Energy Materials

A nanocomposite of graphene, cobalt hydroxide and nickel can conveniently be synthesized on gold-silver alloy lines. Using a two-step electrodeposition method, the scaly morphology is pre-deposited on a Ni film, followed by the interconnecting corrugated graphene/cobalt hydroxide composite nanomaterial. Due to the pre-deposited Ni film, the area capacity of the graphene/cobalt hydroxide/Ni electrode is 1.6-times of the graphene/cobalt hydroxide electrode. The kinetic analysis of the graphene/cobalt hydroxide/Ni electrode displays diffusion and non-diffusion contributions of 38% and 62% at 10 mV s−1, respectively. X-ray photoelectron spectroscopy exhibits the oxidation of Co2+ to Co3+ dedicated to the OH- ion insertion. Furthermore, graphene/cobalt hydroxide/Ni//activated carbon flexible micro-supercapacitor (MSC) was assembled by gel KOH-PVA electrolyte, graphene/cobalt hydroxide/Ni (positive electrode), and activated carbon (negative electrode), which manifests maximum volumetric energy of 18.6 mWh cm−3. Moreover, MSC retains over 94% capacitance after 10,000 cycles. After 1,000 continuous bending/unbending cycles at a 180° bending angle with the frequency of 100 mHz, the capacitance retention of MSC is still maintained at 97% of the initial value. The results show outstanding flexibility and mechanical stability of MSC based on graphene/cobalt hydroxide/Ni electrode and confirm that further chemical and physical optimization may lead to the development of quasi-solid-state hybrid MSCs.

Highly water-soluble, persistent, and mobile organic compounds (PMOCs) are more and more often detected in surface and groundwater, evoking potential threats to the environment and human health. Traditional water treatment strategies, including adsorption by activated carbon materials, fail to efficiently remove PMOCs due to their hydrophilic nature. Electro-assisted sorption processes offer a clean, facile, and promising solution to remove PMOCs on activated carbon-based electrodes and potentially allow an easy on-site sorbent regeneration (trap&release). In this work, the electrosorption of five selected PMOCs, that is, tetrapropylammonium (TPA+), benzyltrimethylammonium (BTMA+), p-tosylate (p-TsO-), p-toluenesulfonamide (p-TSA), and methyl-tert-butyl ether (MTBE), were investigated on two comprehensively characterized activated carbon felt (ACF) types carrying different surface functionalities. Significant enrichment factors in ranges of 102 to 103 for charged PMOCs were expected by our first estimation for electro-assisted trap&release on ACFs in flow systems applying potentials in the range of −0.1 V/+0.6 V vs. SHE for ad-/desorption, respectively. Defunctionalized ACF carrying larger density in surface π-systems and lower O-content promises a higher capability in electrosorption processes than the pristine material in terms of better material stability (tested for 5 cycles over 500 h) and better removal efficiency of ionic PMOCs. To improve ACFs adsorption performance for cationic and anionic PMOCs, permanent chemical surface modification and reversible electric polarization as alternative strategies are compared. Our findings explore future electrode and process design of electrosorption for applications to treat water contaminated by emerging PMOCs.

Pneumococcal infections represent a global health threat, which requires novel vaccine developments. Extracellular vesicles are secreted from most cells, including prokaryotes, and harbor virulence factors and antigens. Hence, bacterial membrane vesicles (MVs) may induce a protective immune response. For the first time, we formulate spray-dried gram-positive pneumococcal MVs-loaded vaccine microparticles using lactose/leucine as inert carriers to enhance their stability and delivery for pulmonary immunization. The optimized vaccine microparticles showed a mean particle size of 1–2 µm, corrugated surface, and nanocrystalline nature. Their aerodynamic diameter of 2.34 µm, average percentage emitted dose of 88.8%, and fine powder fraction 79.7%, demonstrated optimal flow properties for deep alveolar delivery using a next-generation impactor. Furthermore, confocal microscopy confirmed the successful encapsulation of pneumococcal MVs within the prepared microparticles. Human macrophage-like THP-1 cells displayed excellent viability, negligible cytotoxicity, and a rapid uptake around 60% of fluorescently labeled MVs after incubation with vaccine microparticles. Moreover, vaccine microparticles increased the release of pro-inflammatory cytokines tumor necrosis factor and interleukin-6 from primary human peripheral blood mononuclear cells. Vaccine microparticles exhibited excellent properties as promising vaccine candidates for pulmonary immunization and are optimal for further animal testing, scale-up and clinical translation.

Abstract Electrochemical ion separation is a promising technology to recover valuable ionic species from water. Pseudocapacitive materials, especially 2D materials, are up-and-coming electrodes for electrochemical ion separation. For implementation, it is essential to understand the interplay of the intrinsic preference of a specific ion (by charge/size), kinetic ion preference (by mobility), and crystal structure changes. Ti3C2Tz MXene is chosen here to investigate its selective behavior toward alkali and alkaline earth cations. Utilizing an online inductively coupled plasma system, it is found that Ti3C2Tz shows a time-dependent selectivity feature. In the early stage of charging (up to about 50 min), K+ is preferred, while ultimately Ca2+ and Mg2+ uptake dominate; this unique phenomenon is related to dehydration energy barriers and the ion exchange effect between divalent and monovalent cations. Given the wide variety of MXenes, this work opens the door to a new avenue where selective ion-separation with MXene can be further engineered and optimized.

