A systematic study of post-activation temperature dependence on photoelectrochemical water splitting of one-step synthesized FeOOH CF photoanodes with erratically loaded ZrO2

Abstract

With regard to both the activity and stability of photoelectrode materials, in this study, a hematite cauliflower-like structure with irregularly loaded ZrO₂ (ZrO₂–Fe₂O₃ CF) was prepared from as-deposited samples. The effect of post-synthetic treatments such as systematic high-temperature heating at various temperatures (650, 700, 750, and 800 °C) for 10 min, followed by rapid cooling at room temperature (quenching) on interfacial properties and photoelectrochemical performance was investigated in detail. The photoelectrochemical performances of the quenched ZrO₂–Fe₂O₃ CF samples were compared to those of conventionally synthesized hematite nanorod photoanodes quenched from 800 °C (PQ800). Interestingly, ZrO₂–Fe₂O₃ CF photoanodes quenched from 650 °C exhibited 0.62 mA cm⁻² photocurrent density at 1.23 V vs. RHE, which was 14 times higher than that of the conventionally synthesized hematite quenched from 650 °C (PQ650). Furthermore, ZrO₂–Fe₂O₃ CF photoanodes quenched from 800 °C revealed a photocurrent density of 1.66 mA cm⁻² at 1.23 V vs. RHE (twice that of PQ800) and improved charge separation efficiencies of η_bulk = 15.6% and η_surface = 94.6%, respectively. The XPS and HRTEM results also confirmed the irregular ZrO₂ loading on the surface of Fe₂O₃ CF. A possible formation and charge transfer mechanism of ZrO₂–Fe₂O₃ CF was proposed based on a series of temperature-dependent experiments.