Effect of Sn valence state in the in situ growth of FeOOH precursor on the performance of the α-Fe2O3 photoanode

Abstract

Sn-doped Fe₂O₃ photoanodes are fabricated by employing a tin salt precursor with different Sn valence states, and Sn⁴⁺ ions are incorporated in the Fe₂O₃ photoanode. The valence state of Sn ions in hydrothermal precursors is found to exert a great effect on the phase structure, morphology, optical, electronic and PEC properties of the Sn-doped Fe₂O₃ photoanode. The optimized Sn²⁺–Fe₂O₃ photoanode exhibits a remarkable photocurrent density of 1.894 mA cm⁻² at 1.23 V vs. RHE, ABPE of 0.1031% and incident photon-to-current efficiency (IPCE) of 16.1% at 1.23 V vs. RHE, which is the largest value yet reported. This excellent PEC performance of the Sn²⁺–Fe₂O₃ photoanode is attributed to a unique nanopore structure with high-density, which brings about strong visible light absorption, increased ECSA, well-preserved morphology and effective Sn doping. As a result, both charge injection efficiency and charge separation efficiency are improved.