Title

Mild and Selective Hydrogenation of Nitrate to Ammonia in the Absence of Noble Metals

Publication Date

2-21-2020

Department

Ames Laboratory; Chemistry; Physics and Astronomy

Campus Units

Ames Laboratory, Chemistry, Physics and Astronomy

OSTI ID+

1609161

Report Number

IS-J 10163

DOI

10.1021/acscatal.9b05338

Journal Title

ACS Catalysis

Volume Number

10

Issue Number

6

First Page

3618

Last Page

3628

Abstract

Motivated by increased awareness about nitrate contamination of surface waters and its deleterious effects in human and animal health, we sought an alternative, non-noble metal catalyst for the chemical degradation of nitrate. First row transition metal phosphides recently emerged as excellent alternatives for hydrogen evolution and hydrotreating reactions. We demonstrate that a key member of this family, Ni2P, readily hydrogenates nitrate (NO3–) to ammonia (NH3) near ambient conditions with very high selectivity (96%). One of the few non-precious metal-based catalysts for this transformation, and among ca. 1% of catalysts with NH3 selectivity, Ni2P can be recycled multiple times with limited loss of activity. Both nitrite (NO2–) and nitric oxide (NO) intermediates are also hydrogenated. Density functional theory (DFT) indicates that—in the absence of a catalyst—nitrite hydrogenation is the reaction bottleneck. A variety of adsorbates (H, O, N, NO) induce surface reconstruction with top-layer Ni-rich surface stoichiometry. Critically, H saturation coverage on Ni2P(001) is only ca. 3 nm–2, significantly less than that on Pd(111) and Ni(111) of ca. 15–18 nm–2, which may play a key role in allowing coadsorption of NOx–. The ability of Earth-abundant, binary metal phosphides such as Ni2P to catalyze nitrate hydrogenation could transform and help us to better understand the basic science behind catalytic hydrogenation and, in turn, advance the next generation of oxyanion removal technologies.

DOE Contract Number(s)

1905066; AC02-07CH11358

Language

en

Publisher

Iowa State University Digital Repository, Ames IA (United States)

IS-J 10163 SI.pdf (563 kB)
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