Synthesis of a Versatile Building Block for the Preparation of 6-N-Derivatized α-Galactosyl Ceramides: Rapid Access to Biologically Active Glycolipids

A concise route to the 6-azido-6-deoxy-α-galactosyl-phytosphingosine derivative 9 is reported. Orthogonal protection of the two amino groups allows elaboration of 9 into a range of 6-N-derivatized α-galactosyl ceramides by late-stage introduction of the acyl chain of the ceramide and the 6-N-group in the sugar head-group. Biologically active glycolipids 6 and 8 have been synthesized to illustrate the applicability of the approach

Is lithium the key for nitrogen electroreduction?

The Haber-Bosch process converts nitrogen (N2) and hydrogen (H2) into ammonia (NH3) over iron-based catalysts. Today, 50% of global agriculture uses Haber-Bosch NH3 in fertilizer. Efficient synthesis requires enormous energy to achieve extreme temperatures and pressures, and the H2 is primarily derived from methane steam reforming. Hence, the Haber-Bosch process accounts for at least 1% of global greenhouse gas emissions (1). Electrochemical N2 reduction to make NH3, powered by renewable electricity under ambient conditions, could provide a localized and greener alternative. On page 1187 of this issue, Suryanto et al. (2) report highly efficient and stable electrochemical N2 reduction based on a recyclable proton donor. This study builds on earlier work showing that an electrolyte containing a lithium salt in an organic solvent with a sacrificial proton donor was unmatched in its ability to unequivocally reduce N2 (3, 4). In both studies, it is still unclear why lithium is so critical

Machine learning as an online diagnostic tool for proton exchange membrane fuel cells

Proton exchange membrane fuel cells are considered a promising power supply system with high efficiency and zero emissions. They typically work within a relatively narrow range of temperature and humidity to achieve optimal performance; however, this makes the system difficult to control, leading to faults and accelerated degradation. Two main approaches can be used for diagnosis, limited data input which provides an unintrusive, rapid but limited analysis, or advanced characterisation that provides a more accurate diagnosis but often requires invasive or slow measurements. To provide an accurate diagnosis with rapid data acquisition, machine learning methods have shown great potential. However, there is a broad approach to the diagnostic algorithms and signals used in the field. This article provides a critical view of the current approaches and suggests recommendations for future methodologies of machine learning in fuel cell diagnostic applications

Investigating the effect of thermal gradients on stress in solid oxide fuel cell anodes using combined synchrotron radiation and thermal imaging

Thermal gradients can arise within solid oxide fuel cells (SOFCs) due to start-up and shut-down, non-uniform gas distribution, fast cycling and operation under internal reforming conditions. Here, the effects of operationally relevant thermal gradients on Ni/YSZ SOFC anode half cells are investigated using combined synchrotron X-ray diffraction and thermal imaging. The combination of these techniques has identified significant deviation from linear thermal expansion behaviour in a sample exposed to a one dimensional thermal gradient. Stress gradients are identified along isothermal regions due to the presence of a proximate thermal gradient, with tensile stress deviations of up to 75Â MPa being observed across the sample at a constant temperature. Significant strain is also observed due to the presence of thermal gradients when compared to work carried out at isothermal conditions

Developments in Dilatometry for Characterisation of Electrochemical Devices

Since the 1970s, electrochemical dilatometry (ECD) has been used to investigate the dilation of layered host materials due to the intercalation of guest ions, atoms or molecules, and has recently gained traction in application to various electrochemical devices, such as lithium-ion batteries (LiBs), which have electrodes that undergo volume changes during cycling, resulting in particle cracking and electrode degradation. With resolution capabilities spanning tens of microns down to a few nanometres, dilatometry is a valuable tool in understanding how commonly used electrodes dilate and degrade and can therefore be of critical value in improving their performance. In recent years, there has been a plethora of studies using dilatometry as a monitoring tool for understanding operating performance in various electrochemical devices; however, to our knowledge, there has been no in-depth review of this body of research to date. This paper seeks to address this by reviewing how dilatometry works and how it has been used for the characterisation of electrochemical energy storage devices

Efficient harvesting and storage of solar energy of an all-vanadium solar redox flow battery with a MoS2@TiO2 photoelectrode

Solar redox flow batteries constitute an emerging technology that provides a smart alternative for the capture and storage of discontinuous solar energy through the photo-generation of the discharged redox species employed in traditional redox flow batteries. Here, we show that a MoS2-decorated TiO2 (MoS2@TiO2) photoelectrode can successfully harvest light to be stored in a solar redox flow battery using vanadium ions as redox active species in both the catholyte and anolyte, and without the use of any bias. The MoS2@TiO2 photoelectrode achieved an average photocurrent density of ∼0.4 mA cm−2versus 0.08 mA cm−2 for bare TiO2, when tested for the oxidation of V4+ to V5+, attributed to a more efficient light harvesting and charge separation for the MoS2@TiO2 relative to TiO2. The designed solar redox flow cell exhibited an optimal overall solar-to-output energy conversion efficiency (SOEE) of ∼4.78%, which outperforms previously reported solar redox flow batteries. This work demonstrates the potential of the MoS2@TiO2 photoelectrode to efficiently convert solar energy into chemical energy in a solar redox flow battery, and it also validates the great potential of this technology to increase reliability in renewable energies

Using In-Situ Laboratory and Synchrotron-Based X-ray Diffraction for Lithium-Ion Batteries Characterization: A Review on Recent Developments

Renewable technologies, and in particular the electric vehicle revolution, have generated tremendous pressure for the improvement of lithium ion battery performance. To meet the increasingly high market demand, challenges include improving the energy density, extending cycle life and enhancing safety. In order to address these issues, a deep understanding of both the physical and chemical changes of battery materials under working conditions is crucial for linking degradation processes to their origins in material properties and their electrochemical signatures. In situ and operando synchrotron-based X-ray techniques provide powerful tools for battery materials research, allowing a deep understanding of structural evolution, redox processes and transport properties during cycling. In this review, in situ synchrotron-based X-ray diffraction methods are discussed in detail with an emphasis on recent advancements in improving the spatial and temporal resolution. The experimental approaches reviewed here include cell designs and materials, as well as beamline experimental setup details. Finally, future challenges and opportunities for battery technologies are discussed

High-power nitrided TiO2 carbon felt as the negative electrode for all-vanadium redox flow batteries

This work describes the design of an electrode with enhanced performance applied to all-vanadium redox flow batteries (VRFBs). This new electrode consists of a structural porous carbon felt decorated with TiO2 rutile nanoparticles, which has been nitrided using ammonolysis at 900 °C. An outstanding charge and mass transfer over the electrode-electrolyte interface was observed as a consequence of the synergetic effect of N- and O-functionalization over carbon felt (CF) and the partial formation of TiN (metallic conductor) phase. Moreover, this material has not only improved in terms of catalysis towards the V3+/V2+ redox reaction (k0 = 1.6 × 10−3 cm s−1), but also inhibited the hydrogen evolution reaction (HER), which is one of the main causes of imbalances that lead to battery failure. This led to an impressive high-power peak output value up to 700 mW cm−2, as well as work at high current density in galvanostatic conditions (i.e. 150 mA cm−2), exhibiting low ohmic losses (overpotential) and great redox single cell reversibility, with a superior energy efficiency of 71%. An inexpensive, earth abundant and scalable synthesis method to boost VRFBs technology based on nitrided CF@TiO2 is presented, being able to overcome certain constrains, and therefore to achieve high energy and power densities