Simultaneous Improvement of Absorption and Separation Efficiencies of Mo:BiVO₄ Photoanodes via Nanopatterned SnO₂/Au Hybrid Layers

BiVO₄ has a thickness limitation because of carrier diffusion length; thus, the light-absorption efficiency is limited. To resolve this issue, we propose coating Mo:BiVO₄ on nanopatterned electrodes fabricated via direct-printing technology, which is the most suitable patterning technology for energy-related fields in cases where cost effectiveness is important. We designed two types of nanoelectrodes: nanocone (NC) and reverse NC (RNC). Nanopatterned electrodes mitigate the problems of the short carrier-diffusion length, allowing a larger amount of Mo:BiVO₄ to be coated. Also, the Au electrode acts as a back reflector, causing multiple light scattering. The nanopatterned electrode increases the carrier-separation efficiency and the light-absorption efficiency simultaneously owing to the larger amount of Mo:BiVO₄ and multiple light scattering. The photocurrent densities of the Au/SnO₂/Mo:BiVO₄ NC electrode, a corresponding RNC electrode, and a flat electrode were 1.53, 1.35, and 0.44 mA/cm², respectively, at 1.23 V_RHE under 1-sun illumination.