Carbon Surface Research Articles

Synergistic catalysis in Pd/La-CeO2 enhanced CH4 oxidation: The role of water and reactive oxygen species

The catalytic oxidation of methane (CH4) stands as an essential strategy for curtailing greenhouse gas emissions. This study advances CH4 oxidation using Pd on La-doped CeO2, where water (H2O) boosts oxidation efficiency. The temperature for obtaining 50 % CH4 conversion on Pd/La-CeO2 catalyst was reduced from 288 °C (without H2O) to 260 °C (with H2O), while that on CeO2 was 570 °C both under conditions with and without H2O. Operando DRIFTS analysis reveals the reaction pathway and intermediates during CH4 oxidation. Ce cations provide adsorption sites for CH4, leading to the generation of CH3 adsorbed species with the help of surface O2–. La doping creates oxygen vacancies essential for oxygen activation and foster the formation of reactive hydroxide (OH) from adsorbed H2O and O. Pd contributes to the formation of more reactive oxygen species that facilitate OH generation at La cations and the oxidation of CH4 adsorption species to CO2 and H2O. The synergistic interplay between Pd and La-CeO2 is particularly noteworthy, with H2O also playing a role in the gasification of surface carbonates, thereby enhancing the overall performance of CH4 oxidation. A kinetic model based on the Langmuir-Hinshelwood mechanism is proposed, offering an insight into CH4 oxidation.

Sea surface carbon dioxide during early summer at the Tuandao nearshore time series site

To investigate air-sea CO2 flux at the Qingdao nearshore site and its temporal variations, a high-resolution continuous observation of surface carbon dioxide partial pressure (pCO2) was carried out at Zhongyuan Pier near Tuandao from May 25 to July 8, 2019. It was observed that during this period, surface pCO2 varied between ∼490 and ∼690 μatm, mainly associated with sea surface temperature. Surface pCO2 also displayed substantial diurnal variations, with an average amplitude of 64 ± 21 μatm, largely dominated by biological activities. During the observational period, this site acted as a source of atmospheric CO2, releasing 361 mmol CO2 m−2. The notable diurnal variations in air-sea CO2 flux, such as the observed average amplitude of 10.9 mmol m−2 d−1 in this study, pose a challenge for accurately estimating the air-sea CO2 flux in coastal regions without high-resolution observations.

Indole derivatives efficacy and kinetics for inhibiting carbon steel corrosion in sulfuric acid media

The global prevalence of metal corrosion is a significant challenge due to its detrimental effect. Environmentally friendly and non-hazardous alternatives for harmful and poisonous synthetic corrosion inhibitors are urgently necessary due to increasing environmental concerns and regulations prohibiting their application. In this study, indole molecules were employed as carbon steel corrosion inhibitors in acidic conditions. Gravimetrical and scanning electronic microscope (SEM) analysis was used in a preliminary investigation of indole as an organic inhibitor. The results revealed that adding indole to carbon steel before exposing it to sulfuric acid slowed and induced resistance to corrosion. The indole affixed themselves to the steel carbon surfaces, producing a barrier/protection for carbon steel. The efficacy of the indole in preventing corrosion was determined through the weight loss method. Temperature and inhibitory concentration effects on inhibition effectiveness under varying parameters were also reported. The temperatures employed were between 298 K and 328 K, while the inhibitor concentrations ranged from 1.2 × 10−3 M to 7.6 × 10−3 M, and both parameters significantly influenced corrosion inhibition effectiveness. The inhibitory mixture attained optimum efficacy in inhibiting corrosion, at 81 %, when the lowest and highest respective temperature and concentration were applied. The kinetic analysis was conducted under a range of temperatures to determine the reaction mechanisms of the inhibitor. The thermal adsorption isotherm of the inhibitor indicated that the surface adhered to Langmuir's adsorption isotherm. Additionally, investigations on corrosion and inhibition using the electrochemical impedance spectroscopy method (EIS) were conducted. This study can provide in-depth knowledge for advancing inhibitory science and engineering to enhance corrosion resistance in acidic media.

