrometry ͑DEMS͒ as a function of reaction temperature between 0 and 55°C. The palladium nanoparticles are active for the electrocatalytic reduction of nitrate as evidenced by the detection of N 2 O and NO in DEMS. NO is produced during the anodic scan between 0.8 and 1.0 V vs reversible hydrogen electrode ͑RHE͒ and also during the cathodic scan between 0.3 and 0.0 V vs RHE. In contrast, N 2 O is only produced during the cathodic scan between 0.4 and 0.0 V vs RHE. While the reduction of NO 3 − to NO and N 2 O during the cathodic scan occurs only at significant overpotentials, the required overpotential decreases with increasing temperature. The potential dependencies of the apparent activation energies for the cathodic NO and N 2 O production indicate that at potentials above 0.1 and 0.075 V vs RHE, the respective kinetics of NO and N 2 O evolution are primarily determined by the potential. At potentials below 0.1 and 0.075 V vs RHE, respectively, the apparent activation energies for the evolution of NO and N 2 O are largely potential independent.

Photocatalytic disproportionation of nitrite to dinitrogen and nitrate in an aqueous suspension of metal-loaded titanium(iv) oxide nanoparticles

“…Since NO 2 À reacts with secondary amines yielding nitrosoamines, which are carcinogens, ingestion of a large excess of NO 2 À should be avoided. The nitrite ion is often formed as a relatively stable intermediate in the processes of nitrate ion (NO 3 À ) reduction by catalysis, 1-9 electrocatalysis [10][11][12][13][14][15][16][17] and photocatalysis 9,[18][19][20][21][22][23][24][25][26][27][28][29][30][31] using dihydrogen (H 2 ), electrically supplied electrons and photogenerated electrons. However, reduction of NO 3 À and NO 2 À by the above methods mainly or partially yielded NH 3 or ammonium ion (NH 4…”

Simultaneous removal of nitrite and ammonia as dinitrogen in aqueous suspensions of a titanium(iv) oxide photocatalyst under reagent-free and metal-free conditions at room temperature

“…Since NO 2 À reacts with secondary amines to yield nitrosoamines, which are carcinogens, ingestion of a large amount of NO 2 À should be avoided. Nitrite ion is oen formed as a relatively stable intermediate in the processes of nitrate ion (NO 3 À ) reduction by catalysis, 1-9 electrocatalysis [10][11][12][13][14][15][16][17] and photocatalysis 9,18-33 using dihydrogen (H 2 ), electrically supplied electrons and photogenerated electrons, respectively. However, reduction of NO 3 À and NO 2 À by the above methods has mainly or partially yielded NH 3 or ammonium ion (NH 4 + ), in which nitrogen is over-reduced.…”

Nanoparticles in the Water Cycle

“…Nitrate is converted to N 2 by nZVI particles (Choe et al, 2000) due to an aciddriven surface-mediated process. Carbon-supported palladium nanoparticles as well as titania-coated nano-hematite can be used for the electrocatalytic reduction of NO 3 - (Andrade et al, 2007;Penpolcharoen et al, 2001). Rengaraj and Li (2007) prepared a series of Bi 3+ -doped TiO 2 catalysts with a doping concentration up to 2 wt% and evaluated their catalytic activity in the photochemical reduction of nitrate under UV-light.…”