Solution-Processed, Antimony-Doped Tin Oxide Colloid Films Enable High-Performance TiO₂ Photoanodes for Water Splitting

Abstract

Photoelectrochemical (PEC) water splitting and solar fuels hold great promise for harvesting solar energy. TiO2-based photoelectrodes for water splitting have been intensively investigated since 1972. However, solar-to-fuel conversion efficiencies of TiO2 photoelectrodes are still far lower than theoretical values. This is partially due to the dilemma of a short minority carrier diffusion length, and long optical penetration depth, as well as inefficient electron collection. We report here the synthesis of TiO2 PEC electrodes by coating solution-processed antimony-doped tin oxide nanoparticle films (nanoATO) on FTO glass with TiO2 through atomic layer deposition. The conductive, porous nanoATO film-supported TiO2 electrodes, yielded a highest photocurrent density of 0.58 mA/cm(2) under AM 1.5G simulated sunlight of 100 mW/cm(2). This is approximately 3× the maximum photocurrent density of planar TiO2 PEC electrodes on FTO glass. The enhancement is ascribed to the conductive interconnected porous nanoATO film, which decouples the dimensions for light absorption and charge carrier diffusion while maintaining efficient electron collection. Transient photocurrent measurements showed that nanoATO films reduce charge recombination by accelerating transport of photoelectrons through the less defined conductive porous nanoATO network. Owing to the large band gap, scalable solution processed porous nanoATO films are promising as a framework to replace other conductive scaffolds for PEC electrodes.

A colloidoscope of colloid-based porous materials and their uses

“…Additional functional properties can be introduced to the inverse opal matrix by various surface modification techniques. The interconnected porosity enables the entire surface to be modified uniformly, for example using atomic layer deposition (ALD) [65][66][67][68][69][70][71][72] or electrodeposition 26,[73][74][75][76] techniques. The matrix material can also be conveniently chosen to allow for simple and reliable introduction of a rich variety of surface functionalities at a molecular level, for example via silane chemistry.…”

Water Splitting Processes on Mn4O4 and CaMn3O4 Model Cubane Systems

“…The water nucleophilic attack generally occurs between water molecules between Ca and the dangling Mn atom in the OEC. [20][21] The electron density at the oxyl oxygen bound to the Mn atom, which is 6 attacked by the nucleophilic water bound to the Ca atom, is reduced by the arginine residue nearby. 20 The oxyl-oxo coupling process in the OEC generally happens between an oxyloxygen at the dangling Mn and an oxo-oxygen at the corner of the cubane core.…”

“…5 TiO 2 has advantages in that it is cheap and non-toxic, but it has serious intrinsic shortcomings due to a wide band gap (3.0 eV for rutile and 3.2 eV for anatase); thus, it requires UV photons that account for less than 5% of the solar spectrum. 6 Metal oxide complexes have a high potential to be useful water splitting catalysts. Among them is RuO 2 (sometimes mixed with IrO 2 ), which is known as the best inorganic photocatalyst because it shows high efficiency for water splitting; however, the biochemical process in green plants, cyanobacteria, and algae performs more efficiently.…”

Perspective—A Brief Perspective on the Fabrication of Hierarchical Nanostructure for Solar Water Splitting Photoelectrochemical Cells

“…Likewise, the deposition process was naturally imported to make hierarchical nanostructure in terms of formation thin film structure on the metal oxide nanostructure. The deposition process was conducted by using various vacuum-based equipment such as atomic layer deposition (ALD), [40][41][42][43] chemical-vapor deposition, 21 E-beam evaporator, 44,45 pulsed laser deposition (PLD) 46,47 and sputtering 48 on the metal oxide nanostructures. By this way, a robust and dense thin film structure was accurately formed from only several nanometers to tens of nanometers onto the metal oxide nanostructure, obtained hierarchical nanostructure by controlling deposition processing conditions.…”