A synthesized field survey database of vegetation and active-layer properties for the Alaskan tundra (1972–2020)

Abstract. Studies in recent decades have shown strong evidence of physical and biological changes in the Arctic tundra, largely in response to rapid rates of warming. Given the important implications of these changes for ecosystem services, hydrology, surface energy balance, carbon budgets, and climate feedbacks, research on the trends and patterns of these changes is becoming increasingly important and can help better constrain estimates of local, regional, and global impacts as well as inform mitigation and adaptation strategies. Despite this great need, scientific understanding of tundra ecology and change remains limited, largely due to the inaccessibility of this region and less intensive studies compared to other terrestrial biomes. A synthesis of existing datasets from past field studies can make field data more accessible and open up possibilities for collaborative research as well as for investigating and informing future studies. Here, we synthesize field datasets of vegetation and active-layer properties from the Alaskan tundra, one of the most well-studied tundra regions. Given the potentially increasing intensive fire regimes in the tundra, fire history and severity attributes have been added to data points where available. The resulting database is a resource that future investigators can employ to analyze spatial and temporal patterns in soil, vegetation, and fire disturbance-related environmental variables across the Alaskan tundra. This database, titled the Synthesized Alaskan Tundra Field Database (SATFiD), can be accessed at the Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC) for Biogeochemical Dynamics (Chen et al., 2023: https://doi.org/10.3334/ORNLDAAC/2177).

Full-color biomass carbon dots for high-level information encryption and multi-color light emitting diode applications.

Six biomass carbon dots (BCDs) with adjustable emission from 450 to 680nm under a single wavelength excitation were successfully synthesized from spinach via solvent control strategy. The obtained BCDs show blue, green, yellow, violet, pink, and red emission with high photoluminescence quantum yield (PLQY = 12.68 ~ 30.77%). Detailed characterizations disclose that the tunable-emission mechanism is caused by the synergistic effect of carbon conjugate and surface oxidation degree. Meanwhile, full-color photoluminescence BCDs/PVP powder and BCDs/PVP/PVA films were fabricated by utilizing the prepared BCDs combined with polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA), respectively, which presented excellent high-level information encryption application. Importantly, multi-color and white light-emitting diode (LED) with Commission Internationale de L' Eclairage (CIE) of blue (0.25, 0.29); green (0.25, 0.31); yellow (0.42, 0.45); red (0.52, 0.31); and white (0.32, 0.31) were achieved by only using our prepared BCDs. This work provides a valuable strategy of preparing multi-color BCDs using readily available biomass materials and paves a way for high-level information encryption and LED applications.

Construction of a gradient cobblestone pattern on pyrolytic carbon surface for improved anti-thrombus

Surface modification is believed to be one of the most effective solutions to prevent thrombus formation associated with mechanical heart valves. Herein, we report, for the first time, the fabrication of a gradient cobblestone pattern on the pyrolytic carbon (PyC) surface aiming to improve its anti-thrombotic properties. A unique cobblestone pattern with gradient changing interspacing was generated on the PyC surface through laser etching. After coating with fluorosilane, the surface exhibited a water contact angle gradient ranging from 110 to 173°. The morphological and physicochemical properties, mechanical durability, drag reduction, in vitro anti-thrombotic properties, and in vivo biocompatibility of the surface were investigated to evaluate its potential as a heart valve replacement. It was found that the hydrophobic gradient wettability surface exhibited an excellent self-driving effect and mechanical durability, significantly reduced hemolysis rate and platelet adhesion, and prolonged coagulation time compared to the counterpart without gradient wettability. Furthermore, the gradient wettability surface demonstrated excellent in vivo biocompatibility. These findings are important for the design of artificial heart valves with improved anti-thrombotic performance.

