DC sputter deposited TiO2 layers on FTO: towards a maximum photoelectrochemical response of photoanodes

Abstract

In this work, we examine the photoelectrochemical response of TiO2 layers prepared by reactive DC sputter deposition on conductive glass (FTO). We show that adequate conditioning of the FTO by a very thin (few nm thick) Ti interlayer and optimizing the sputter parameters, compact TiO2 anatase layers can be produced that reach incident photocurrent conversion efficiencies (IPCE) maxima peaking at 75%. This is outperforming many of the best titania photoanode structures (including high surface area 1D and 3D titania structures). The key role of the interlayer is to promote the crystallization of titania in the anatase form during the annealing process (as opposed to rutile in the interlayer-free case). Without this interlayer, an IPCE maxima of ≈43% is obtained for otherwise identically processed electrodes. The present work thus describes a most simple straightforward approach for fabricating compact, high-efficiency TiO2 (anatase) photoanodes. Graphical abstract

Single Atoms in Photocatalysis: Low Loading Is Good Enough!

“…These compact, flat layers provide a simple and defined geometry for illumination and characterization, in terms of loading and distribution of SAs. The layers were produced and characterized as described previously 30 and as briefly given in the Supporting Information. Titania layers were sputtered to a thickness of 200 nm, converted to anatase, and then decorated with Pt SAs (Figure S1).…”

Reactive Deposition Versus Strong Electrostatic Adsorption (SEA): A Key to Highly Active Single Atom Co‐Catalysts in Photocatalytic H2 Generation

“…As mentioned above, as a photocatalytic substrate for our investigations, we use DC sputter deposited anatase layers [ 72 ] that provide a most straightforward morphology and geometry for illumination as well as characterization of loading and SA distribution. For photocatalytic H 2 evolution measurements, we use these layers in a thickness of 200 nm (described and characterized in previous work [ 72 ] and in Figure S1, Supporting Information).…”

“…As mentioned above, as a photocatalytic substrate for our investigations, we use DC sputter deposited anatase layers [ 72 ] that provide a most straightforward morphology and geometry for illumination as well as characterization of loading and SA distribution. For photocatalytic H 2 evolution measurements, we use these layers in a thickness of 200 nm (described and characterized in previous work [ 72 ] and in Figure S1, Supporting Information). For transmission electron microscopy (TEM) investigations, 7 nm thick anatase films were used that were fabricated under the same sputter deposition parameters on photolithographically defined TEM supports as described in the Experimental Section and in previous work.…”

“…TiO 2 Layer Fabrication: TiO 2 layers were formed on FTO and SiO 2 substrates by DC magnetron sputtering (SP-P-US-6M-32 CreaTec Fischer & Co. GmbH), as previously described in literature. [72] First, Ti metal layers were sputtered under a vacuum using a 5″ Ti target (99.995%, HMW Hauner GmbH & Co. KG) at 150 W for 10 s. Next, amorphous TiO 2 layers were sputtered in an Ar:O 2 atmosphere (6.7 × 10 −3 mbar; volume ratio Ar:O 2 = 10:5) using the same Ti target at 500 W for 4 h to reach the thickness of 200 nm. Afterward, the coated substrates were annealed at 450 °C for 1 h in air to crystallize TiO 2 layers.…”

“…These compact, flat layers provide a simple and defined geometry for illumination and characterization, in terms of loading and distribution of SAs. The layers were produced and characterized as described previously [ 72 ] and as briefly given in the Experimental Section.…”