3 research outputs found
Isotope Labelling for Reaction Mechanism Analysis in DBD Plasma Processes
Dielectric barrier discharge (DBD) plasmas and plasma catalysis are becoming an alternative procedure to activate various gas phase reactions. A low-temperature and normal operating pressure are the main advantages of these processes, but a limited energy efficiency and little selectivity control hinder their practical implementation. In this work, we propose the use of isotope labelling to retrieve information about the intermediate reactions that may intervene during the DBD processes contributing to a decrease in their energy efficiency. The results are shown for the wet reforming reaction of methane, using D2O instead of H2O as reactant, and for the ammonia synthesis, using NH3/D2/N2 mixtures. In the two cases, it was found that a significant amount of outlet gas molecules, either reactants or products, have deuterium in their structure (e.g., HD for hydrogen, CDxHy for methane, or NDxHy for ammonia). From the analysis of the evolution of the labelled molecules as a function of power, useful information has been obtained about the exchange events of H by D atoms (or vice versa) between the plasma intermediate species. An evaluation of the number of these events revealed a significant progression with the plasma power, a tendency that is recognized to be detrimental for the energy efficiency of reactant to product transformation. The labelling technique is proposed as a useful approach for the analysis of plasma reaction mechanisms
Supported Porous Nanostructures Developed by Plasma Processing of Metal Phthalocyanines and Porphyrins
The large area scalable fabrication of supported porous metal and metal oxide
nanomaterials is acknowledged as one of the greatest challenges for their eventual
implementation in on-device applications. In this work, we will present a comprehensive
revision and the latest results regarding the pioneering use of commercially available
metal phthalocyanines and porphyrins as solid precursors for the plasma-assisted
deposition of porous metal and metal oxide films and three-dimensional nanostructures
(hierarchical nanowires and nanotubes). The most advanced features of this method
relay on its ample general character from the point of view of the porous material
composition and microstructure, mild deposition and processing temperature and energy
constrictions and, finally, its straightforward compatibility with the direct deposition of the
porous nanomaterials on processable substrates and device-architectures. Thus, taking
advantage of the variety in the composition of commercially available metal porphyrins
and phthalocyanines, we present the development of metal and metal oxides layers
including Pt, CuO, Fe2O3, TiO2, and ZnO with morphologies ranging from nanoparticles
to nanocolumnar films. In addition, we combine this method with the fabrication by
low-pressure vapor transport of single-crystalline organic nanowires for the formation of
hierarchical hybrid organic@metal/metal-oxide and @metal/metal-oxide nanotubes. We
carry out a thorough characterization of the films and nanowires using SEM, TEM, FIB
3D, and electron tomography. The latest two techniques are revealed as critical for the
elucidation of the inner porosity of the layers.Ministerio de Ciencia, InnovaciĂłn y Universidades MAT2016-79866-R, PID2019- 110430GB-C21ConsejerĂa de EconomĂa y Conocimiento, Junta de AndalucĂa P18- RT-348
Enhanced stability of perovskite solar cells incorporating dopant-free Crystalline spiro-OMeTAD layers by vacuum sublimation
The main handicap still hindering the eventual exploitation of organometal halide perovskite-based solar cells is their poor stability under prolonged illumination, ambient conditions, and increased temperatures. This article shows for the first time the vacuum processing of the most widely used solid-state hole conductor (SSHC), i.e., the Spiro-OMeTAD [2,2âČ,7,7âČ-tetrakis (N,N-di-p-methoxyphenyl-amine) 9,9âČ-spirobifluorene], and how its dopant-free crystalline formation unprecedently improves perovskite solar cell (PSC) stability under continuous illumination by about two orders of magnitude with respect to the solution-processed reference and after annealing in air up to 200 °C. It is demonstrated that the control over the temperature of the samples during the vacuum deposition enhances the crystallinity of the SSHC, obtaining a preferential orientation along the ÏâÏ stacking direction. These results may represent a milestone toward the full vacuum processing of hybrid organic halide PSCs as well as light-emitting diodes, with promising impacts on the development of durable devices. The microstructure, purity, and crystallinity of the vacuum sublimated Spiro-OMeTAD layers are fully elucidated by applying an unparalleled set of complementary characterization techniques, including scanning electron microscopy, X-ray diffraction, grazing-incidence small-angle X-ray scattering and grazing-incidence wide-angle X-ray scattering, X-ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy.The authors thank the âAgencia Estatal de InvestigaciĂłnâ, âConsejerĂa de EconomĂa y Conocimiento de la Junta de AndalucĂaâ (USâ1263142), âMinisterio de EconomĂa y Competitividadâ (MAT2016â79866âR, MAT2013â42900âP, FPA2016â77689âC2â1âR, and MAT2016â76892âC3â2âR) and the European Union (EU) through cohesion fund and FEDER 2014â2020 programs for financial support. J.R.S.âV. and A.B. acknowledge the EU project PlasmaPerovSol and funding from the European Union's Horizon 2020 research and innovation programme under the Marie SkĆodowskaâCurie grant agreement ID 661480. J.R.S.âVâ and M.C.L.âS. thank the University of Seville through the VI âPlan Propio de InvestigaciĂłn y Transferencia de la USâ (VI PPITâUS). This research has received funding from the EUâH2020 research and innovation programme under Grant Agreement No. 654360 having benefitted from the access provided by Technische UniversitĂ€t Graz at ElettraâTUG in Trieste (IT) within the framework on the NFFA (Nanoscience Foundries & Fine Analysis) Europe Transnational Access Activity. F.J.A. and J.R.S.âV. acknowledge the âJuan de la Ciervaâ and âRamon y Cajalâ national programs, respectively