Layer-by-Layer Molecular Assemblies for Dye-Sensitized Photoelectrosynthesis Cells Prepared by Atomic Layer Deposition

Abstract

In a dye sensitized photoelectrosynthesis cell (DSPEC), the relative orientation of the catalyst and chromophore plays an important role in determining the device efficiency. Here we introduce a new, robust atomic layer deposition (ALD) procedure for the preparation of molecular chromophore-catalyst assemblies on wide bandgap semiconductors. In this procedure, solution deposited, phosphonate derivatized metal complexes on metal oxide surfaces are treated with reactive metal reagents in the gas phase by ALD to form an outer metal ion bridging group, which can bind a second phosphonate containing species from solution to establish a R-PO-O-M-O-PO-R type surface assembly. With the ALD procedure, assemblies bridged by Al(III), Sn(IV), Ti(IV), or Zr(IV) metal oxide units have been prepared. To evaluate the performance of this new type of surface assembly, intra-assembly electron transfer was investigated by transient absorption spectroscopy, and light-driven water splitting experiments under steady-state illumination were conducted. A SnO bridged assembly on SnO/TiO core/shell electrodes undergoes light-driven water oxidation with an incident photon to current efficiency (IPCE) of 17.1% at 440 nm. Light-driven water reduction with a ruthenium trisbipyridine chromophore and molecular Ni(II) catalyst on NiO films was also used to produce H. Compared to conventional solution-based procedures, the ALD approach offers significant advantages in scope and flexibility for the preparation of stable surface structures.

Solar H2 generation in water with a CuCrO2 photocathode modified with an organic dye and molecular Ni catalyst

“…Nanostructuring of the surface would ensure higher loadings of dye and catalyst species, enhancing both stability and activity in the future. Alternate methods such as atomic layer deposition (ALD) 52 , 81 – 83 or polymeric assembly 84 – 87 could also be employed as additional stabilisation methods.…”

A stable dye-sensitized photoelectrosynthesis cell mediated by a NiO overlayer for water oxidation

“…1 (32,33). Preparation and characterization of nanoITO and SnO 2 /TiO 2 core/shell structures followed known literature procedures (34,35). In the current experiments, 4-μm-thick films of SnO 2 (composed of 15-nm nanoparticle) on FTO electrodes were coated with a 5-nm layer of TiO 2 to give the core/shell structures.…”

“…After drying in air, the FTOjSnO 2 /TiO 2 j-RuP 2+ slides were placed in an ALD chamber. The temperature in the ALD chamber was held at 150°C under conditions where the adsorbed molecules were known to be stable during ALD deposition conditions (34). The added metal oxide overlayer of 20 cycles NiO provides new binding sites for additional molecules on the surface.…”

Stabilized photoanodes for water oxidation by integration of organic dyes, water oxidation catalysts, and electron-transfer mediators

“…Photoelectrochemical Water Oxidation. Water oxidation was explored in core/shell nanoparticle SnO 2 /TiO 2 films with the core/shell structure assisting electron-hole separation at the SnO 2 /TiO 2 interface (25)(26)(27)(28)(29). Surface-loaded versions of related assemblies were investigated previously (30).…”