Photolytic Degradation of Water‐Soluble Organic Carbon in Snowmelts: Changes in Molecular Characteristics, Brown Carbon Chromophores, and Radiative Effects

AbstractWater‐soluble organic carbon (WSOC) deposited in ambient snowpack play key roles in regional carbon cycle and surface energy budget, but the impacts of photo‐induced processes on its optical and chemical properties are poorly understood yet. In this study, melted samples of the seasonal snow collected from northern Xinjiang, northwestern China, were exposed to ultraviolet (UV) radiation to investigate the photolytic transformations of WSOC. Molecular characteristics and chemical composition of WSOC and its brown carbon (BrC) constituents were investigated using high‐performance liquid chromatography interfaced with a photodiode array detector and a high‐resolution mass spectrometer. Upon illumination, formation of nitrogen‐ and sulfur‐containing species with high molecular weight was observed in snow samples influenced by soil‐ and plant‐derived organics. In contrast, the representative sample collected from remote region showed the lowest molecular diversity and photolytic reactivity among all samples, in which no identified BrC chromophores decomposed upon illumination. Approximately 65% of chromophores in urban samples endured UV irradiation. However, most of BrC composed of phenolic/lignin‐derived compounds and flavonoids disappeared in the illuminated samples containing WSOC from soil‐ and plant‐related sources. Effects of the photochemical degradation of WSOC on the potential modulation of snow albedo were estimated. Apparent half‐lives of WSOC estimated as albedo reduction in 300–400 nm indicated 0.1–0.4 atmospheric equivalent days, which are shorter than typical photolysis half‐lives of ambient biomass smoke aerosol. This study provides new insights into the roles of WSOC in snow photochemistry and snow surface energy balance.

Functional carbon dots induced defect configuration entropy strengthening polyanion cathode for ultrafast-charging sodium ion batteries in a wide temperature

The development of fast-charging and wide-temperature sodium-ion batteries (SIBs) is of great significance to all-climate energy storage. However, the gigantic challenge lies in achieving super dynamic performance and stability of cathode materials. Herein, the defect configuration entropy (DCE) is conceptualized in Na3V2(PO4)3/carbon composite (NVP/C) cathode by manipulating heteroatoms and vacancies in the surface carbon layer. It is found that the bonding energy between the carbon layer and NVP interface increases with the DCE. Accompanying, the Na+ migration energy barrier is reduced and the electronic conductivity is enhanced, which are pivotal factors underpinning the low-temperature performance. Furthermore, the increase of DCE engenders the formation of a NaF-rich cathode-electrolyte interface, furnishing support for high-temperature stability. As a result, the DCE-strengthened NVP/carbon composite cathode exhibits a high capacity of ∼88 mAh g−1 at an ultrahigh rate of 200 C (13 s per charge process). Moreover, the superior electrochemical performance in the wide temperature range of −30–60 °C is achieved with 0.101 % capacity decay per cycle at −20 ℃, and 0.0047 % capacity decay per cycle at 60 ℃.

Systematic Investigations of Surface Oxygen Functional Groups on Spherical Hard Carbon for Sodium-Ion Batteries

