Unveiling Carrier Dynamics in Periodic Porous BiVO₄ Photocatalyst for Enhanced Solar Water Splitting

Improved photocatalytic activities in highly ordered porous photocatalysts are often attributed to the larger surface area, higher light absorption, and suppressed charge recombination. Other underlying reasons for the improved charge transport, however, remain elusive at this stage. Herein, 3DOM BiVO₄ photocatalysts are examined to understand the carrier dynamics and their effects in photocatalytic water splitting. Quantum confinement arising from the ultrathin and crystalline wall upshifted its conduction band, enabling photocatalytic proton reduction to hydrogen gas under visible-light illumination. Time-resolved microwave conductivity spectroscopy reveals its ∼6 times higher charge mobility and longer charge diffusion length relative to the bulk counterpart. The long lifetime (∼360 ns) of 3DOM BiVO₄ with a power-law decay suggests the improved charge separation and the formation of shallow trapping states. Further investigation by Kelvin probe force microscope discloses a built-in electric field with upward band bending from the internal wall to the interconnection part of 3DOM BiVO₄.