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Photocatalytic oxidation of aqueous ammonia over platinized microwave-assisted titanate nanotubes

Ou, Hsin-Hung and Hoffmann, Michael R. and Liao, Ching-Hui and Hong, Jian-Hao and Lo, Shang-Lien (2010) Photocatalytic oxidation of aqueous ammonia over platinized microwave-assisted titanate nanotubes. Applied Catalysis B, 99 (1-2). pp. 74-80. ISSN 0926-3373. https://resolver.caltech.edu/CaltechAUTHORS:20101004-113244257

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Abstract

Batch experiments were conducted to study the photocatalytic oxidation of aqueous ammonia (NH_3/NH_4^+) over platinized titanate nanotubes (platinized TNTs). The reaction kinetics of NH_3/NH_4^+ oxidation is considerably enhanced by the platinization of TNTs. The observed rate constant (k_(obs)) for NH_3/NH_4^+ oxidation over platinized TNTs was 1.69 × 10^(−2) min^(−1), while the unamended TNTs gave a kobs = 1.23 × 10^(−3) min^(−1). The selectivity of nitrogen gas (N_2) from degraded NH_3/NH_4^+ increased with platinum loading to 87.8% after 1 h photocatalysis. In contrast, NH_3/NH_4^+ to nitrate (NO_3^−) conversion was low due to a large NH_3/NH_4^+ to nitrite (NO)_2^−) energy barrier. High-resolution transmission electron microscopy shows that platinum deposits are formed primarily on the internal surface of the hollow structure of TNTs instead of being deposited on the external surface of TNTs. Based on the analysis of X-ray photoelectron spectroscopy, a mechanism is proposed in which N_2 is produced from the NH_3/NH_4^+ adsorbed on platinum deposits while NO_2^−/NO_3^− is formed from the NH_3/NH_4^+ adsorbed on titanate sites.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.apcatb.2010.06.002 DOIArticle
ORCID:
AuthorORCID
Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 2010 Elsevier. Received 16 February 2010; revised 14 May 2010; accepted 2 June 2010. Available online 12 June 2010. The authors gratefully acknowledge the funding from the National Science Council of Taiwan (NSC 95-2221-E-002-143-MY3).
Funders:
Funding AgencyGrant Number
National Science Council (Taipei)NSC 95-2221-E-002-143-MY3
Subject Keywords:Photocatalysis; Aqueous ammonia; Platinized titanate nanotubes
Issue or Number:1-2
Record Number:CaltechAUTHORS:20101004-113244257
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20101004-113244257
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20281
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:05 Oct 2010 17:31
Last Modified:03 Mar 2020 13:01

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