NMR proton relaxation for measuring the relative concentration of nanoparticles in liquids.

The measurement of relative concentration of nanoparticles in liquids has been investigated using NMR proton relaxation, addressing a gap in analytical capabilities for highly concentrated dispersions. This technique has a limited footprint, short measurement time and ease of operation making it a promising quality control method to support the development and manufacture of nanomaterials.

How to Tailor Porous Boron Nitride Properties for Applications in Interfacial Processes.

The research of new porous materials for applications in interfacial processes is key to addressing global energy and sustainability challenges. For example, porous materials can be used to store fuels such as hydrogen or methane or to separate chemical mixtures reducing the energy currently required by thermal separation processes. Their catalytic properties can be exploited to convert adsorbed molecules into valuable or less hazardous chemicals, thereby reducing energy consumption or pollutants emissions. Porous boron nitride (BN) has appeared as a promising material for applications in molecular separations, gas storage, and catalysis owing to its high surface area and thermal stability, as well as its tunable physical properties and chemistry. However, the production of porous BN is still limited to the laboratory scale, and its formation mechanism, as well as ways to control porosity and chemistry, are yet to be fully understood. In addition, studies have pointed toward the instability of porous BN materials when exposed to humidity, which could significantly impact performance in industrial applications. Studies on porous BN performance and recyclability when employed in adsorption, gas storage, and catalysis remain limited, despite encouraging preliminary studies. Moreover, porous BN powder must be shaped into macrostructures (e.g., pellets) to be used commercially. However, common methods to shape porous materials into macrostructures often cause a reduction in the surface area and/or mechanical strength. In recent years, research groups, including ours, have started addressing the challenges discussed above. Herein, we summarize our collective findings through a selection of key studies. First, we discuss the chemistry and structure of BN, clarifying confusion around terminology and discussing the hydrolytic instability of the material in relation to its structure and chemistry. We demonstrate a way to reduce the instability in water while still maintaining high specific surface area. We propose a mechanism for the formation of porous BN and discuss the effects of different synthesis parameters on the structure and chemistry of porous BN, therefore providing a way to tune its properties for selected applications. While the syntheses covered often lead to a powder product, we also present ways to shape porous BN powders into macrostructures while still maintaining high accessible surface area for interfacial processes. Finally, we evaluate porous BN performance for chemical separations, gas storage, and catalysis. While the above highlights key advances in the field, further work is needed to allow deployment of porous BN. Specifically, we suggest evaluating its hydrolytic stability, refining the ways to shape the material into stable and reproducible macrostructures, establishing clear design rules to produce BN with specific chemistry and porosity, and, finally, providing standardized test procedures to evaluate porous BN catalytic and sorptive properties to facilitate comparison.

Surface Analysis of Pristine and Cycled NMC/Graphite Lithium-Ion Battery Electrodes: Addressing the Measurement Challenges.

Lithium-ion batteries are the most ubiquitous energy storage devices in our everyday lives. However, their energy storage capacity fades over time due to chemical and structural changes in their components, via different degradation mechanisms. Understanding and mitigating these degradation mechanisms is key to reducing capacity fade, thereby enabling improvement in the performance and lifetime of Li-ion batteries, supporting the energy transition to renewables and electrification. In this endeavor, surface analysis techniques are commonly employed to characterize the chemistry and structure at reactive interfaces, where most changes are observed as batteries age. However, battery electrodes are complex systems containing unstable compounds, with large heterogeneities in material properties. Moreover, different degradation mechanisms can affect multiple material properties and occur simultaneously, meaning that a range of complementary techniques must be utilized to obtain a complete picture of electrode degradation. The combination of these issues and the lack of standard measurement protocols and guidelines for data interpretation can lead to a lack of trust in data. Herein, we discuss measurement challenges that affect several key surface analysis techniques being used for Li-ion battery degradation studies: focused ion beam scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and time-of-flight secondary ion mass spectrometry. We provide recommendations for each technique to improve reproducibility and reduce uncertainty in the analysis of NMC/graphite Li-ion battery electrodes. We also highlight some key measurement issues that should be addressed in future investigations.

Atom-efficient synthesis of a benchmark electrolyte for magnesium battery applications.

The benchmark magnesium electrolyte, [Mg2Cl3]+ [AlPh4]-, can be prepared in a 100% atom-economic fashion by a ligand exchange reaction between AlCl3 and two molar equivalents of MgPh2. NMR and vibrational spectroscopy indicate that the reported approach results in a simpler ionic composition than the more widely adopted synthesis route of combining PhMgCl with AlCl3. Electrochemical performance has been validated by polarisation tests and cyclic voltammetry, which demonstrate excellent stability of electrolytes produced via this atom-efficient approach.

