Co(OH)2/BiVO4 photoanode in tandem with a carbon-based perovskite solar cell for solar-driven overall water splitting

Abstract

BiVO4 as a promising candidate photoanode material for PEC water splitting has been paid much attention due to its low cost, nontoxicity, high stability and narrow band gap energy of 2.4 eV. However, owing to its short carrier diffusion length and poor charge separation consequence, the achieved efficiency of the BiVO4 photoanode is still limited. Herein, we addressed this issue by loading Co(OH)2 onto as-prepared BiVO4 to fabricate Co(OH)2/BiVO4 heterojunction photoanode via a simple solution impregnation method, in which Co(OH)2 as a modifier can increase interface charge separation efficiency from 44% of BiVO4 to 92% of Co(OH)2/BiVO4. As a result, the water-splitting photocurrent density was significantly enhanced from 1.57 mA/cm2 of BiVO4 to 4.52 mA/cm2 of Co(OH)2/BiVO4 at 1.23 V vs. RHE under 1-sun illumination. Further, the Co(OH)2/BiVO4 photoanode was assembled in tandem with a single sealed carbon-based PSC, and the resulting PV-PEC device showed a high STH efficiency of 4.6% and decent stability. The produced H2 and O2 gases were determined as ∼68 μmol/cm2/h and ∼34 μmol/cm2/h, respectively, corresponding to the 2:1 ratio of water splitting reaction with a faradaic efficiency of ∼98%.