The valorisation of lignin has gained significant interest in bioenergy, which is driven by the abundance of the material coupled with the potential to form value-added compounds. As a result, the range of technologies deployed for this application has increased and more recently includes advanced oxidation processes such as photocatalysis. The complexity of lignin is challenging however, and therefore model compounds, which represent key linkages in the native structure, have become crucial as both a tool for evaluating novel technologies and for providing an insight into the mechanism of conversion. Previously, the β-O-4 dimer, the most abundant linkage found in native lignin, has been extensively used as a model compound. Described herein, however, is the first report of photocatalytic TiO2 technology for the degradation of a β-5 model dimer. Under low power UV-light emitting diode irradiation, complete degradation of the β-5 compound (6.3 × 10−3 mg ml−1 min−1) was achieved along with formation and subsequent removal of reaction intermediates. Investigation into the mechanism revealed within the first 2 min of irradiation there was the formation of a diol species due to consumption of the alkene sidechain. Although the data presented highlights the complexity of the system, which is underpinned by multiple oxidative reaction pathways, an overview of the key photocatalytic processes are discussed including the impact of acetonitrile and role of reactive oxygen species.
published as an Advance Article on the web Atomic absorption spectroscopy of the ionic liquid 1-ethyl-3-methylimidazolium ethanoate ([emim] 2 [O 2 CMe]), prepared according to International Patent WO 96/18459, showed it to contain large amounts of lead impurity: (ca. 0.5 M): [emim] 2 [Pb(O 2 CMe) 4 ] was isolated and shown crystallographically to contain the first known example of a monomeric, homoleptic pentacoordinate lead(II) carboxylate complex, with a stereochemically active lone-pair.
No abstract
High temperature co-electrolysis of steam and carbon dioxide using a solid oxide cell (SOC) has been shown to be an efficient route to produce syngas (CO + H2), which can then be converted to synthetic fuel. Optimization of co-electrolysis requires detailed understanding of the complex reactions, transport processes and degradation mechanisms occurring in the SOC during operation. Currently, electrochemical measurements are conducted in-situ during electrolysis operation, however many analytical techniques are only used ex-situ, before and/or after electrolysis operation. In some cases the analytical techniques used are destructive (e.g. SEM imaging of the cell microstructure). In order to fully understand and characterize co-electrolysis in SOCs, in-situ monitoring of the reactants, products, and the cell itself are necessary. As part of the UK-wide £5.7m 4CU project (A Comprehensive, Coordinated Programme for Carbon Capture and Utilisation Research) we are developing a suite of in-situ characterization techniques for high temperature SOC operation. In this paper we report the use of DRIFTS (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) to probe the reactions occurring during dry CO2 electrolysis and co-electrolysis. The design and commissioning of the rig for in-situ characterization will be presented, along with a discussion on the challenges of spectroscopic access to the areas of interest of an SOC operating at high temperature. Infrared spectra showing CO adsorption on Ni-YSZ powdered catalyst and electrode surfaces will be presented.
Syngas production through co-electrolysis of steam and carbon dioxide has been shown as an effective method of CO2 utilisation, however little is known about the complex surface reaction mechanisms involved. Further understanding is needed in order to optimise SOC operation parameters and inform materials development. Currently many investigative techniques are ex-situ, some of which are even destructive: e.g. SEM imagining of the microstructure. To fully understand reaction intermediates, characterise electrochemical performance, and develop novel materials and microstructures for co-electrolysis SOCs; in-situ analysis methods are required. The EPSRC funded research programme, 4CU aims to enhance the fundamental understanding of CO2 and its role in co-electrolysis by developing a suite of in-situ investigative methods for high temperature SOC operation. Using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) we can monitor both adsorbed and gas phase species in-situ. Variation of potential and temperature conditions allow for visualization of surface mechanisms associated with single atmosphere fuel cell operation. This, along with dual atmosphere measurements, will be discussed. This work illustrates the applicability of the new technique for SOCs operated in a range of atmospheres using Au, Pt and Ag electrodes. The comparison of potential dependent DRIFTS combined with electrochemical measurements provides an important insight into the roles of oxygen ion and proton transport within the systems studied. Figure 1
CO2 emissions are a significant environmental problem which has garnered global interest from both the scientific and political community. One method to reduce emissions is to capture CO2 and convert it to useful products, such as chemical feed-stocks. A method to achieve this is via co-electrolysis of CO2 and H2O, using a high temperature solid oxide cell, to produce synthesis gas – an important intermediate to the production of synthetic liquid fuels. The potential to convert CO2 into synthetic fuel forms a major pathway for global CO2 utilization and could address the issues of depleting fossil fuel reserves and global warming, however, the reaction mechanisms occurring during cell operation for a co-electrolysis system are currently not well understood. This information is necessary to improve performance by engineering materials and operating conditions which are ideal for high gas conversion rates and long term cell performance. Previous studies have suggested that carbonate species may be an important intermediate to CO2 reduction during electrolysis and shows dependencies with temperature and applied potential.[1] This study investigates the electrochemical impedance of electrolysis cells to determine potential rate limiting mechanisms occurring during cell operation. Results correlating cell performance to surface species detected in-situ using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) obtained under varying fuel and temperature conditions will be discussed. [1] D.J. Cumming, C. Tumilson, R. Taylor, S. Chansai, A.V. Call, J. Jacquemin, C. Hardacre, R.H. Elder, Faraday Discuss., 2015, 182, 97-111
Na0.5Bi0.5TiO3 (NBT) is a well-known lead-free piezoelectric material with potential to replace lead zirconate titanate (PZT),1 however high leakage conductivity for the material has been widely reported.2 Through a combination of Impedance Spectroscopy (IS), O2- ion transference (EMF) number experiments and O18 tracer diffusion measurements, combined with Time-of-flight Secondary Ion Mass Spectrometry (TOFSIMS), it was identified that this leakage conductivity was due to oxygen ion conductivity. The volatilization of bismuth during synthesis, causing oxygen vacancies, is believed to be responsible for the leakage conductivity.3 The oxide-ion conductivity, when doped with magnesium, exceeds that of yttria-stabilized zirconia (YSZ) at ~500 °C,3 making it a potential electrolyte material for Intermediate Temperature Solid Oxide Cells (ITSOCs). Figure 1 shows the comparison of bulk oxide ion conductivity between 2 at.% Mg-doped NBT and other known oxide ion conductors. As part of the UK wide £5.7m 4CU project, research has concentrated on trying to develop NBT for use in Intermediate Temperature Solid Oxide Cells (ITSOCS). With the aim of achieving mixed ionic and electronic conduction, transition metals were chemically doped on to the Ti-site. A range of experimental techniques was used to characterize the materials aimed at investigating both conductivity and material structure (Scanning Electron Microscopy (SEM), IS, X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS)). The potential for NBT as an ITSOC material, as well as the challenges of developing the material, will be discussed. (1) Takenaka T. et al. Jpn. J. Appl. Phys 1999, 30, 2236. (2) Hiruma Y. et al. J. Appl. Phys 2009, 105, 084112. (3) Li. M. et al. Nature Materials 2013, 13, 31. Figure 1
No abstract
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.