The surface activity of hard carbons and its effect on the formation of a stable solid electrolyte interface (SEI) in sodium ion batteries has gained significant interest in the scientific community over the last years. The surface of hard carbons thus plays a pivotal role within the cell, as it constitutes the interface between the bulk material and the electrolyte. Following pyrolysis of the carbon-rich precursor at high temperatures, various oxygen functional groups (OFGs) and defects, such as five- or seven-membered rings, are present on the surface of the resulting hard carbons. The influence of OFGs on the surface is however controversially discussed. On the one hand, irreversible reactions of sodium ions with OFGs lower the initial coulombic efficiency (ICE), which leads to a decreased energy density. On the other hand, OFGs may also serve as nucleation sites for the SEI leading to a more conductive interfacial phase for sodium ions. Although many approaches of additional oxygen functionalization on the surface of hard carbons have already been reported, they mostly employ harsh reaction conditions disregarding the morphological impact on the carbon surface.In our studies, oxo-functionalized polycyclic aromatic hydrocarbons (PAHs) are adsorbed on the surface to serve as model OFGs on surface oxygen deficient hard carbons. The versatility of functionalized pyrenes in combination with nondestructive adsorption enables independent investigations on the oxygen functionalization of the hard carbon surface. In the first step, native surface oxygen groups are cleaved from the pristine hard carbon through a high-temperature post-treatment in hydrogen atmosphere. Afterwards, selective re-introduction of surface OFGs is achieved through adsorption of oxo-functionalized pyrene derivatives such as 1-hydroxypyrene or 1-pyrenecarboxylic acid to simulate hydroxy or carboxylic surface functionalities. Additionally, various spatially configurations of surface OFGs can be mimicked by elongating the distance between the oxygen functionality and the pyrene backbone through a short alkyl chain (e.g. 1-pyrenebutyric acid).Our systematic approach of selectively re-introducing surface OFGs allows the discrimination between different surface OFGs and their influence on the SEI. The surface of our modified hard carbons is characterized by X-Ray photoelectron spectroscopy (XPS) and Raman spectroscopy to evaluate the oxygen content and determine the defect concentration. The electrochemical performance is assessed by rate performance tests and cyclic voltammetry in three-electrode half-cells with sodium metal as counter and reference electrode. Initial findings validate the correlation between surface oxygen functionalization determined by XPS and the electrochemical formation potential of the SEI during the first cycle. After high-temperature treatment in a hydrogen atmosphere, the surface oxygen content decreases from ~5% to 2%, leading to a significant lowering of the plateau capacity. Simultaneously, the ICE decreases from 79% to 55%. Cyclic voltammetry of deoxygenated hard carbon reveals that the SEI formation potential is shifted from ~1.0 V vs. Na towards lower potentials of ~0.3 V vs. Na indicating that different decomposition products are formed. Furthermore, rate performance is substantially deteriorated by the development of a modified SEI. Ex-situ XPS of cycled electrodes and electrochemical impedance spectroscopy are used to identify differences in the SEI composition and link them to the electrochemical performance of our spherical hard carbons.Figure: 1-Pyrenebutyric acid adsorbed on the surface of hard carbon highlighting the different possible spatially orientations of the oxygen functional group. Figure 1

Pyrene Funtionlized Hollow Porous Carbon/S-Dib Composite As a Cathode for Lithium-Sulfur Batteries

