Abstract

The deficiencies in the separating photogenerated electrons/holes in the bulk and driving them across the interface of semiconductor/electrolyte are the major issues that limit the photoelectrochemical (PEC) performance of hematite (α-Fe2O3) photoelectrodes. In this work, a Z-scheme planar heterostructure of n-Si and α-Fe2O3 was designed and constructed by a facial ion-beam assisted deposition technique with the best match of the optical absorption depth, the film thickness and the space charge region thickness. A thin ITO layer (~10 nm) was sandwiched in-between in order to achieve the optimal carrier separation capacity, and the IrOx cocatalysts were introduced to improve the surface reaction kinetics. The results demonstrate a significant improvement of α-Fe2O3 PEC performance: a photocurrent density was improved to 1.987 mA cm−2 (1.23 V vs. RHE), ~100 times larger than that of bare α-Fe2O3, whereas the onset potential was dropped by 0.57 V over unmodified α-Fe2O3, due to the enhanced photovoltage by n-Si and the improved surface reaction kinetics. This work advances planar α-Fe2O3-based photocatalytic cells to a new performance record for water splitting.

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