Study on Precursor of Visible-Light-Active Titanium Oxide Photocatalyst Characterized by Temperature-Programmed Desorption-Mass Spectroscopy (TPD-MS)

Abstract

In this paper, we apply the temperature-programmed desorption (TPD) method combined with mass spectrometric (MS) analysis to characterize the hydrolysis products of Ti (SO4) 2 (SHy-NH) and TTIP (AHy-NH) with an NH3 aqueous solution, that can be vis-active photocatalysts when they are calcined at suitable temperatures in air. We find that H2O is the only product that exists below 100C. Beyond 100C, however, NH3 desorption begins and showsits maximum strength at approximately 200C. This desorption continues to near 450C ; we know this because NH+ (m/z 15) can still be detected beyond 400C. In the case of SHy-NH, desulfurization commences at approximately 400C, since SO2+ (m / z 64) , which cannot be removed by the washing process, is detected. Considering these results, the emergence of vis-activity during the process of hydrolysis product calcination appears to be concerned with the desorption of volatile species from the polycrystalline titanium oxide structure. We propose that this desorption leads to oxygen deficiency, as confirmed by XPS.