Engineering the Morphology and Crystal phase of the 3D Hierarchical TiO2 with Excellent Photochemical and Photoelectrochemical Solar Water Splitting.

Owing to the unique advantages, hierarchical TiO 2 nanostructures have several advantages in solar fuel production. In this work, a single step approach has been demonstrated to control both crystal phase and morphology of TiO 2 with 3D urchin-like structure via a surfactant-free solvothermal route. The growth principle of 3D hierarchical structure with phase-engineered band-alignment, role of mixed solvent ratio H 2 O:HCl and reaction parameters are finely tuned and investigated systematically. An optimum percentage of anatase (41%) to rutile (59%) in the mixed phase TiO 2 (AR-2) shows an excellent photocatalytic H 2 generation activity of 5753 mumol g -1 after 5 h of irradiation with an apparent quantum yield of 20.9% at 366 nm and 4.5% at 420 nm. The superior performance of AR-2, attributed to efficient separation of charge carriers through phase-junction as apparent from the transient photocurrent ( i-t ) response and photoluminescence (PL) study. The 3D urchin-like pure rutile TiO 2 (R-1) composed of nanorods shows enhanced photocatalytic activity than pure anatase (A-1) and pure rutile TiO 2 nanoparticles, underlying the role of morphology. The best performing mixed phase 3D TiO 2 shows excellent durability up to 25 h and is further demonstrated to produce 3522 mumol g -1 of H 2 under natural sunlight highlighting its potential for long-term viable application.