Significant Aggregation-Enhanced Carrier Separation in Nanoscopic Catalysts Heterojunction Stacks.

Nanoscopic heterojunction stacks are prevalent in nature as well as in artificial material systems, such as the nanoscopically blended components in soil or artificial catalytic layers on device surfaces. Despite the enormous attention placed on studying individual heterojunctions, the advantageous catalytic performance of heterojunction aggregates has not been recognized. In this study, we employ the ordered N-doped TiO2 nanosheets and Au nanoparticle heterojunction multilayers obtained by a layer-by-layer technique to investigate the functional merits stemmed from heterojunction aggregates. The study demonstrates that nanoscopic heterojunction stacks promote the internal electric field that stemmed from charge separation and boost carrier separations. The aggregate-enhanced carrier separation can be harnessed in chemical conversions. The enhancement effect is influenced by both the dimensions of the entire aggregates as well as the dimensions of the nanoscopic building units. We expect the study to promote the understanding of heterojunction catalysts and corresponding matter conversion from the individual particulate level to the nanoscopic aggregate level and facilitate better harnessing of the photovoltaic effects or catalytic power in nanoscopic heterojunction aggregates.