Morphology-Engineered Hematite Photoanode for Photoelectrochemical Water Splitting

The photoelectrochemical (PEC) water oxidation reaction on hematite photoanodes poses challenges, notably the limited hole diffusion length and poor electrical properties. This study addresses these issues by creating a highly porous structure through the Kirkendall effect at the interface of the overlayer and hematite precursor. By fabricating branched hematite precursors, we produced a highly nanoporous structure with an average strut diameter below 10 nm between pores. Coupled with morphological engineering, doping from the overlayer enhances the electrical properties of hematite, and the selection of an appropriate dopant (overlayer) was determined through density functional theory. The optimized photoanode with a NiFe(OH)x cocatalyst displayed a maximum photocurrent density of 5.1 mA cm–2 at 1.23 VRHE, a 3.2-fold increase compared to the reference. The enhancement results from the nanoporous structure combined with optimal doping conditions, representing a significant step in improving the low PEC performance of hematite-based photoanodes.