Evaluating the Thermodynamics of Electrocatalytic N 2 Reduction in Acetonitrile
The synthesis of ammonia by proton-coupled electroreduction of dinitrogen (N2) represents a sustainable alternative to currently practiced hydrogenation methods. Developments in this area require knowledge of the standard reduction potentials that describe the thermodynamics of N2 reduction. The first collection of N2 reduction standard potentials in organic solvent are reported here. The potentials for reduction of N2 to ammonia (NH3), hydrazine (N2H4), and diazene (N2H2) in acetonitrile (MeCN) solution are derived using thermochemical cycles. Ammonia is the thermodynamically favored product, with a 0.43 V difference between NH3 and N2H4 and a 1.26 V difference between NH3 and N2H2. The thermodynamics for reduction of N2 to the protonated products ammonium (NH4+) and hydrazinium (N2H5+) under strongly acidic conditions are also presented. Comparison with previously determined values for the H+/H2 potential in MeCN reveals a 63 mV thermodynamic preference for N2 reduction to NH3 over H2 production. Combined with knowledge of the kinetics of electrode-catalyzed H2 evolution, a wide working region is identified to guide future electrocatalytic studies.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Energy Frontier Research Centers (EFRC) (United States). Center for Molecular Electrocatalysis (CME)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1340824
- Report Number(s):
- PNNL-SA-119958; KC0307010
- Journal Information:
- ACS Energy Letters, Vol. 1, Issue 4; ISSN 2380-8195
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
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