Mechanism of N-2 Reduction to NH3 by Aqueous Solvated Electrons

TitleMechanism of N-2 Reduction to NH3 by Aqueous Solvated Electrons
Publication TypeJournal Article
Year of Publication2014
AuthorsChristianson, JR, Zhu, D, Hamers, RJ, Schmidt, JR
JournalJournal of Physical Chemistry B
Volume118
Pagination195-203
Date PublishedJan
Type of ArticleArticle
ISBN Number1520-6106
KeywordsAMMONIA-SYNTHESIS, ATMOSPHERIC-PRESSURE, CARBON-DIOXIDE, Chemistry, Physical, HYDRATED ELECTRON, HYDROGEN-IODINE REACTION, NITROGEN-FIXATION, PHOTOCATALYTIC, RATE CONSTANTS, REDUCTION, ROOM-TEMPERATURE, WATER
Abstract

Recently a novel approach to the photocatalytic reduction of molecular nitrogen under ambient conditions was reported in which hydrated electrons generated from ultraviolet illumination of diamond served as the reducing agent [Zhu, D.; Zhang, L.; Ruther, R. E.; Hamers, R J. Photo-Illuminated Diamond as a Solid-State Source of Solvated Electrons in Water for Nitrogen Reduction. Nat. Mater. 2013, 12, 836-841]. This surprising reduction of N-2 by aqueous solvated electrons is absent from the vast existing radiolysis literature and thus has little mechanistic precedent. In this work, a combination of experimental and computational approaches is used to elucidate the detailed molecular-level mechanistic pathway from nitrogen to ammonia. A variety of approaches, including electronic structure calculations, molecular dynamics simulations, kinetic modeling, and pH-dependent experimental measures of NH3 and competing H-2 production, implicate a hydrogen atom addition mechanism at early reduction steps and sequential protonation/direct reduction by a solvated electron at later steps, thus involving both direct and indirect reactions with solvated electrons. This work provides a framework for understanding the possible application of solvated electrons as energetic reducing agents for chemically inert species under mild conditions.

DOI10.1021/jp406535p