Strain-induced charge delocalization achieves ultralow exciton binding energy toward efficient photocatalysis

Abstract

The exciton effect is commonly observed in photocatalysts, where substantial exciton binding energy (E_b) significantly hampers the efficient generation of photo-excited electron–hole pairs, thereby severely constraining photocatalysis. Herein, we propose a strategy to reduce E_b through strain-induced charge delocalization. Taking Ta₂O₅ as a prototype, tensile strain was introduced by engineering a crystalline/amorphous interface, weakening the interaction between Ta 5d and O 2p orbitals, thus endowing a delocalized charge transport and significantly lowering E_b. Consequently, the E_b of strained Ta₂O₅ nanorods (s-Ta₂O₅ NRs) was reduced to 24.26 meV, below the ambient thermal energy (26 meV). The ultralow E_b significantly enhanced the yield of free charges, resulting in a two-fold increase in carrier lifetime and surface potential. Remarkably, the hydrogen evolution rate of s-Ta₂O₅ NRs increased 51.5 times compared to that of commercial Ta₂O₅. This strategy of strain-induced charge delocalization to significantly reduce E_b offers a promising avenue for developing advanced semiconductor photoconversion systems.