The considerable growth of the world population, concomitant with an increase in environmental pollution, aggravates the antinomy between supply and demand for drinking water. Various desalination technologies have been developed to address this issue, allowing for abundant saltwater as a source for drinking water. Electrochemical desalination attracts more and more attention due to its high energy efficiency, facile operation, and low cost. Especially within the last decade, tremendous scientific progress on electrochemical desalination technologies has been made. This paper reviews the development of electrochemical desalination technologies and introduces a facile classification into three generations according to the different working principles. The cell architecture, metrics, advantages, and disadvantages of other electrochemical desalination technologies are introduced and compared.

Capacitive deionization (CDI) is based on ion electrosorption and has emerged as a promising desalination technology, for example, to obtain drinking water from brackish water. As a next-generation technology, battery desalination uses faradaic processes and, thereby, enables higher desalination capacities and remediation of feed water with high molar strength such as seawater. However, the full use of a large capacity of charge transfer processes is limited by the voltage window of water and the need to use electrode materials non-reactive towards the water. Using our multi-channel bi-electrolyte cell, we now introduce for the first time an alloying electrode for sodium removal in the context of water desalination. Separated by a ceramic sodium superionic conductor (NASICON) membrane, the antimony/carbon composite electrode accomplished sodium removal while chlorine removal is enabled via ion electrosorption with nanoporous carbon (activated carbon cloth). In a sodium-ion battery half-cell setup, the antimony/carbon composite electrode reaches an initial capacity of 714 mA h g−1 at a specific current of 200 mA g−1, which shows a slow but continuous degrading over the course of 80 cycles (426 mA h g−1 in 80th cycle). Our hybrid CDI cell provides a desalination capacity of an average of 294 mgNa gSb−1 (748 mgNaCl gSb−1) with a charge efficiency of ca. 74% in a 600 mM NaCl at a specific current of 200 mA g−1 and a voltage range of −2.0 V to +2.0 V.

Due to their various applications, metal oxides are of high interest for fundamental research and commercial usage. Per applications as catalysts or electrochemical devices, the tailored design of metal oxides featuring a high specific surface area and additional functionalities is of the utmost importance for the performance of the resulting materials. We report a new method for preparing free-standing films consisting of hierarchically porous metal oxides (titanium and niobium based) by combining emulsion polymerization and shear-induced monodisperse particle self-assembly in the presence of sol–gel precursors. After thermal treatment, the resulting porous materials can be used as electrodes in Li-ion batteries. The titanium and niobium sol–gel precursors were partially immobilized to the surface of organic core–interlayer particles featuring hydroxyl groups to obtain hybrid organic–inorganic particles through the melt–shear organization process. Free-standing particle-based films, in analogy to elastomeric opal films and colloidal crystals, can be prepared in a convenient one-step preparation process. After thermal treatment, ordered pores are obtained, while the pristine metal oxide precursor shell can be converted to the (mixed) metal oxide matrix. Heat treatment under CO2 leads to mixed-TiNb oxide/carbon hybrid materials. The highly porous derivative structure enhances electrolyte permeation. When tested as Li-ion battery electrodes, it shows a specific capacity of 335 mAh·g–1 at a rate of 10 mA·g–1. After 1000 cycles at 250 mA·g–1, the electrodes still provided a specific capacity of 191 mAh·g–1.

Pillared Ti3C2Tz MXene with a large interlayer spacing (1.75 nm) is shown to be promising for high-power Li-ion batteries. Pillaring dramatically enhances the electrochemical performance, with superior capacities, rate capability, and cycling stability compared to the nonpillared material. In particular, at a high rate of 1 A g–1, the SiO2-pillared MXene has a capacity over 4.2 times that of the nonpillared material. For the first time, we apply in situ electrochemical dilatometry to study the volume changes within the MXenes during (de)lithiation. The pillared MXene has superior performance despite larger volume changes compared to the nonpillared material. These results give key fundamental insights into the behavior of Ti3C2Tz electrodes in organic Li electrolytes and demonstrate that MXene electrodes should be designed to maximize interlayer spacings and that MXenes can tolerate significant initial expansions. After 10 cycles, both MXenes show nearly reversible thickness changes after the charge–discharge process, explaining the stable long-term electrochemical performance.

Extraordinarily homogeneous, freestanding titania-loaded carbon spherogels can be obtained using Ti(acac)2(OiPr)2 in the polystyrene sphere templated resorcinol-formaldehyde gelation. Thereby, a distinct, crystalline titania layer is achieved inside every hollow sphere building unit. These hybrid carbon spherogels allow capitalizing on carbon's electrical conductivity and the lithium-ion intercalation capacity of titania.

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.