Core level binding energy for nitrogen doped char: XPS deconvolution analysis from first principles

Amorphous carbon produced from lignocellulosic materials has received much attention in recent years because of its applications in environmental and agricultural management with potential to sequester carbon, serve as a soil amendment, and improve soil aggregation. Modern engineered amorphous carbons with promising properties, such as porous structure, surface functionalities (O, N, P, S) and layers with large number of defects, are used in the field of adsorption and catalysis. There is a growing interest in the production of nitrogen-doped carbonaceous materials because of their excellent properties in a variety of applications such carbon electrodes, heterogenous catalysis adsorption and batteries. However, quantifying the surface nitrogen and oxygen content in amorphous nitrogen doped carbons via deconvolution of C 1s x-ray photoelectron (XPS) spectra remains difficult due to limited information in the literature. No suitable method exists to accurately correlate both the nitrogen and oxygen content to the carbon (C 1s) XPS spectrum in the literature. To improve the interpretation of spectra, the C 1s, N 1s and O 1s core level energy shifts have been calculated for various nitrogenated carbon structures from first principles by performing density functional theory (DFT) based calculations. Furthermore, we propose a new method to improve the self-consistency of the XPS interpretation based on a seven-peak C 1s deconvolution (3 C-C peaks, 3 C-N/-O peaks, and π-π* transition peaks). With the DFT calculations, spectral components arising from surface-defect carbons could be distinguished from aromatic sp2 carbon. The deconvolution method proposed provides C/(N+O) ratios in very good agreement (error less than 5%) with those obtained from total C 1s, N 1s and O 1s peaks. Our deconvolution strategy provides a simple guideline for obtaining high-quality fits to experimental data on the basis of a careful evaluation of experimental conditions and resul

Effect of Surface and Bulk Properties of Mesoporous Carbons on the Electrochemical Behavior of GOx-Nanocomposites

Biofuel cell (BFC) electrodes are typically manufactured by combining enzymes that act as catalysts with conductive carbon nanomaterials in a form of enzyme-nanocomposite. However, a little attention has been paid to effects of the carbon nanomaterials' structural properties on the electrochemical performances of the enzyme-nanocomposites. This work aims at studying the effects of surface and bulk properties of carbon nanomaterials with different degrees of graphitization on the electrochemical performances of glucose oxidase (GOx)-nanocomposites produced by immobilizing GOx within a network of carbon nanopaticles. Two types of carbon nanomaterials were used: graphitized mesoporous carbon (GMC) and purified mesoporous carbon (PMC). Graphitization index, surface functional groups, hydrophobic properties, and rate of aggregation were measured for as-received and acid-treated GMC and PMC samples by using Raman spectrometry, X-ray photoelectron spectroscopy (XPS), contact angle measurement, and dynamic light scattering (DLS), respectively. In addition to these physical property characterizations, the enzyme loading and electrochemical performances of the GOx-nanocomposites were studied via elemental analysis and cyclic voltammetry tests, respectively. We also fabricated BFCs using our GOx-nanocomposite materials as the enzyme anodes, and tested their performances by obtaining current-voltage (IV) plots. Our findings suggest that the electrochemical performance of GOx-nanocomposite material is determined by the combined effects of graphitization index, electrical conductivity and surface chemistry of carbon nanomaterials

Core–Shell Hybrid Nanowires with Protein Enabling Fast Ion Conduction for High‐Performance Composite Polymer Electrolytes

Incorporating nanofillers is one of the promising approaches for simultaneously boosting the ionic conductivity and mechanical properties of solid polymer electrolytes (SPEs). However, effectively creating faster ion‐conduction pathways via nanofillers still remains a big challenge. Herein, core–shell protein–ceramic nanowires for more efficiently building fast ion‐conduction networks in SPEs are reported. The core–shell protein–ceramic nanowires are fabricated via in situ growth of protein coating on the electrospun TiO2 nanowires in a subtly controlled protein‐denaturation process. It is demonstrated that the core–shell protein@TiO2 nanowires effectively facilitate ion‐conduction. As a result, the ionic conductivity, mechanical properties, electrochemical stability, and even Li+ transference number of the SPEs with core–shell protein@TiO2 nanowires are significantly enhanced. The contributions from the 1D morphology of the protein@TiO2 nanowires, and more importantly, the favorable protein structure for further promoting ion‐conduction at the polymer–filler interfaces are analyzed. It is believed that the protein plays a pivotal role in dissociating lithium salts, which benefits from the strong interactions between protein and ions, making the protein serve as a unique “natural channel” for rapidly conducting Li+. This study initiates an effective method of promoting ionic conductivity and constructing faster ion‐conduction networks in SPEs via combining bio‐ and nanotechnology. Advanced core–shell structured protein@TiO2 nanowires enabling fast ion‐conduction in solid polymer electrolytes are reported. The protein@TiO2 nanowires are fabricated via bio‐/nanotechnology, whose protein shell significantly promotes the dissociation of lithium salts and transportation of Li+, due to the unique interactions between protein and ions

