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 (Eb) significantly hampers the efficient generation of photo-excited electron-hole pairs, thereby severely constraining photocatalysis. Herein, we propose a strategy to reduce Eb 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 Eb. Consequently, the Eb of strained Ta2O5 nanorods (s-Ta2O5 NRs) was reduced to 24.26 meV, below the ambient thermal energy (26 meV). The ultralow Eb 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 Eb offers a promising avenue for developing advanced semiconductor photoconversion systems.