Preparation of carbon-modified NTiO₂/ montmorillonite composite with high photocatalytic activity under visible light radiation

In this paper, the photocatalytic activity of nitrogen-doped TiO₂/montmorillonite composite (NTM) was successfully enhanced by modification with carbon. NTM was made by mixing a swelling clay solution with an N-doped TiO₂ solution prepared by hydrolysis of titanium tetraisopropoxide with urea. Carbon-modified Ndoped TiO₂/montmorillonite composite (CNTM) was obtained by grinding the dried NTM with EtOH for 1 h, followed by calcination at 250°C in the air for 2 h. Both NTM and CNTM exhibited visible light absorption in the UVvis spectrum in the same way as commercial NTiO₂ powder. Additionally, CNTM greatly extended the absorption edges to the visible light region. The photocatalytic performance of NTM and CNTM was evaluated using a degradation of bisphenol-A under visible light (>420 nm) radiation. Although the commercial TiO₂ powder showed less photocatalytic activity under visible light radiation, NTM, CNTM and commercial NTiO₂ powder showed high photocatalytic activity. The order of degradation performance was as follows: CNTM > commercial NTiO₂ powder > NTM. Since the TiO₂ content of CNTM is ca. 30 mass% by energy dispersive spectrum analysis, it was suggested that CNTM has extremely high visible light activity.