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

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 V_RHE 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.