An Innovative Measurement for Testing the Nanocatalyst Degradation Efficiency of NH3

Abstract

This study develops a low-cost, fast and innovative measurement method for testing the efficiency of photocatalysts in the degradation of gaseous concentrations. In the past, photocatalyst tests of catalyst response to gases mainly relied on measurement with either GC/MS (Gas Chromatography/Mass Spectrometer) or FTIR (Fourier Transform Infrared Spectroscopy), to monitor the reaction process. However, these two instruments are very expensive, and the processes are complicated and time-consuming. The major devices of the measurement method developed by this study are UV/VIS spectrophotometer and quartz cuvettes. The experimental procedures are not only simple but fast. In the experiment, a gas of a specific concentration is first injected into an enclosed quartz cuvette. The cuvette is then placed in the UV/VIS spectrophotometer to carry out tests to obtain an absorption spectrum. Thus, a calibration curve of UV light absorbance intensity vs. various gaseous concentrations can also be obtained using the same method. The degradation efficiency of the different photocatalysts is to be measured. Quartz plates are coated with two different types of TiO2 nanocatalysts. The coated plates are then placed in separate cuvettes. After injecting NH3 into a quartz cuvette, the cuvette is then put under the UV light irradiation to perform the degradation experiment. Afterwards, the cuvette is transferred to the UV/VIS spectrophotometer for testing. The absorbance intensity of the absorption spectra is then compared with the calibration curves. Based on the change of the gaseous concentration, the degradation efficiency of the photocatalyst is determined. The experimental results reveal that the self-made TiO2 nanocatalyst has excellent degradation efficiency towards NH3. When NH3 is exposed to UV irradiation for 60 minutes, the gaseous concentration can be reduced to 10.35% of the original concentration. However, the commercial TiO2 nanocatalyst can only reduce the gaseous concentration to 50.2% of the original concentration. In addition, the degradation reaction rate constant of the self-made TiO2 nanocatalyst towards NH3 is as high as 0.029 min−1.