Key Strategies to Advance the Photoelectrochemical Water Splitting Performance of α‐Fe₂O₃ Photoanode

Abstract

The last few decades’ extensive research on the photoelectrochemical (PEC) water splitting has projected it as a promising approach to meet the steadily growing demand for cleaner and renewable energy in a sustainable and economically viable fashion. Among many potential photocatalysts, hematite (α‐Fe2O3) emerges as a highly promising photoanode material with favorable characteristics including visible light absorption (a suitable band gap energy), earth abundance, chemical stability, and low cost. A pronounced disadvantage of α‐Fe2O3 is its low photovoltage together with an extremely short hole diffusion length and a low electrical conductivity, which limit its PEC water oxidation performance. To make α‐Fe2O3 as a viable photocatalyst for PEC water splitting, one needs to rectify these unfavorable characteristics of α‐Fe2O3 by elaborated multiple modifications. In this review article, we introduce various modification strategies of hematite with emphasis on surface modifications to achieve low onset potential as well as high photocurrent approaching the theoretical value for solar water splitting.

Photoelectrochemical Sensing of Hydrogen Peroxide on Hematite

“…The PEC properties of our hematite surfaces were also assessed by photocurrent spectroscopy. The results obtained at 0.7 V are shown in a Tauc plot (inset of Figure c) which reveals that the photoelectrochemical bandgap of our material is 2 eV, in good agreement with the reported values for hematite . Next, we explored the possibility of using these surfaces for H 2 O 2 PEC sensing in the 3D printed cell (Figure a) under illumination at a constant potential of 0.7 V. After equilibration of the electrochemical signal, micro volumes of H 2 O 2 were sequentially injected into the cell and the current was simultaneously recorded.…”

“…Hematite (α‐Fe 2 O 3 ) is a promising photoanode material due to its great abundance, low‐cost, chemical stability and its high theoretical photoconversion efficiency . Nevertheless, it also has a short excited‐state lifetime and a small hole diffusion length.…”

“…The results obtained at 0.7 V are shown in a Tauc plot (inset of Figure 2c) which reveals that the photoelectrochemical bandgap of our material is 2 eV, in good agreement with the reported values for hematite. [41,42] Next, we explored the possibility of using these surfaces for H 2 O 2 PEC sensing in the 3D printed cell (Figure 2a sequentially injected into the cell and the current was simultaneously recorded. As shown in Figure 2c, the photocurrent increased with the injected volume, allowing for instantaneous sensing of the H 2 O 2 concentration.…”

“…Hematite (α-Fe 2 O 3 ) is a promising photoanode material due to its great abundance, low-cost, chemical stability and its high theoretical photoconversion efficiency. [41,42] Nevertheless, it also has a short excited-state lifetime and a small hole diffusion length. This is a severe drawback for energy-related applications [41,42] but can be a great advantage for the design of PEC sensor arrays activated by micrometer-sized spots of light.…”

“…[41,42] Nevertheless, it also has a short excited-state lifetime and a small hole diffusion length. This is a severe drawback for energy-related applications [41,42] but can be a great advantage for the design of PEC sensor arrays activated by micrometer-sized spots of light. [15,17] Hematite photoanodes have been previously employed for the PEC sensing of biological macromolecules, [43,44] neurotransmitters, [17] endocrine disruptors, [45,46] glucose, [25,44] inorganic pollutants, [47] and metal cations.…”