Two‐dimensional Mixed Phase Leaf‐Ti 1‐ x Cu x O 2 Sheets Synthesized Based on a Natural Leaf Template for Increased Photocatalytic H 2 Evolution

Two‐dimensional (2D) leaf‐TiO 2 (LTiO 2 ) nano sheets were synthesized using a natural leaf template. In addition, 2D mixed phase leaf‐Ti 1‐ x Cu x O 2 sheets (1CuLTiO 2 ) were prepared by incorporating Cu ions (1 wt %) into the LTiO 2 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‐TiO 2 lattice. Hydrogen evolution reactions over 1CuLTiO 2 materials were performed using methanol as a sacrificial reagent under one sun illumination. LTiO 2 ‐750, synthesized by calcination at 750 °C, showed an absorption onset at 410 nm, while LTiO 2 ‐550, synthesized by calcination at 550 °C, exhibited an onset at 387 nm. Cu incorporation into the 1CuLTiO 2 ‐750 lattice, synthesized by calcination at 750 °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 °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.