Modeling of xylem vessel occlusion in grapevine

Morphological traits of the plant vascular system such as xylem vessel diameter have been implicated in many physiological processes including resistance to drought-induced xylem cavitation and vessel occlusion during infection with vascular wilt disease

A Disposable Multi-Functional Air Filter: Paper Towel/Protein Nanofibers with Gradient Porous Structures for Capturing Pollutants of Broad Species and Sizes

Highly polluted air is usually concentrated with particles of broad sizes and species of gaseous toxic chemicals. Filtration of these pollutants simply relying on size effects is not sufficient; instead, strong interactions between filtering materials and pollutants are in critical need. Moreover, to reduce or even avoid further pollution to the environment from disposing of the massive amount of used air filters demands the development of “green” air filtering materials. Here, we report a high-performance hybrid cellulose/protein air filter with nanofiber structures. Interestingly, it was discovered that textured cellulose paper towel can not only act as a flexible mechanical support but also as a type of air flow regulator that can improve pollutant–nanofilter interactions. Therefore, the high-performance natural protein-based nanofabrics are promoted both mechanically and functionally by textured cellulose paper towel. Study results indicate that this hybrid filtering material possesses excellent removal efficiency for particulate matter with a broad size range, in particular for small pollutants, the most challenging for air filtration, and multiple species of toxic chemicals. This study indicates that the protein/cellulose hybrid system can be used in high-performance air filters and are disposable due to the abundance and environmental friendliness of the original materials

Self-Assembled Protein Nanofilter for Trapping Polysulfides and Promoting Li⁺ Transport in Lithium–Sulfur Batteries

The diffusion of polysulfides in lithium–sulfur (Li–S) batteries represents a critical issue deteriorating the electrochemical performance. Here, borrowing the concepts from air filtration, we design and fabricate a protein-based nanofilter for effectively trapping polysulfides but facilitating Li⁺ transport. The unique porous structures are formed through a protein-directed self-assembly process, and the surfaces are functionalized by the protein residues. The experiments and molecular simulation results demonstrate that our polysulfide nanofilter can effectively trap the dissolved polysulfides and promote Li⁺ transport in Li–S batteries. When the polysulfide nanofilter is added in a Li–S battery, the electrochemical performance of the battery is significantly improved. Moreover, the contribution of the protein nanofilter to the ion transport is further analyzed by correlating filter properties and battery performance. This study is of universal significance for the understanding, design, and fabrication of advanced battery interlayers that can help realize good management of the ion transport inside advanced energy storage devices

Building Ion-Conduction Highways in Polymeric Electrolytes by Manipulating Protein Configuration

Solid polymer electrolytes play a critical role in the development of safe, flexible, and all-solid-state energy storage devices. However, the low ion conductivity has been the primary challenge impeding them from practical applications. Here, we propose a new biotechnology to fabricate novel protein–ceramic hybrid nanofillers for simultaneously boosting the ionic conductivity, mechanical properties, and even adhesion properties of solid polymer electrolytes. This hybrid nanofiller is fabricated by coating ion-conductive soy proteins onto TiO₂ nanoparticles via a controlled denaturation process in appropriate solvents and conditions. It is found that the chain configuration and protein/TiO₂ interactions in the hybrid nanofiller play critical roles in improving not only the mechanical properties but also the ion conductivity, electrochemical stability, and adhesion properties. Particularly, the ion conductivity is improved by one magnitude from 5 × 10^–6 to 6 × 10^–5 S/cm at room temperature. To understand the possible mechanisms, we perform molecular simulation to study the chain configuration and protein/TiO₂ interactions. Simulation results indicate that the denaturation environment and procedures can significantly change the protein configuration and the protein/TiO₂ interactions, both of which are found to be critical for the ion conductivity and mechanical properties of the resultant solid composite electrolytes. This study indicates that biotechnology of manipulating protein configuration can bring novel and promising strategies to build unique ion channels for fast ion conduction in solid polymer electrolytes

iv TABLE OF CONTENTS

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