Spontaneous Electric Field Directionality in One-Dimensional Semiconductors: Key to Efficient Charge Migration, Minimizing Recombination, and Enhancing Photocatalytic Performance

Photocatalytic water splitting holds great promise as a solution to the global energy crisis, but its practical application is hindered by low efficiency, primarily due to bulk charge recombination. One strategy to mitigate this issue is the application of a spontaneous polarization electric field, which can accelerate charge migration and reduce the level of recombination. However, previous studies have mainly focused on enhancing the strength of the polarization field, while the role of directional alignment in anisotropic semiconductors remains less explored. In this work, we present a comparative study of two isostructural borates, CsNbOB2O5 (CNBO) and CsTaOB2O5 (CTBO), both of which act as one-dimensional (1D) conductive semiconductors. Charge generation, separation, and migration occur within the corner-sharing NbO6 chains. Despite their similar structures, the local dipole moments of [NbO6] and [TaO6] are different. CNBO shows an optimal alignment of the spontaneous electric field, which drives charge carriers along separate paths and opposite directions, minimizing recombination and yielding an apparent quantum yield (AQY) of 22.28%, among the highest reported for micron-sized photocatalysts. CTBO, in contrast, demonstrates a significantly lower AQY of 1.71%, underscoring the critical role of electric field directionality. This study suggests that 1D conductive semiconductors hold substantial potential in photocatalysis by facilitating efficient charge separation and migration through spatially confined, directionally aligned electric fields.