Viscosity effect of polyols on the growth of nanostructured titania photoanode for photoelectrochemical water splitting

The key role of viscosity of the anodizing electrolyte while fabricating anodic TiO2 nanostructures is evaluated by mixing ethylene glycol (EG) and triethylene glycol (TEG) with NH4F and water. Three-layer film structures are grown using EG and TEG mixtures of different ratios in fluoride-based aqueous electrolyte. The TiO2 nanostructure photoanodes fabricated in EG:TEG (1:3) mixture exhibit higher photoelectrochemical performance (689 μA cm-2 at 1.23 VRHE) in 1 M KOH than in pure EG and TEG electrolytes. The photoelectrochemical current density of TiO2 nanostructures remains high (∼730 μA cm-2) during the durability test under one sun solar simulated light at room temperature. The DFT calculations show that the stabilized environment around [Ti(OH)4(H2O)2] complex in the polyol mixture enhances the crystallinity of TiO2 anatase phase. This work emphasizes the role of viscosity of anodizing electrolyte to control the anodic TiO2 nanostructure formation to enhance photoelectrochemical water splitting and green H2 production.