Single-crystalline, wormlike hematite photoanodes for efficient solar water splitting

Abstract

A hematite photoanode showing a stable, record-breaking performance of 4.32 mA/cm2 photoelectrochemical water oxidation current at 1.23 V vs. RHE under simulated 1-sun (100 mW/cm2) irradiation is reported. This photocurrent corresponds to ca. 34% of the maximum theoretical limit expected for hematite with a band gap of 2.1 V. The photoanode produced stoichiometric hydrogen and oxygen gases in amounts close to the expected values from the photocurrent. The hematitle has a unique single-crystalline “wormlike” morphology produced by in-situ two-step annealing at 550°C and 800°C of β-FeOOH nanorods grown directly on a transparent conducting oxide glass via an all-solution method. In addition, it is modified by platinum doping to improve the charge transfer characteristics of hematite and an oxygen-evolving co-catalyst on the surface.

Recent Progress in Energy‐Driven Water Splitting

“…[[qv: 172a,h]] On the other hand, the slow water oxidation reaction kinetics of hematite photoanode can be addressed by surface modification with cocatalysts (e.g. IrO 2 , Co 3 O 4 , Co‐Pi, Ni(OH) 2 ) 173. For instance, the most effective water oxidation cocatalyst, IrO 2 nanoparticles were coupled to the surface of hematite to significantly reduce the onset potential by 0.2 V.[[qv: 173b]] Likewise, Co 3 O 4 , Co‐Pi and Ni(OH) 2 prepared by electrodeposition or atomic layer deposition on hematite were developed as cheaper substitutes to noble metal oxides to reduce the overpotential of hematite photoanodes for water oxidation reaction.…”

Cobalt Phosphate Group Modified Hematite Nanorod Array as Photoanode for Efficient Solar Water Splitting

“…Works related to the nanostructure manipulating mainly focus on the nanorod/nanowire structure, which behaves as preferable structure for photoelectrocatalyst in solar water splitting [11,16,17]. Such morphology could satisfy both effective light harvest with the long optical path and excellent charge transport with the short diffusion distance.…”

An innovative photoelectrochemical lab device for solar water splitting

“…[7] More recently, a single photoelectrochemical device with Pt-doped hematite photoanode modified with Co-Pi catalyst produced a record-performance of 4.32 mA·cm -2 at 1.23 VRHE under simulated 1 sun (100 mW·cm -2 ). [8] A different approach for splitting water into hydrogen and oxygen consists of using aqueous suspensions of self-supported photocatalysts composed by semiconductor powders or colloidal (often a large band gap metal oxide) and a noble metal such Pt. [9] Even if these systems present the great advantage of enabling photolysis in a homogeneous phase without the need of both expensive transparent electrodes and directional illumination, they have a huge problem: the separation of the explosive mixture of hydrogen and oxygen is not easy, bringing safety concerns about these devices.…”