Photocatalytic Reactions of Azide Ions on Platinized Titanium Dioxide Powders in Solutions

Abstract

Ammonia was formed photocatalytically from an aqueous solution of azide ion by using illuminated Pt/TiO2 semiconductor powder. The reaction products, NH3, N2, and small amounts of N2O and NO3−, were detected. Hydrogen, O2 and N2H4 were not formed in the primary reaction products. From these results, together with photoelectrochemical measurements, a mechanism of the ammonia formation from azide ion and water is presented.

Generation and Detection of Reactive Oxygen Species in Photocatalysis

“…Decrease of furfuryl alcohol, a kind of furan, was used as an indicator to estimate the concentration of 1 O 2 generated in photocatalysis . In some cases, the role of 1 O 2 in photocatalytic reactions was elucidated by the addition of sodium azide (NaN 3 ) which is expected to quench 1 O 2 . − However, azido ion is easily oxidized to N 2 and N 2 O by photocatalysts . Hence, the generation of ROS might be suppressed.…”

“…187−191 However, azido ion is easily oxidized to N 2 and N 2 O by photocatalysts. 192 Hence, the generation of ROS might be suppressed. Though the quenchers, such as azido ion in the case of 1 O 2 , are added aiming to react with the produced ROS, the decrease may not be caused by the reaction with the quencher, but the decrease would actually occur in the generation of ROS on the addition of the quencher.…”

Electrochemical Behavior of Azide Ions on Platinum Electrodes

“…1, reaction [1] is proposed for the adsorption of N3-on platinum N~---~ Pt -N3"add + e- [1] Since the shift of the peak A of about 80 mV due to the pH change 2.6 is roughly half of the shift of the Hz generation potential of about 150 mV for the same pH change, approximately two protons may participate in the reduction at the peak A. 1, reaction [1] is proposed for the adsorption of N3-on platinum N~---~ Pt -N3"add + e- [1] Since the shift of the peak A of about 80 mV due to the pH change 2.6 is roughly half of the shift of the Hz generation potential of about 150 mV for the same pH change, approximately two protons may participate in the reduction at the peak A.…”

“…3 indicates that peak B is caused by the reaction product at peak A. 1, the following reaction [3] is proposed for the reduction at the peak B Pt = NH2~add + H ~ + 2e-~ Pt + NH3 [3] The reaction scheme consisting of [1], [2], and [3] does not contradict the result in Fig. From these results, together with the existence of the NI4_~ § oxidation peak at -0.2V in Fig.…”

“…Azide ion N3-is a typical pseudo-halide ion that produces ammonia by a photocatalytic reaction with water on a platinized TiO2 surface in aqueous solution (1). Therefore, it is interesting to investigate the electrochemical behavior of N3-on a Pt electrode.…”