Lithium-sulfur batteries (LiSBs) stand out as promising candidates for the next-generation energy storage system. However, challenges such as the “shuttling effects” of intermediate lithium polysulfides and sluggish conversion between sulfur and lithium sulfide have led to low specific capacity under high current and a shortened cycling life for LiSBs. Extensive research has explored porous carbon materials as hosts for sulfur in LiSBs cathodes. Nevertheless, overcoming the “shuttling effects” and ensuring the uniform deposition of lithium sulfide without using metals or metal-containing species remains a challenge.Taking advantage of its aromatic properties, which promotes robust π-π interactions with sp2-hybridized carbon, pyrene with various functionalized groups emerges as a viable solution for surface modification through non-covalent bonding to carbon. In this study, we present the synthesis of X-pyrene (X=OH, NH2, Cl) modified hollow porous carbon (HPC) serving as a micro-reactor for inverse vulcanization, resulting in the formation of S-DIB/X-HPC (X=OH, NH2, Cl) with a uniform structure. Abundant oxygen-, nitrogen- and chloride interfaces were designed to act as adsorption catalytic sites, accelerating conversion kinetics and mitigating shuttle effects.Hollow porous carbon (HPC) nanoparticles were prepared from ZIF-8 by carbonization at 950 °C under argon atmosphere. (Figure 1a). The cross-sectional view in Figure 1b reveals numerous individual hexagonal structures with abundant internal pores. This structure helps accommodate inverse vulcanization (IV) reactions and ensures the uniform distribution of the final product (S-DIB). To evaluate the adsorption quantity of pyrene on the carbon surface, standard solutions of varying pyrene concentrations in dimethyl sulfoxide (DMSO) were prepared and analyzed using Ultraviolet–visible spectroscopy (UV-VIS). A linear relationship is fitted between the intensity of these peaks with the standard pyrene solution. Therefore, the concentration in the filtrate is verified to be approximately 2 mM, in contrast to the initial concentration of 10 mM before adsorption. This observed concentration decrease implies an effective adsorption of pyrene molecules onto the HPC surface. To further investigate the catalytic effect of Cl-pyrene and NH2-pyrene for sulfur redox reactions, potentiostatic nucleation of Li2S on the HPC, Cl-HPC and NH2-HPC electrodes were conducted to clarify the involved multiphase transition process. As shown in Figure 3, the capacity of precipitated Li2S on Cl-HPC (160.62 mAh gS −1) and NH2-HPC (135.75 mAh gS −1) are both higher than that on HPC (99. 93 mAh gS −1). As a result, superior to S-DIB/HPC, the S-DIB/Cl-HPC cathode exhibits a higher initial specific capacity of 1208 mA h g−1 at 0.1 C and a capacity of 643 mA h g−1 at 3 C, and still retain 913 mAh g−1 while returning to 0.1 C. Furthermore, the S-DIB/NH2-HPC cathode possesses excellent cyclability with a high capacity retention of 652 mAh g−1 at 1 C over 300 cycles, yielding an average capacity decline of only 0.076% per cycle. Additionally, we investigate the impact of native surface groups on the deposition of lithium sulfide and the conversion of polysulfides. Figure 1

All-Diamond Boron-Doped Microelectrodes for Neurochemical Sensing with Fast-Scan Cyclic Voltammetry.

Neurochemical sensing with implantable devices has gained remarkable attention over the last few decades. A promising area of this research is the progress of novel electrodes as electrochemical tools for neurotransmitter detection in the brain. The boron-doped diamond (BDD) electrode is one such candidate that previously has been reported for its excellent electrochemical properties, including a wide working potential, superior chemical inertness and mechanical stability, good biocompatibility and resistance to fouling. Meanwhile, limited research has been conducted on the BDD as a microelectrode for neurochemical detection. Our team has developed a freestanding, all diamond microelectrode consisting of a boron-doped polycrystalline diamond core, encapsulated in an insulating polycrystalline diamond shell, with a cleaved planar tip for electrochemical sensing. This all-diamond electrode is advantageous due to its - (1) batch fabrication using wafer technology that eliminates traditional hand fabrication errors and inconsistencies, (2) absence of metal-based wires, or foundations, to improve biocompatibility and flexibility, and (3) sp 3 carbon surface with resistance to biofouling, i.e. adsorption of proteins or unwanted molecules at the electrode surface in a biological environment that impedes overall electrode performance. Here, we provide findings on further in vitro testing and development of the freestanding boron-doped diamond microelectrode (BDDME) for neurotransmitter detection using fast scan cyclic voltammetry (FSCV). In this report, we elaborate on - 1) an updated fabrication scheme and work flow to generate all diamond BDDMEs, 2) slow scan cyclic voltammetry measurements of reference and target analytes to understand basic electrochemical behavior of the electrode, and 3) FSCV characterization of common neurotransmitters, and overall favorability of serotonin (5-HT) detection. The BDDME showed a 2-fold increased FSCV response for 5-HT in comparison to dopamine (DA), with a limit of detection of 0.16 µM for 5-HT and 0.26 µM for DA. These results are intended to expand on the development of the next generation BDDME and guide future in vivo experiments, adding to the growing body of literature on implantable devices for neurochemical sensing.

