Uniform ALD deposition of Pt nanoparticles within 1D anodic TiO2 nanotubes for photocatalytic H2 generation

Abstract

In the present work we investigate the utilization of Pt nanoparticles produced by atomic layer deposition (ALD) within anodic TiO 2 nanotube (NT) layers for photocatalytic H 2 production. By varying numbers of ALD cycles, Pt nanoparticles with different diameters, uniformly decorating the tube walls were produced. The Pt nanoparticle size (2-15 nm), the Pt mass loading and areal density were strongly dependent on the number of Pt ALD cycles. The deposited Pt nanoparticles turned out to be highly effective as co-catalyst for photocatalytic H 2 generation. A most effective performance for solar light photocatalysis was reached after 26 ALD cycles (yielding an optimal areal coverage with particles of a diameter ≈ 7 nm). For UV light optimum photocatalytic efficiency was reached after 40 ALD cycles.

Spaced TiO2 Nanotubes Enable Optimized Pt Atomic Layer Deposition for Efficient Photocatalytic H2 Generation

“…In addition, these results confirm that sub‐nanometer nanoparticles in TiO 2 NTs can be deposited deep in a 3D structure in a homogenous manner by using ALD. It is important to note that, for CP tubes, an onset of deposition is observed only after ≥20 cycles for 7 μm CP NTs, demonstrating a strong difference to SP NTs, for which ALD creates Pt deposition already after only two deposition cycles. This finding is ascribed to the enhanced diffusion of ALD precursors toward SP tube walls in comparison with CP NTs.…”

“…Likewise, under solar illumination, the highest activity towards H 2 generation is measured after ten ALD cycles (10.53 μL h −1 ) followed by that for two cycles (9.41 μL h −1 ). The large difference between the evolved H 2 under UV and solar light is attributed to the different light absorption characteristics of Pt‐decorated TiO 2 NT layers at different wavelengths …”

“…The large difference between the evolved H 2 under UV and solar light is attributed to the different light absorptionc haracteristics of Pt-decorated TiO 2 NT layersa td ifferent wavelengths. [25] When the number of ALD cycles is increased to 20 or 72, the nanostructured electrodes exhibit al ower activity towardsH 2 generation,t hat is, 20 ALD cycles leads to 83 mLh À1 and 72 cycles yields 20 mLh À1 under UV light.U nder solari llumination, SP NTsatahigher number of ALD cycles display poor photocatalytic hydrogen generation rate, for instance, 1.29 mLh À1 after 20 cycles and 0.16 mLh À1 after 72 cycles.Clearly,the photocatalytic H 2 generation rate enhances initially with increasing Pt content,r eaches am aximum, and then declines once the Pt content is beyonda no ptimized amount.T he reduction in the photocatalytic activity is attributed to 1) an oxide shading effect by Pt, that is, al arge amount of Pt depositions hades the photosensitive TiO 2 surfaceo rh inders the light absorption, thus decreasing the surface concentration of electrons and holes available for reaction; [32] 2) larger Pt particles or higher metal loadings may providem ore recombination sites for photogenerated electrons and holes. [33] Furthermore, we evaluated CP NTsd eposited with Pt by using as imilara pproach.…”

Hierarchical 3D TiO2 Nanotube Arrays Sensitized by Graphene Oxide and ZnxCdyS for High Performance Photoelectrochemical Applications

“…Photocatalysis is central to many industrial applications such as massive production of hydrogen by water photolysis, renewable energy from solar cells, photocatalytic antibacterial devices, removal of volatile organic compounds (VOCs) from gas or liquid media, purification of wastewater, electricity by fuel cells, photo‐induced anti‐fogging applications and others . Among many candidates for photocatalysis, titanium dioxide (TiO 2 ) is almost the only material suitable for industrial use because of its most efficient photoactivity, the highest stability, the best environmental friendliness, and the lowest cost .…”

A Brief Review on Synthesis of Metal Oxide Based Nanocompositesandtheir Photocatalytic Applications

“…Among the photocatalyst (TiO 2 ) have got wide attention because of its valence band edge positions and conduction band too. This is suitable for a stable and nontoxic property because of its orthogonal electron-hole separation and directional charge transport[23]. The different cocatalyst is also used for…”