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- ItemEffect of pore geometry on ultra-densified hydrogen in microporous carbons(Amsterdam [u.a.] : Elsevier Science, 2021) Tian, Mi; Lennox, Matthew J.; O’Malley, Alexander J.; Porter, Alexander J.; Krüner, Benjamin; Rudić, Svemir; Mays, Timothy J.; Düren, Tina; Presser, Volker; Terry, Lui R.; Rols, Stephane; Fang, Yanan; Dong, Zhili; Rochat, Sebastien; Ting, Valeska P.Our investigations into molecular hydrogen (H2) confined in microporous carbons with different pore geometries at 77 K have provided detailed information on effects of pore shape on densification of confined H2 at pressures up to 15 MPa. We selected three materials: a disordered, phenolic resin-based activated carbon, a graphitic carbon with slit-shaped pores (titanium carbide-derived carbon), and single-walled carbon nanotubes, all with comparable pore sizes of <1 nm. We show via a combination of in situ inelastic neutron scattering studies, high-pressure H2 adsorption measurements, and molecular modelling that both slit-shaped and cylindrical pores with a diameter of ∼0.7 nm lead to significant H2 densification compared to bulk hydrogen under the same conditions, with only subtle differences in hydrogen packing (and hence density) due to geometric constraints. While pore geometry may play some part in influencing the diffusion kinetics and packing arrangement of hydrogen molecules in pores, pore size remains the critical factor determining hydrogen storage capacities. This confirmation of the effects of pore geometry and pore size on the confinement of molecules is essential in understanding and guiding the development and scale-up of porous adsorbents that are tailored for maximising H2 storage capacities, in particular for sustainable energy applications.
- ItemEffect of Alloying Elements in Melt Spun Mg-alloys for Hydrogen Storage(São Carlos : SciELO - Scientific Electronic Library Online, 2016) Rozenberg, Silvia; Saporiti, Fabiana; Lang, Julien; Audebert, Fernando; Botta, Pablo; Stoica, Mihai; Huot, Jacques; Eckert, JürgenIn this paper we report the effect of alloying elements on hydrogen storage properties of melt-spun Mg-based alloys. The base alloys Mg90Si10, Mg90Cu10, Mg65Cu35 (at%) were studied. We also investigated the effect of rare earths (using MM: mischmetal) and Al in Mg65Cu25Al10, Mg65Cu25MM10 and Mg65Cu10Al15MM10 alloys. All the melt-spun alloys without MM show a crystalline structure, and the Mg65Cu25MM10 and Mg65Cu10Al15MM10 alloys showed an amorphous and partially amorphous structure respectively. At 350˚C all the alloys had a crystalline structure during the hydrogen absorption-desorption tests. It was observed that Si and Cu in the binaries alloys hindered completely the activation of the hydrogen absorption. The partial substitution of Cu by MM or Al allowed activation. The combined substitution of Cu by MM and Al showed the best results with the fastest absorption and desorption kinetics, which suggests that this combination can be used for new Mg-alloys to improve hydrogen storage properties.
- ItemFormic Acid Dehydrogenation by a Cyclometalated κ3-CNN Ruthenium Complex(Weinheim : Wiley-VCH, 2020) Léval, Alexander; Junge, Henrik; Beller, MatthiasHydrogen utilization as a sustainable energy vector is of growing interest. We report herein a cyclometalated ruthenium complex [Ru(κ3-CNN)(dppb)Cl], originally described by Baratta, to be active in the selective dehydrogenation (DH) of formic acid (FA) to H2 and CO2. TON's of more than 10000 were achieved under best conditions without observation of CO (detection limit 10 ppm). The distinguished behavior of the catalyst was explored varying the starting conditions. Our observation revealed the complex [Ru(κ3-CNN)(dppb)(OOCH)] as key species in the catalytic cycle. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemEnergy system changes in 1.5 °C, well below 2 °C and 2 °C scenarios(Amsterdam : Elsevier, 2019) Gambhir, Ajay; Rogelj, Joeri; Luderer, Gunnar; Few, Sheridan; Napp, TamarynMeeting the Paris Agreement's goal to limit global warming to well below 2 °C and pursuing efforts towards 1.5 °C is likely to require more rapid and fundamental energy system changes than the previously-agreed 2 °C target. Here we assess over 200 integrated assessment model scenarios which achieve 2 °C and well-below 2 °C targets, drawn from the IPCC's fifth assessment report database combined with a set of 1.5 °C scenarios produced in recent years. We specifically assess differences in a range of near-term indicators describing CO2 emissions reductions pathways, changes in primary energy and final energy across the economy's major sectors, in addition to more detailed metrics around the use of carbon capture and storage (CCS), negative emissions, low-carbon electricity and hydrogen. © 2018 The Authors
- ItemGreen hydrogen from anion exchange membrane water electrolysis: A review of recent developments in critical materials and operating conditions(Cambridge : Royal Society of Chemistry, 2020) Miller, Hamish Andrew; Bouzek, Karel; Hnat, Jaromir; Loos, Stefan; Bernäcker, Christian Immanuel; Weißgärber, Thomas; Röntzsch, Lars; Meier-Haack, JochenHydrogen production using water electrolysers equipped with an anion exchange membrane (AEM), a pure water feed and cheap components such as platinum group metal-free catalysts and stainless steel bipolar plates (BPP) can challenge proton exchange membrane (PEM) electrolysis systems as the state of the art. For this to happen the performance of the AEM electrolyzer must match the compact design, stability, H2purity and high current densities of PEM systems. Current research aims at bringing AEM water electrolysis technology to an advanced level in terms of electrolysis cell performance. Such technological advances must be accompanied by demonstration of the cost advantages of AEM systems. The current state of the art in AEM water electrolysis is defined by sporadic reports in the academic literature mostly dealing with catalyst or membrane development. The development of this technology requires a future roadmap for systematic development and commercialization of AEM systems and components. This will include basic and applied research, technology development & integration, and testing at a laboratory scale of small demonstration units (AEM electrolyzer shortstacks) that can be used to validate the technology (from TRL 2-3 currently to TRL 4-5). This review paper gathers together recent important research in critical materials development (catalysts, membranes and MEAs) and operating conditions (electrolyte composition, cell temperature, performance achievements). The aim of this review is to identify the current level of materials development and where improvements are required in order to demonstrate the feasibility of the technology. Once the challenges of materials development are overcome, AEM water electrolysis can drive the future use of hydrogen as an energy storage vector on a large scale (GW) especially in developing countries. © The Royal Society of Chemistry 2020.