Abstract
In this study, we intend to synthesize oxynitride hollow porous nanotubes using polymer hollow porous fibers as a template by means of atomic layer deposition (ALD). A continuous hydrogen production system will be developed to convert water into hydrogen and oxygen by visible light.
The unique structure of polymer hollow porous fibers is that they contain internal micro channels that can be integrated into a large-scale nanoreactor based on the oxynitride hollow porous nanotubes for water splitting. Polymer fiber bundles will be used as a template to synthesize oxynitride hollow porous nanotubes by ALD. The oxynitride hollow porous nanotube bundles can absorb visible light more effectively and can be integrated into a large-scale nanoreactor. Through controlling the confined nanospace and length of the nanochannels, surface composition of deposited oxynitride materials, and fluid flow, the efficiency of photochemical reaction will be investigated and optimized. Moreover, in order to deposit highly uniform film on the polymer porous fiber template, a new forced-flow cassette type ALD system will be designed and constructed in this study, based on our experience in developing ALD system in the past few years.
In subproject I, oxynitride with a novel hollow porous nanostructure using polymer hollow porous fibers as a template will be synthesized by the forced-flow cassette type ALD. The oxynitride hollow porous nanotubes will be used as a photocatalyst to fabricate a nanoreactor system for continuous water splitting. The photochemical reaction mechanism will be investigated in-situ by synchrotron facility in subproject II, in which the results will be used to optimize the design of the nanoreactor system. A hydrogen separation system will be designed in subproject II as well. In subproject III, a forced-flow cassette type ALD system will be designed and built for synthesizing oxynitride hollow porous nanotube bundles. The subproject will also select suitable precursors and processing parameters to synthesize oxynitride by the nanolamination process. The polymer hollow porous fiber template, with various porosities and diameters, will be synthesized by subproject IV according to the requirement by subproject I. Computational simulation and mathematical modeling of fluid flow within the nanochannels will also be conducted by subproject IV.
This project has several unique characteristics as follows: (1) the oxynitride catalysts have a unique structure, i.e., hollow porous nanotubes, and can absorb visible light more effectively, (2) the hollow porous nanotube bundles are directly prepared by ALD and can be easily scaled up, (3) a nanoreactor system is designed from the oxynitride hollow porous nanotube bundles for water splitting to generate hydrogen continuously, (4) a forced-flow ALD with a cassette design will be constructed, (5) both computational simulation of fluid flow and in situ study of surface photochemical reaction in nanochannels will be conducted, (6) a hydrogen separation system to separate hydrogen directly from a gaseous water/hydrogen/oxygen mixture will be implemented, and (7) a highly integrated team from NTHU, NCU, ITRC, and ITRI will be formed.

Abstrtact
We propose a three-year project to fabricate Pt and Pt-xM (x=1, 2, 3, M=Ru, Co,Ni) nano- particles on novel porous supports (inverse opal and nano-honeycomb structures) as the catalyst for proton exchange membrane fuel cell (PEMFC) by using plasma enhanced atomic layer deposition (PEALD). It is expected that the Pt and Pt-xM particles deposited by PEALD will be uniform and well-dispersed on such supports. Furthermore, Pt-xM catalysts for PEMFC may exhibit higher performance than pure Pt. The subjects to be studied in the project are as follows:
(1) Fabrication of inverse opal and nano-honeycomb structures and deposition of Pt and different ratios PtRu, PtCo and PtNi alloy nanoparticles on silicon wafer by PEALD. The growth mechanism, surface morphology and basic characteristics will be studied.
(2) Pt and Pt-xM catalysts will be deposited on the novel porous supports and the growth rate will be studied. The Pt-xM catalyst will be heat-treated to obtain homogeneous alloy nanoparticles for better activity.
(3) To grow different size and ratio of Pt-xM and prepare the membrane electrode assembly (MEA) for performance test.
