| 1. |
- Kaindl, Reinhard, et al.
(author)
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Aerosol Jet Printing of Graphene and Carbon Nanotube Patterns on Realistically Rugged Substrates
- 2021
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In: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 6:50, s. 34301-34313
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Journal article (peer-reviewed)abstract
- Direct-write additive manufacturing of graphene and carbon nanotube (CNT) patterns by aerosol jet printing (AJP) is promising for the creation of thermal and electrical interconnects in (opto)electronics. In realistic application scenarios, this however often requires deposition of graphene and CNT patterns on rugged substrates such as, for example, roughly machined and surface oxidized metal block heat sinks. Most AJP of graphene/CNT patterns has thus far however concentrated on flat wafer-or foil type substrates. Here, we demonstrate AJP of graphene and single walled CNT (SWCNT) patterns on realistically rugged plasma electrolytic-oxidized (PEO) Al blocks, which are promising heat sink materials. We show that AJP on the rugged substrates offers line resolution of down to similar to 40 mu m width for single AJP passes, however, at the cost of noncomplete substrate coverage including noncovered mu m-sized pores in the PEO Al blocks. With multiple AJP passes, full coverage including coverage of the pores is, however, readily achieved. Comparing archetypical aqueous and organic graphene and SWCNT inks, we show that the choice of the ink system drastically influences the nanocarbon AJP parameter window, deposit microstructure including crystalline quality, compactness of deposit, and inter/intrapass layer adhesion for multiple passes. Simple electrical characterization indicates aqueous graphene inks as the most promising choice for AJP-deposited electrical interconnect applications. Our parameter space screening thereby forms a framework for rational process development for graphene and SWCNT AJP on application-relevant, rugged substrates.
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| 2. |
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| 3. |
- Schubert, Jasmin S., et al.
(author)
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Elucidating the formation and active state of Cu co-catalysts for photocatalytic hydrogen evolution
- 2021
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In: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 9:38, s. 21958-21971
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Journal article (peer-reviewed)abstract
- The design of active and selective co-catalysts constitutes one of the major challenges in developing heterogeneous photocatalysts for energy conversion applications. This work provides a comprehensive insight into thermally induced bottom-up generation and transformation of a series of promising Cu-based co-catalysts. We demonstrate that the volcano-type HER profile as a function of calcination temperature is independent of the type of the Cu precursor but is affected by changes in oxidation state and location of the copper species. Supported by DFT modeling, our data suggest that low temperature (<200 degrees C) treatments facilitate electronic communication between the Cu species and TiO2, which allows for a more efficient charge utilization and maximum HER rates. In contrast, higher temperatures (>200 degrees C) do not affect the Cu oxidation state, but induce a gradual, temperature-dependent surface-to-bulk diffusion of Cu, which results in interstitial, tetra-coordinated Cu+ species. The disappearance of Cu from the surface and the introduction of new defect states is associated with a drop in HER performance. This work examines electronic and structural effects that are in control of the photocatalytic activity and can be transferred to other systems for further advancing photocatalysis.
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| 4. |
- Schubert, Jasmin S., et al.
(author)
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Nature of the Active Ni State for Photocatalytic Hydrogen Generation
- 2023
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In: Advanced Materials Interfaces. - : WILEY. - 2196-7350.
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Journal article (peer-reviewed)abstract
- Thermal treatments can have detrimental effects on the photocatalytic hydrogen (H2) evolution performance and impact the formation mechanism of the active state of surface-supported co-catalysts. In this work, a range of Ni-based co-catalysts is investigated immobilized on TiO2, evaluated their H2 evolution rates in situ over 21 h, and analyzed the samples at various stages with a comprehensive set of spectroscopic and microscopy techniques. It is found that achieving the optimal hydrogen evolution (HER) performance requires the right Ni0:Ni2+ ratio, rather than only Ni0, and that Ni needs to be weakly adsorbed on the TiO2 surface to create a dynamic state. Under these conditions, Ni can undergo an efficient redox shuttle, involving the transformation of Ni2+ to Ni0 and back after releasing the accumulated electrons for H+ reduction (i.e., Ni2+ <-> Ni0). Yet, when the calcination temperature of the Ni/TiO2 photocatalysts increases, resulting in stronger coordination/adsorption of Ni on TiO2, this process is gradually inhibited, which ultimately leads to decreased HER performances. This work emphasizes the significance and influence of thermal treatments on the Ni active state formation - a process that can be relevant to other HER co-catalysts. This research underscores the impact of thermal treatment on the formation of Nis active state for hydrogen evolution reaction (HER) . For optimal performance, Ni should weakly adsorb onto the substrate, efficiently shuttling between Ni2+ and Ni0 and reversing after H+ reduction (Ni2+ <-> Ni0). However, raising the calcination temperature strengthens Ni coordination/adsorption on the substrate, gradually inhibiting this process and reducing HER performances.image
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| 5. |
- Wichmann, H-Erich, et al.
(author)
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Comprehensive catalog of European biobanks
- 2011
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In: Nature Biotechnology. - : Springer Science and Business Media LLC. - 1087-0156 .- 1546-1696. ; 29:9, s. 795-797
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Journal article (peer-reviewed)
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