Photocatalytic performance of bipyramidal anatase TiO2 toward the degradation organic dyes and its catalyst poisoning effect

Abstract

It has been reported that bipyramidal anatase TiO2 with {101}-exposed facets (AT170) results in outstanding photocatalytic performance. However, its activity decayed significantly and comparatively lower than that of commercial P25 after 20 min. Further studies and calculations showed that the methylene blue (MB) degradation rate constants for AT170 were time dependent and decrease of k values with time. Besides, the results of XPS, EA and TEM could clearly elucidate that the active sites of catalysts were blocked by the carbon buildup and covered on the surface creating the metal-carbon bonding on the catalysts. These observation strongly implied the existence of the poisoning effect of AT170 during photocatalytic processes. Also, the surface area values of P25 and AT170 were found to be 46.83 and 3.56 m(2)/g respectively. It was suggested that the catalyst poisoning effect could be prevented or controlled by increasing the surface area of the catalyst. Besides of surface area, zeta potential was also found to be served as the important factor determining the photocatalytic performance toward organic dyes due to the attraction/repulsion of electrostatic interaction. The zeta potential values of P25 and AT170 were found to be - 3.8 and - 32.9 mV respectively, which can adsorb cationic MB dyes on the negative charged surface through attraction of electrostatic interaction successively enhancing the degradation performance. It strongly indicates that both surface area and zeta potential play vital roles in photocatalytic degradation toward organic dyes and affect the rate constants.