Hydrogen Peroxide-Mediated Synthesis of Triphasic Titanium Dioxide: Impact of Phase Composition on PEC Water Oxidation Performance.

A series of triphasic TiO2 materials comprising anatase, rutile, and brookite (A/R/B) were synthesized via a peroxide-mediated inverse micelle route. The A/R/B ratios were systematically tuned by varying the concentration of hydrogen peroxide (H2O2). Control experiments conducted to isolate the specific role of H2O2 as a phase-directing agent indicate that a synergistic peroxide-acidic environment is required for the formation of triphasic TiO2. Photoelectrochemical (PEC) performance was evaluated using linear sweep voltammetry (LSV), applied bias photon-to-current efficiency (ABPE), and transient photocurrent response. All the triphasic samples showed enhanced PEC performance compared to pure-phase anatase. 7-HP-TiO2 exhibited the highest ABPE and photocurrent density of 58 μA cm-2 at 1.23 V vs RHE and a peak ABPE of 0.046% at 0.37 VRHE among the series of materials tested. Photoluminescence spectroscopy (PL) and electrochemical impedance spectroscopy (EIS) were also employed to elucidate the influence of phase composition on charge separation and transfer efficiency. The enhanced activity of 7-HP-TiO2 was attributed to the synergistic effect of the A, R, and B phases within the material. An optimal composition of 56% A, 9% R, and 35% B promotes efficient electron-hole separation and charge transfer efficiency, thereby maximizing photocurrent density.