Two-dimensional Mixed Phase Leaf-Ti1-xCuxO2 Sheets Synthesized Based on a Natural Leaf Template for Increased Photocatalytic H2 Evolution

Two-dimensional (2D) leaf-TiO2 (LTiO2) nano sheets were synthesized using a natural leaf template. In addition, 2D mixed phase leaf-Ti1-xCuxO2 sheets (1CuLTiO(2)) were prepared by incorporating Cu ions (1wt%) into the LTiO2 lattice using a deposition-precipitation method followed by a calcination process. Structural microscopic and spectroscopic analyses demonstrated the generation of anatase and rutile surface-phase junctions as well as the combination of Cu ions with the disordered mesoporous leaf-TiO2 lattice. Hydrogen evolution reactions over 1CuLTiO(2) materials were performed using methanol as a sacrificial reagent under one sun illumination. LTiO2-750, synthesized by calcination at 750 degrees C, showed an absorption onset at 410nm, while LTiO2-550, synthesized by calcination at 550 degrees C, exhibited an onset at 387nm. Cu incorporation into the 1CuLTiO(2)-750 lattice, synthesized by calcination at 750 degrees C, led to the increase in the visible light absorption. Both the photocurrent and hydrogen yield via 1CuLTiO(2)-750 (apparent quantum yield, 4.9%) were higher than the respective values of 1CuLTiO(2)-550 (AQY=2.9%) synthesized by calcination at 550 degrees C, highlighting the importance of the surface-phase junction. The increased photocatalytic activity of 1CuLTiO(2)-750 was mainly assigned to the formation of surface-phase junctions, disordering mesoporosity, and 2D sheet morphology for fast charge carriers.