Recent progress in iron oxide based photoanodes for solar water splitting

Abstract

Solar assisted water splitting in a PEC is an attractive concept to store solar energy as hydrogen fuel but the effective efficiency of the process is too low for it to be a serious contender for commercialization. The most important component of the PEC to achieve efficient water splitting is a photo active anode that could effectively absorb photons and deliver holes for the oxygen evolution reaction. Hematite has many attributes that make it a good candidate material for a photoanode but it also has some deficiencies. This article reviews the state-of-the-art hematite-based photoanodes, with special emphasis on attempts made by researchers to overcome its drawbacks. The numerous research reports are categorized under distinct strategies such as nanostructuring, elemental doping, surface passivation, cocatalyst application, conducting template incorporation and heterostructures which are possible pathways to improve the performance of hematite. The scientific understandings of the operating mechanisms for each strategy are systematically presented and discussed, and the improvements achieved by different approaches are compared. Some cutting-edge strategies, such as heterojunctions, could be important and hematite based heterostructures are discussed. A developing interest in an emerging material, Fe 2 TiO 5 is also discussed and some of the important benefits of this material are presented. Finally, the importance of scaling up the technology is discussed and attention is drawn to some possible challenges on scaling up. The paper concludes with some future technology directions and prospects for hematite-based photoanodes.

PrFeO3 Photocathodes Prepared Through Spray Pyrolysis

“…There is a range of metal oxide semiconductors capable of driving PEC reactions in addition to the typical TiO 2 and SrTiO 3 semiconductors . Hematite (α‐Fe 2 O 3 ) for example has been well studied as a photoanode but commonly suffers from high levels of electron‐hole recombination . Additionally, BiVO 4 and WO 3 have been well studied .…”

High Throughput Discovery of Effective Metal Doping in FeVO4 for Photoelectrochemical Water Splitting

“…with high stability for PEC water oxidation are often used as photoanodes. [ 8–19 ] However, the application of these materials into commercial devices is still limited by either their bandgaps that are often too large or their poor charge carrier dynamics.…”

Synthesis of Plasmonic Photocatalysts for Water Splitting

“…Another chemical compound, iron oxide, especially in the form hematite (α-Fe 2 O 3 ), has been recognized as a promising photocatalyst, since it is inexpensive, non-toxic, in plentiful supply, and has an appealing band gap (~2.1 eV) for sunlight absorption. The reason why α-Fe 2 O 3 has not been used practically so far is that it has several critical drawbacks such as short lifetime of charge carriers (<10 ps) and short hole diffusion length (2-4 nm) compared to deep light penetration depth (~120 nm) [45][46][47][48][49]. It needs to be available as a nanoparticle or thin film to enable the most generated holes to reach the surface, while a large dimension is required to effectively absorb incident light [50][51][52].…”