Homogeneous electrocatalytic oxidation of ammonia to N ₂ under mild conditions

Abstract

We report that ruthenium polypyridyl complexes can catalyze ammonia oxidation to dinitrogen at room temperature and ambient pressure. During bulk electrolysis experiments, gas chromatography and mass spectrometry analysis of the headspace in the electrochemical cell showed that dinitrogen and dihydrogen are generated from ammonia with high faradaic efficiencies. A proposed mechanism where a hydrazine complex is the initial N–N bonded intermediate is supported by chemical and electrochemical experiments. This is a well-defined system for homogeneous electrocatalytic ammonia oxidation. It establishes a platform for answering mechanistic questions relevant to using ammonia to store and distribute renewable energy.

Catalytic Ammonia Oxidation to Dinitrogen by Hydrogen Atom Abstraction

“…Asynthetic cycle for NH 3 oxidation to N 2 has been achieved employing aM n(salen) complex. [24] Ther emoval of six electrons and six protons from two NH 3 molecules,and the key step of forming the N Nb ond is ac hallenging endeavor;consequently,molecular catalysts for the oxidation of NH 3 to N 2 are rare and systems that operate thermally remain elusive. [24] Ther emoval of six electrons and six protons from two NH 3 molecules,and the key step of forming the N Nb ond is ac hallenging endeavor;consequently,molecular catalysts for the oxidation of NH 3 to N 2 are rare and systems that operate thermally remain elusive.…”

Homogeneous catalysis for the nitrogen fuel cycle

“…A study in PNAS by Habibzadeh et al (3) reports that ruthenium polypyridyl complexes can be used as electrocatalysts for the oxidation of ammonia to dinitrogen and dihydrogen at ambient pressures and temperature. The results from Habibzadeh et al (3) are an important extension of the remarkable highoxidation-state chemistry of these complexes with Ru II and Os II . Known examples in this chemistry include catalysts for water oxidation, catalytic organic oxidations, and a remarkable series of inorganic reactions such as the oxidation of NH 3 to NO 3 − , all in polypyridyl coordination environments.…”

Host-Guest Interactions on Electrode Surfaces for Immobilization of Molecular Catalysts

“…15,19,29,30 As guests, we chose to investigate ruthenium-based electrocatalyst 2, inspired by the class of molecular catalysts that has very 5 recently been shown to be active for ammonia oxidation in organic electrolytes (ammonia being a promising candidate as storage medium for hydrogen). [31][32][33][34] We also investigated structurally similar ruthenium-based electrocatalyst 3, a derivate of which we have reported to be active for water oxidation. 35 As a control, fluorescent platinum complex 4 was synthesized, which served as a non-electroactive guest.…”