(4) Finally, the application of novel supports combined with Pt-xM catalysts will be evaluated for fuel cell industry
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Abstract
The proposed three-year project will focus on fabrication of modified TiO2 thin film by atomic layer deposition (ALD) or plasma enhanced atomic layer deposition (PEALD) and on their photoelectrochemical and water splitting properties. TiO2 has attracted a great attention in water splitting to generate hydrogen. However, its efficiency is still low because it only absorbs UV light. In order to improve the efficiency, TiO2 can be modified by doping with nitrogen or by deposition of Pt nanoparticles. The challenge to achieve high light efficiency depends on good control of the nitrogen concentration and the loading, size and distribution of Pt nanoparticles. The conventional techniques such as PVD and chemical synthesis method are not suitable for the modification. Therefore, ALD will be employed to uniformly dope nitrogen to and deposit Pt nanoparticles on TiO2 thin film. The topics of this study include the following:
(1) Fabrication of nitrogen-doped TiO2 thin film and Pt nanoparticles on different substrates such as Ti, Si, ITO and FTO by ALD. The optimal fabrication parameters for ALD will be established.
(2) Pt nanoparticles will be deposited on pure and nitrogen-doped TiO2 thin film by ALD. In addition, nitrogen-doped thin film and Pt nanoparticles will also be prepared on different substrates as described above by PEALD.
(3) The photoelectrochemical cell and instrumentation for water splitting will be set up. The photoelectrochemical and water splitting behavior of the films will be tested. It is expected that the efficiency of photoelectrochemical cell will reach 1% and 2000 μmol/gh.
(4) Organic nanowires and carbon nanotubes will be used as a template to prepare one-dimensional nitrogen-doped TiO2 by ALD and PEALD so that the surface area can be substantially increased. Pt nanoparticles will then be deposited on the surface of TiO2, and their photoelectrochemical properties and water splitting behavior will be tested.
(5) Finally, the application of the TiO2 thin film and nanostuctures in hydrogen industry will be evaluated.

Abstract
Proton exchange membrane fuel cell (PEMFC) is an electrochemical device that combines hydrogen and oxygen, with the aid of electrocatalysts, to produce electricity. Structurally, membrane electrode assembly (MEA) is one of the key components in high efficiency PEMFCs. It is generally recognized that MEA consists of gas diffusion layer (GDL), microporous layer, catalysts, and proton exchange membrane. One of the challenges in the commercialization of PEMFCs is the high cost of noble metals used as catalysts (e.g., Pt). An efficient way to decrease the amount of Pt from the catalyst layer has been one of the major concerns. Hence, PEMFCs require anode and cathode catalyst layers that have excellent electrochemical activity. In conventional PEMFC, Pt-based catalyst layer on carbon particles can be prepared by ink-process, i.e., a skillful blending and coating of Pt-supporting carbon particles and Nafion. The carbon and Nafion conduct electrons and protons, respectively. However, the Pt loading in the electrodes usually exceeds 0.5 mg/cm2, and the Pt utilization remains very low (20–30%). Thus, efforts directed at enhancing the performance of Pt-carbon electrodes should concentrate on optimizing carbon configuration with a low Pt loading (or high Pt utilization) and providing an excellent gas/proton accessibility and electronic continuity in gas diffusion electrode (GDE), i.e., deposition of Pt catalysts in GDL.
Accordingly, this project intends to integrate novel design of GDL and advanced Pt deposition into a high efficiency MEA, followed by characterization of Pt catalysts, MEA fabrication and diagnosis analysis. The main work of the project aims at fabrication of two types of carbon nanostructures as GDL: carbon nanofiber (CNF) arrays and carbon sphere (CS) stacking layer. Due to the novel GDL design with unique structure, CNF arrays and CS stacking are expected to replace traditional carbon powders in GDEs prepared by a conventional ink process. The unique GDEs deliver two advantages: (1) ordered gas diffusion path, thus reducing diffusion resistance and (2) faster electronic conductivity, improving the performance of MEAs.
