Phase and morphology changes induced by acid treatment following alkaline reaction of mesoporous anatase: Effect of anions

► Mesoporous anatase in KOH solution at 90 °C decomposes into amorphous paste. ► The paste can be transformed to fibrous anatase or TiO2-B by mixing with inorganic acids. ► HCl causes the formation of TiO2-B at pH 1.2 and hexatitanate at pH 6.0-12.0. ► H2SO4 and HNO3 solutions cause the formation of anatase. ► H2SO4 and HNO3 solutions in the presence NaCl at pH 1.2 produce TiO2-B.