Rapid monitoring of graphene exfoliation using NMR proton relaxation.

Graphene is now being produced on an industrial scale and there is a pressing need for rapid in-line measurements of particle size for Quality Assurance and Quality Control (QA/QC). Standardised characterisation techniques such as electron microscopy and scanning probe microscopy can be time consuming and may require pre-processing steps and/or solvent elimination prior to measurements. Herein, we demonstrate the use of nuclear magnetic resonance (NMR) proton relaxation as a powerful method for monitoring the sonication assisted liquid phase exfoliation of graphene. This technique requires little or no sample preparation and the resulting spin-spin relaxation time showed a strong correlation with particle size, exfoliation yield and specific surface area measurements. As the NMR proton relaxation method is rapid, inexpensive, and can potentially be operated in-line, it shows great promise to become a valuable QA/QC method for graphene production methods in liquid.

Using nuclear magnetic resonance proton relaxation to probe the surface chemistry of carbon 2D materials.

Nanomaterials exhibit a high surface-area-to-mass ratio, making surface properties key to optimising product performance. However, characterising surfaces at the nanoscale is difficult to achieve, especially as nanomaterials are often in liquid dispersions. Herein, we demonstrate the use of nuclear magnetic resonance proton relaxation for rapid characterisation of the surface chemistry of graphitic materials.

Nanoscale characterization of plasma functionalized graphitic flakes using tip-enhanced Raman spectroscopy.

The chemical functionalization of graphene nanomaterials allows for the enhancement of their properties for novel functional applications. However, a better understanding of the functionalization process by determining the amount and location of functional groups within individual graphene nanoplatelets remains challenging. In this work, we demonstrate the capability of tip-enhanced Raman spectroscopy (TERS) to investigate the degree and spatial variability of the appearance of disorder in graphitic nanomaterials on the nanoscale with three different levels of nitrogen functionalization. TERS results are in excellent agreement with those of confocal Raman spectroscopy and chemical analysis, determined using x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry, of the functionalized materials. This work paves the way for a better understanding of the functionalization of graphene and graphitic nanomaterials at the nano-scale, micro-scale, and macro-scale and the relationship between the techniques and how they relate to the changes in material properties of industrial importance.

Porous Boron Nitride Materials: Influence of Structure, Chemistry and Stability on the Adsorption of Organics.

Porous boron nitride (BN) is structurally analogous to activated carbon. This material is gaining increasing attention for its potential in a range of adsorption and chemical separation applications, with a number of recent proof-of-concept studies on the removal of organics from water. Today though, the properties of porous BN-i.e., surface area, pore network, chemistry-that dictate adsorption of specific organics remain vastly unknown. Yet, they will need to be optimized to realize the full potential of the material in the envisioned applications. Here, a selection of porous BN materials with varied pore structures and chemistries were studied for the adsorption of different organic molecules, either directly, through vapor sorption analyses or as part of a water/organic mixture in the liquid phase. These separations are relevant to the industrial and environmental sectors and are envisioned to take advantage of the hydrophobic character of the BN sheets. The materials were tested and regenerated and their physical and chemical features were characterized before and after testing. This study allowed identifying the adsorption mechanisms, assessing the performance of porous BN compared to benchmarks in the field and outlining ways to improve the adsorption performance further.

Template-Free Synthesis of Highly Porous Boron Nitride: Insights into Pore Network Design and Impact on Gas Sorption.

Production of biocompatible and stable porous materials, e.g., boron nitride, exhibiting tunable and enhanced porosity is a prerequisite if they are to be employed to address challenges such as drug delivery, molecular separations, or catalysis. However, there is currently very limited understanding of the formation mechanisms of porous boron nitride and the parameters controlling its porosity, which ultimately prevents exploiting the material's full potential. Herein, we produce boron nitride with high and tunable surface area and micro/mesoporosity via a facile template-free method using multiple readily available N-containing precursors with different thermal decomposition patterns. The gases are gradually released, creating hierarchical pores, high surface areas (>1900 m2/g), and micropore volumes. We use 3D tomography techniques to reconstruct the pore structure, allowing direct visualization of the mesopore network. Additional imaging and analytical tools are employed to characterize the materials from the micro- down to the nanoscale. The CO2 uptake of the materials rivals or surpasses those of commercial benchmarks or other boron nitride materials reported to date (up to 4 times higher), even after pelletizing. Overall, the approach provides a scalable route to porous boron nitride production as well as fundamental insights into the material's formation, which can be used to design a variety of boron nitride structures.