In Situ Attenuated Total Reflection Infrared Spectroscopy on Electrochemical Ammonia Oxidation over Pt Electrode in Alkaline Aqueous Solutions

Abstract

The electrochemical oxidation of ammonia over Pt electrode in alkaline aqueous solutions was studied by in situ attenuated total reflection infrared (ATR-IR) spectroscopy. In 0.1 M NH3-1 M KOH, the band ascribable to the HNH bending mode of adsorbed NH3 was confirmed at 1662-1674 cm(-1) in the potential range of 0.1-1.1 V. The intensity of this band decreased continuously with a rise in potential, indicating the oxidative consumption of adsorbed ammonia. In response to this behavior, the band at 1269 cm(-1) appeared alternatively above 0.2 V, and its intensity reached the local maximal value at ca. 0.4 V. Note that this potential of ca. 0.4 V agreed well with the onset potential of ammonia oxidation, ca. 0.45 V, in the linear sweep voltammogram. This 1269 cm(-1) band was assigned to the NH2 wagging mode of N2H4, which was one of the active intermediates, N2H(x+y,ad) (x = 1 or 2, y = 1 or 2), according to the mechanism proposed by Gerischer and Mauere. To the best of our knowledge, this is the first report for the detection of N2H4 as a reaction intermediate over Pt electrode. Furthermore, the formation of bridged NO was also observed above the onset potential of ammonia oxidation, ca. 0.5 V. Such adsorbed NO species probably inhibit the electrochemical reaction due to the occupation of reaction sites at higher potential.

Electrochemical oxidation of 2-propanol over platinum and palladium electrodes in alkaline media studied by in situ attenuated total reflection infrared spectroscopy

“…30,33 The Si prism was polished sequentially by 1.0 mm and 0.125 mm diamond suspension and 0.05 mm alumina suspension, and then the smooth surface was etched by 40 wt% NH 4 F (98.5%, Wako Pure Chemical). 30,33 The Si prism was polished sequentially by 1.0 mm and 0.125 mm diamond suspension and 0.05 mm alumina suspension, and then the smooth surface was etched by 40 wt% NH 4 F (98.5%, Wako Pure Chemical).…”

“…33 The Pt or the Pd film electrode on the Si prism was applied as a working electrode. 33 The Pt or the Pd film electrode on the Si prism was applied as a working electrode.…”

“…1 shows the LSVs of the Pt film electrode in the absence and presence of 1 M 2-propanol in 0.25 M KOH at a scanning rate of 20 mV s À1 . 30,33,35 When the potential was lower than the onset potential of 2-propanol (o0.25 V), there were no definite peaks in the spectra. The onset potential for 2-propanol oxidation was 0.25 V, which was comparable to the results obtained under acidic conditions as reported before.…”

Enhancement of ammonia oxidation activity over Y2O3-modified platinum surface: Promotion of NH2,ad dimerization process

“…This reaction mechanism has been supported by the coulometric experiment 16 , differential electrochemical mass spectroscopy (DEMS) 17 18 , surface enhanced Raman spectroscopy (SERS) 19 20 , and in situ attenuated total reflection infrared (ATR-IR) spectroscopy. 21 According to this mechanism, NH2,ad and NHad species are produced on the Pt electrode by the sequential ammonia dehydrogenation with the aid of OHad species, and subsequently combined each other through the catalytic reaction to form N2Hx+y,ad (x = 1 or 2, y = 1 or 2 ). Finally, the further dehydrogenation of N2Hx+y,ad leads to the formation of N2.…”

Nitrogen-doped Fe3C@C particles as an efficient heterogeneous photo-assisted Fenton catalyst

“…Industrially realized methods including absorption, occulation and chemical oxidation have been applied to address this problem. [3][4][5] Among chemical oxidation technologies that lead to complete destruction of organic pollutant molecules, the Fenton reaction, where ferrous ions and hydrogen peroxide react to generate highly reactive hydroxyl radicals in aqueous solution, has drawn intensive attention owing to its reliable performance. In conventional homogeneous Fenton systems composed of dissolved Fe 2+ /Fe 3+ species and hydrogen peroxide, hydroxyl radicals generated within the system can rapidly oxidize organic pollutants.…”