Templated dewetting: designing entirely self-organized platforms for photocatalysis

Abstract

Noble metal dewetting on self-organized TiO2 nanotubes – nanoscopic design of photocatalysts towards green H2 generation.

A Dewetted‐Dealloyed Nanoporous Pt Co‐Catalyst Formed on TiO2 Nanotube Arrays Leads to Strongly Enhanced Photocatalytic H2 Production

“…TiO 2 NTs have attracted considerable interest in photocatalysis and photo‐electrochemistry in the last decades due to their reliable and versatile fabrication method, high surface area and one‐dimensional (1D) morphology; namely the latter can provide attractive charge transport properties . Moreover, in the context of the present work, these highly‐ordered TiO 2 nanotube layers can be used as a defined, corrugated photo‐active surface to host the formation of the nanoporous Pt co‐catalyst by a dewetting‐alloying‐dealloying approach …”

“…[39] Moreover, in the context of the present work, these highly-ordered TiO 2 nanotube layers can be used as a defined, corrugated photo-active surface to host the formation of the nanoporous Pt co-catalyst by a dewetting-alloying-dealloying approach. [34,35,40] The TiO 2 NTs were grown by self-organizing electro-chemical anodization of a Ti metal foil in a hot HF/o-H 3 PO 4 electrolyte. [41] The SEM image in Figure 1 a shows the morphology of as-prepared structures.…”

Double‐Side Co‐Catalytic Activation of Anodic TiO2 Nanotube Membranes with Sputter‐Coated Pt for Photocatalytic H2 Generation from Water/Methanol Mixtures

“…However,a s-formed tube membranes are amorphous and in order to form photocatalytically active anatase TiO 2 membranes, the Pt/TiO 2 structures are annealed in air at 500 8Cf or 1h.O wing to the thermal treatment, and as shown in Figure 1c-f and in Figure S1, the Pt depositeda tt he oxide surfacef orms particles andi slands.T his result can be ascribed to solid-state dewetting, that is, the Pt films (when < than ac riticalt hickness) tend to agglomerate into particles and expose the oxide (substrate) surface as ar esult of the minimization of the free surface energy of the metal film, of the oxide and of the metal-oxide interface. [54] Particularly,t he morphology of the substrate (in this case TiO 2 tube top and bottom) and the amount of sputtered metal largely affect the size and distributiono ft he deposited Pt decorations, [55] as showni nF igureS2. Af irst general finding that is well in line with theory on dewetting is that the thicker the metal film, the larger the dewetted particles and the broader their size distribution.…”

“…This result can be ascribed to templated dewetting:t he periodic geometry of the tube bottom provides ad efined pathway for metal film rupture and consequento rdered agglomeration of the Pt film into NPs. [30,54,55] Figure 2shows various cross-sectional SEM images of Pt-decorated NT membranes.T he images are taken at the very top and bottomo ft he tube layers. The penetration depth of the Pt NPsd epends on the structure of the tube substrates.…”

Composition Gradients in Sputtered Ti–Au Alloys: Site-Selective Au Decoration of Anodic TiO2 Nanotubes for Photocatalytic H2 Evolution

“…Thus, the observed photocatalytic improvement seems to be ascribed to an increase of the Au decoration density on the NTs. [18,28] Nevertheless, in an attempt to further increase the Au NP density, we found that the structures grown from homogeneous alloys with a Au content of 2 at.% (H2) show a significantly lower rH2 (2.1 µL h -1 cm -2 ). The reason for this is that these substrates, owing to their relatively high Au content, do not grow ordered NTs but only undefined Au-TiO2 porous structuressee Fig.…”