Hematite photoanodes prepared by particle transfer for photoelectrochemical water splitting

Abstract

A hematite (α-Fe2O3) photoanode for O2 evolution is usually prepared as a thin film on a conductive substrate like a fluorine-doped tin oxide/glass. Such a conductive substrate is not resistive...

Roles of Surface States in Cocatalyst-Loaded Hematite Photoanodes for Water Oxidation

“…The key to enhance this reaction is improving its half-reaction for water oxidation over a photoanode . Hematite (α-Fe 2 O 3 ) has been widely investigated for this purpose because this material is wide-spectrum-responsive (λ < 600 nm), chemical-stable, element-abundant, and nontoxic. , For example, Wang et al fabricated various structured α-Fe 2 O 3 photoanodes with a relatively low onset potential for water oxidation and further combined them with Si photocathodes for unbiased water splitting. − Recently, our group applied a particle-transfer method to fabricate a scalable particulate α-Fe 2 O 3 photoanode, showing a surprisingly low onset potential at 0.6 V (vs reversible hydrogen electrode, RHE) at nearly neutral pH . We further employed this photoanode for unbiased water splitting with the combination of a particulate Ga-doped La 5 Ti 2 Cu 0.9 Ag 0.1 O 7 S 5 photocathode in a parallel cell.…”

“…5−8 Recently, our group applied a particle-transfer method to fabricate a scalable particulate α-Fe 2 O 3 photoanode, showing a surprisingly low onset potential at 0.6 V (vs reversible hydrogen electrode, RHE) at nearly neutral pH. 9 We further employed this photoanode for unbiased water splitting with the combination of a particulate Ga-doped La 5 Ti 2 Cu 0.9 Ag 0.1 O 7 S 5 photocathode in a parallel cell. However, the performance of the above PEC cells for water splitting is still far behind the target for cost-effective hydrogen generation, 10 especially due to the limited performance on the α-Fe 2 O 3 photoanode side.…”

Photocorrosion of Hematite Photoanodes in Neutral and Alkaline Electrolytes

“…Several works have revealed the increased photocorrosion of Fe 2 O 3 in acidic electrolytes. ,− However, detailed information about the rates of Fe dissolution and its dependence on the electrolyte species and pH is still missing. This knowledge is of relevance since Fe 2 O 3 has been used to construct photoanodes to drive the PEC water splitting in mild conditions (neutral electrolytes). − Recently, coupling on-line inductively coupled plasma mass spectrometry (ICP-MS) to PEC measurements has provided novel insights into the light-triggered photodegradation of WO 3 , BiVO 4 , and TiO 2 photoanodes, − proving to be an excellent approach to reveal different degradation pathways.…”

Enhanced Photoelectrocatalytic Water Splitting in Bi2Mo1–xWxO6 Solid Solutions: Understanding the Atomic Level Mechanism from the Experimental and First-Principles Approach

“…Photoelectrocatalytic (PEC) water splitting is a clean and viable technology to split water molecules into hydrogen and oxygen using semiconductor photoelectrodes. The overall PEC efficiency of photoelectrodes depends on several factors such as visible light absorption, charge transfer dynamics, and the lifetime of the charge carriers. − In PEC water splitting, water oxidation is a sluggish process and is considered a rate-determining step; therefore, the development of a photoanode is a crucial part in PEC water splitting. − Mostly, TiO 2 -based photoanodes were investigated in the PEC process due to their availability, stability, and harmlessness, but their wide bandgap (∼3.2 eV) makes them inefficient for harvesting solar energy; therefore, researchers focus on the development of semiconductor materials with a narrow bandgap (<3.0 eV). Recently, bismuth-based semiconductor materials such as BiOX (X = I, Cl, Br) , and Bi x M y O z (M = V, Mo, W, Fe) have attracted a lot of attention in the field of PEC water splitting due to their narrow bandgap, in which the valence band consisting of O-2p and Bi-6s orbitals offers a well-dispersed valence band and facilitates the mobility of the photogenerated holes for water oxidation. − Compared to BiVO 4 , Bi 2 MoO 6 and Bi 2 WO 6 have a higher positive valence band edge, and hence, they can expect facile water oxidation by photogenerated holes in PEC water splitting.…”