Self-dispersion of photocatalysts at oil-water interface accelerates H2O2 production and separation

Abstract

Enhancing the efficiency of photocatalytic charge transfer for H2O2 production and in situ separation of H2O2 from aqueous suspension are crucial, especially when sacrificial agents are involved, for the advancement of this environmental-friendly process. In this study, we propose that the production and separation of H2O2 can be significantly enhanced at a self-assembled tri-phase system (water/photocatalyst/benzyl alcohol) compared to the suspension system. To prove this, we have employed titania nanotube (TNT) as a representative photocatalyst with efficient oxygen adsorption and modified it with organic ligand (octadecyl phosphate, OPA) and nickel species to modulate its hydrophobicity and dispersity at the interface, resulting in improved H2O2 yield. The modified TNT photocatalyst demonstrates efficient H2O2 production reaching a concentration of 5.1 mM after 75 mins under optimized conditions and an initial rate of 7500 μmol/g/h within first 6 h that even exceeding reported noble metals modified TiO2 photocatalysts. This enhanced activity is attributed to multiple effects including homogeneous dispersion of photocatalyst at the oil-water interface, efficient O2 adsorption and transfer, separated redox reactions at different phases, timely diffusion of H2O2 into bulk aqueous solution, and potential solvent-induced polarization effect on charge transfer, which result from the special oil-water interface that stabilizing photocatalysts and inducing photocatalytic O2 reduction. As proof-of-concept demonstrations show successful photosynthesis of H2O2 using natural solar light followed by utilizing the generated pure H2O2 solution for bacteria inactivation, indicating that interfacial photocatalytic systems offer promising potential for green H2O2 synthesis and application.