Particle aggregation behavior during photocatalytic ethanol reforming reaction and its correlation with the activity of H₂ production

When dispersed in water, nanoscale photocatalysts tend to aggregate due to their high surface energy. Complex interaction of the incident light with the aggregated particles is expected due to their comparable length scales. In this study, the aggregation behavior of TiO₂ nanoparticles during photocatalytic ethanol reforming was investigated by the dynamic light scattering (DLS). DLS results demonstrated that UV light can significantly inhibit the aggregation of TiO₂ compared to that under visible light or in the dark. Considering that the ethanol photo-reforming over TiO₂ can only occur under UV light, we correlated the significant light-induced particle aggregation with the photocatalytic reactions. Three different aggregation degrees for TiO₂ were employed to study the effect of aggregation on its activity for photocatalytic H₂ production. The H₂ production is found to decrease with the increase of aggregates in the suspension. Our results should be of great value for the understanding of the dynamics in photocatalyst particle suspension during the photocatalytic reaction. More importantly, it is supposed that one can improve the activity of the photocatalytic reaction by controlling the particle aggregation through carefully adjusting the external physical fields such as the intensity of the incident light at certain wavelength interval.