Electrolysis of liquid ammonia for hydrogen generation

Abstract

One route to efficient storage, transportation and utilization of renewable hydrogen is through its conversion into ammonia (NH 3 ). In order to examine the feasibility of an NH 3 fuel cycle, the electrolysis of NH 3 -both as a liquid and dissolved in N,Ndimethylformamide -was investigated using platinum electrodes. The current scaled with electrolyte concentration, but was nominally independent of composition, suggesting solution resistance limitations. NH 3 was found to be the chemical species oxidized at the anode which produced N 2 , but also resulted in a poisoned electrode surface which introduced an additional overpotential of ~0.5 V. Surprisingly, NH 4 + was the species reduced at the cathode via a one-electron transfer process to form NH 4 0 , prior to H 2 generation, which resulted in an additional cathodic overpotential. In addition to establishing the two half reactions of liquid ammonia electrolysis, the formal potentials of the reactions and the kinetic overpotentials were quantified.

Mechanistic insights into copper-catalyzed aerobic oxidative coupling of N–N bonds

“…In this case, a 50% yield of triazole 2 was observed (eqn (2)). These product yields are rationalized according to the balanced equations shown in eqn (1) and (2), which feature Cu II as a one electron oxidant and require a Brønsted base to react with both equivalents of proton in the 2H + /2e À oxidative N-N coupling reaction. In the absence of added benzamidine as a base, the imidoylamidine serves as the base.…”

Homogeneous electrocatalytic oxidation of ammonia to N 2 under mild conditions

“…Electrochemical generation of N 2 and H 2 from NH 3 is possible at ambient and lower temperatures, avoiding the need for heating heterogeneous catalysts for thermal ammonia cracking. For example, low-temperature oxidations of NH 3 (l) to N 2 (g) at Pt and Fe anodes have overpotentials (η) of 1.1 V at current densities of 10 mA/cm 2 (17,18). For efficient electrochemical production of H 2 from NH 3 , the overpotential for NH 3 oxidation to N 2 , protons, and electrons must be lowered.…”

Catalytic Ammonia Oxidation to Dinitrogen by Hydrogen Atom Abstraction

“…[1] NH 3 is ap rominent, large-scale and renewable carbon-free energy source that could augment fossil-based fuels as renewable sources of energy are realized for NH 3 production (i.e., N 2 reduction). [3] Due to its high energy density and flexibility as af uel, NH 3 can be aH 2 storage medium [4][5][6][7] or oxidized directly in NH 3 fuel cells. [3] Due to its high energy density and flexibility as af uel, NH 3 can be aH 2 storage medium [4][5][6][7] or oxidized directly in NH 3 fuel cells.…”