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- ItemMicrotubular Gas Diffusion Electrode Based on Ruthenium-Carbon Nanotubes for Ambient Electrochemical Nitrogen Reduction to Ammonia(Weinheim : Wiley-VCH, 2020) Wei, Xin; Vogel, Dominik; Keller, Laura; Kriescher, Stefanie; Wessling, MatthiasThe drawback of the energy-intensive Haber-Bosch process promotes the research and development of alternative ammonia (NH3) synthesis approaches. The electrochemical nitrogen (N2) reduction reaction (eNRR) may offer a promising method to produce NH3 independent of fossil-fuel-based hydrogen production. However, the low solubility and the low-efficiency mass transport of N2 in aqueous electrolytes are still among the challenges facing the feasibility of eNRR. Herein, we demonstrate a microtubular ruthenium-carbon nanotube gas diffusion electrode (Ru−CNT GDE), for the first time, applying it to electrochemical NH3 synthesis in an H-type cell under ambient conditions. The highest reported Ru-catalyzed NH3 yield rate of 2.1×10−9 mol/cm2 s and high faradaic efficiency of 13.5 % were achieved, showing the superior effect of Ru−CNT GDEs on the eNRR performance. This work provides a new approach for the design and fabrication of self-standing catalyst-loaded GDEs for eNRR. © 2020 The Authors. ChemElectroChem published by Wiley-VCH GmbH
- ItemMulti-walled carbon nanotube-based composite materials as catalyst support for water–gas shift and hydroformylation reactions(London : RSC Publishing, 2019) Wolf, Patrick; Logemann, Morten; Schörner, Markus; Keller, Laura; Haumann, Marco; Wessling, MatthiasIn times of depleting fossil fuel reserves, optimizing industrial catalytic reactions has become increasingly important. One possibility for optimization is the use of homogenous catalysts, which are advantageous over heterogeneous catalysts because of mild reaction conditions as well as higher selectivity and activity. A new emerging technology, supported ionic liquid phase (SILP), was developed to permanently immobilize homogeneous catalyst complexes for continuous processes. However, these SILP catalysts are unable to form freestanding supports by themselves. This study presents a new method to introduce the SILP system into a support made from multi-walled carbon nanotubes (MWCNT). In a first step, SILP catalysts were prepared for hydroformylation as well as low-temperature water–gas shift (WGS) reactions. These catalysts were integrated into freestanding microtubes formed from MWCNTs, with silica (for hydroformylation) or alumina particles (for WGS) incorporated. In hydroformylation, the activity increased significantly by around 400% when the pure MWCNT material was used as SILP support. An opposite trend was observed for WGS, where pure alumina particles exhibited the highest activity. A significant advantage of the MWCNT composite materials is the possibility to coat them with separation layers, which allows their application in membrane reactors for more efficient processes.