The other key point of the project for enhancing the MEA performance is to apply an atomic layer deposition (ALD) technique for synthesizing active Pt catalysts on GDLs. The ALD technique generates a self-limiting interaction between precursor gases and substrate surface, thus controlling nanoparticle size uniformity. The highest aspect ratio can reach as high as 2000:1, which is suitable for depositing Pt catalysts on the GDLs. The ALD is also used to create different compositions of alloy catalysts such as Pt-Ru alloy with well dispersion and narrow particle size distribution (grain size ≤ 2 nm). Our research group has demonstrated that the Pt-loaded MEA fabricated by ALD has a low Pt loading (~0.016 mg/cm2), which is much lower than commercial MEA (0.5 mg/cm2) and the lowest Pt loading (≈ 0.2 mg/cm2) reported by literature. It is of interest that the Pt catalyst by ALD still exhibits an outstanding electrochemical activity, compared with commercial Pt catalyst.
With the above scope, the target of the first year focuses on synthesis of carbon nanostructures for GDLs. Gas diffusion resistance and hydrophilic/hydrophobic control in the GDLs will be systemically investigated. Key parameters in ALD technique, such as precursor type and operating temperature, will be used to examine their influences on grain growth and physical/chemical characterization. According to the analyses, an optimal parameter setting on control of catalyst size and particle dispersion will be obtained. How the physical/chemical characterization of Pt catalysts affecting the performance of MEA will be also investigated. In the second year, the project aims to directly grow carbon nanospheres on carbon paper or carbon cloth, forming carbon composite GDEs. The other key parameter in ALD, atomic stack layer, is selected as a crucial factor in preparing alloy or bimetallic catalysts. Through adjusting the ratio of gas-in to gas-out number, alloy catalysts with different chemical compositions (so-called nanolaminate) can be successfully obtained. The work of the third year is to investigate the relationship between optimization of ALD, carbon structures, and performance of MEA, based on previous results. Accordingly, the efforts of the project not only provide an advanced technique for preparation of GDL and Pt catalyst with grain size < 2nm, but also shed some lights on commercial possibility for fabrication of MEA based on simplicity and environment-friendly viewpoint.

Abstract
The proposed three-year project will focus on organic nanowire-templated fabrication of titania (TiO2) and zinc oxide (ZnO) nanotubes by atomic layer deposition (ALD) and their photocatalysis properties. There are several methods to fabricate TiO2 and ZnO nanotubes. Among them, template method which can be free of evitable pollutant is the simplest and easiest method, and nanowires can be used as a better template to fabricate nanotubes with a high aspect ratio. The challenge to achieve this goal depends on uniformity of the coating on nanowires. The popular techniques such as CVD, PVD or sol-gel method are not suitable. Therefore, ALD will be employed to uniformly deposit TiO2 or ZnO on the nanowire template. Organic nanowires such as AlQ3, GaQ3, and CuPc will be used as the template because of easy deposition and removal. Different from inorganic nanowires, they can be removed by solvent or low temperature heating. Furthermore, they have many active sites to react with ALD precursors. TiO2 and ZnO have been paid much attention because of their high photocatalytic efficiency. To further improve their photocatalytic efficiency, the materials need to be modified either by doping or by surface deposition with noble metals. Therefore, modified TiO2 and ZnO nanotubes be fabricated by different processes and their photocatalysis performance will also be studied. The topics of this study are as follows:
(1) Fabrication of TiO2, ZnO and mixture of TiO2 and ZnO thin films on different flat substrates. The optimal process for ALD by controlling different parameters will be established.
(2) TiO2 or ZnO will be deposited on organic nanowires by ALD, and their thickness will be controlled by the cycle number. The organic nanowires will be removed by solvent or heating. The photocatalysis behavior of the nanotubes will be tested.
(3) The as-prepared oxide nanotubes will be further modified and their photocatalysis properties will be tested.
(4) Finally, the application of the nanotubes in energy or environment protection will be evaluated.