Abstract
This study addresses challenges in photoelectrochemical (PEC) water oxidation on hematite photoanodes, with a focus on overcoming the limited hole diffusion length (~4 nm) and poor electrical properties. To achieve this, an efficient overlayer is integrated onto the branched structure, generating a highly porous architecture by leveraging additional reaction interfaces exploiting the Kirkendall effect. This phenomenon occurs during high-temperature annealing, particularly at the interface of the overlayer and Ti-FeOOH (hematite precursor), utilizing distinct diffusion rates of metal atoms. By introducing additional interfaces on the hematite precursor surface, porosity and pore size are effectively controlled, resulting in a highly nanoporous structure. Through morphological engineering, the overlayer facilitates heteroatom diffusion (doping) into the hematite lattice, thereby promoting facile charge transport. The overlayer material selection is guided by density functional theory calculations. The resulting optimized photoanode, combined with an efficient cocatalyst (NiFe(OH)x), exhibits a maximum photocurrent density of 5.1 mA cm-2 at 1.23 V vs. RHE, marking a 3.2-fold increase compared to the reference hematite photoanode. This enhancement is attributed to the highly nanoporous structure and optimal doping. Thus, this study represents a significant advancement in enhancing the PEC performance of hematite-based photoanodes for future applications.
Published Version
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