Architecture Dictates the Activity of Hollow TiO2 Nanospheres in Photocatalytic Solar Energy Conversion

Significant progress has been achieved in elucidating the relationship between the architecture of heterogeneous photocatalysts and their catalytic activity. Notably, it is recognized that hollow nanospheres exhibit superior catalytic activity compared with their filled nanoparticle counterparts. Yet, the impact of diameter and shell thickness on photocatalytic activity remains unclear. Here, we designed hollow TiO2 nanospheres with varying thicknesses and diameters. Our study reveals that disparities in catalytic activity, for processes such as H2 production, N2 reduction, or dye degradation, defy simple attribution to defects, surface facets, surface area, or variations in exciton lifetimes. Intriguingly, a decrease in catalytic activity was observed with an increase in the external diameter or shell thickness. The absorption and scattering of a single hollow nanosphere increase with particle diameter and shell thickness. However, at a given concentration, nanospheres with lower shell thickness and external diameter are in greater numbers, thus resulting in overall greater absorption and scattering for hollow nanospheres with lower diameter and diameter. We envision that this study will provide a foundation for the rational design of nanomaterials with enhanced photoactivity.