Enhancing Electrochemical Sensor Performance: Studies of Electrodes Tailored with ZnO/ZnFe2O4 Nanoparticles

Spinel metal oxides possess excellent magnetic, electrical, and optical properties. They take AB2O4 (face centered cubic) form with oxygen anions providing tetrahedral (Td) and octahedral (Oh) sites for A+2 and B+3 cations. Spinel can have a normal, inverse, or mixed form based on the occupancy of different cations in Td and Oh sites. The peculiarity of the spinel crystal structure is that its composition can be easily modified without affecting the crystal structure based on the type of cation. The type of cation in the composition defines if the spinel has a normal or inverse form [1]. Based on these premises, we have already synthesized ZnxNi1-xFe2O4 (x =0, 0.2, 0.4, 0.6, 0.8, 1) nanomaterials achieving a clear gradual transition from inverse (x=0) to normal (x=1) spinel. Synthesized nanomaterials were employed as mediators in electron transfer between the screen-printed carbon working electrode and paracetamol to understand the effect of chemical composition and crystal structure on the electron transfer at the electrochemical interface [1]. Normal spinel ZnFe2O4 was found to be the best nanomaterial in terms of sensitivity and kinetic rate constant. In further works, with the aim to understand the effect of ionic radii on sensitivity and electron transfer rate constant in electrochemical sensing of paracetamol, we have focused on the normal spinel structure and modified the composition by varying the concentration of Fe3+ with Cr3+ and Bi3+ [2,3]. This study also proved that the normal spinel ZnFe2O4 has the highest sensitivity and electron transfer rate constant towards paracetamol sensing.In this work, we will present the synergic effect that can be obtained by interfacing ZnFe2O4 with ZnO nanomaterials by tuning the band gap of the heterogeneous structure. The aim is to understand the effect of band gap on sensitivity and electron transfer rate constant in electrochemical sensing. ZnFe2O4, ZnO, and ZnO/ZnFe2O4 nanomaterials are synthesized by a simple, single step auto combustion technique using the respective metal nitrates as precursors. Nanomaterial morphology and particles size are investigated by scanning electron microscopy. X-ray diffraction technique is employed to analyze the crystal structure and identify different phases in the newly synthesized materials. Then, commercially available screen-printed carbon electrodes with carbon working electrode and carbon counter electrodes are used for the electrochemical measurements in combination with an external double junction Ag/AgCl as a reference electrode. The synthesized nanomaterials are mixed with 1-butanol and a 5 μL solution is used to modify the surface of the carbon working electrode to mediate the redox reactions between the carbon surface and the molecule of interest. Primarily the sensors are characterized using cyclic voltammetry with ferri/ferrocyanide redox couple as a probe molecule. Improvement in sensitivity is observed for ZnFe2O4 (8.85 ± 0.50 μA/mM), ZnO (8.50 ± 0.30 μA/mM), and ZnO/ZnFe2O4 (8.22 ± 0.16 μA/mM) sensors compared to the bare carbon one (6.30 ± 0.40 μA/mM). By performing cyclic voltammetry at different scan rates (ν) from 25 to 125 mV/s, a good linearity of redox currents with respect to v0.5 is observed and redox peak positions are varying linearly with ln(ν). Peak-to-peak separation (ΔEp) is reduced for ZnO/ZnFe2O4 sensors compared to the carbon one. All these results suggest a faster electron transfer at the interface when the modified electrodes are used. Laviron model is employed to calculate the electron transfer rate coefficient and constant. The rate constant for ZnFe2O4 (41.8 ± 2.6 ms-1), ZnO (46.0 ± 4.0 ms-1), and ZnO/ZnFe2O4 (33.1 ± 4.5 ms-1) sensors is 3 to 5 times higher as compared to the bare carbon one (9.97 ± 0.78 ms-1). We are currently studying the potential application of ZnO/ZnFe2O4 nanomaterials in electrochemical sensing of small molecules relevant in biomedical field (dissolved oxygen, pH) and pharmaceutical drugs (paracetamol) to assess the potential for their use in different clinical settings.

Relationship between Roughness and Wettability of Nine Types of Implant Surfaces and Potential Interference of Surface Oxygen and Carbon: In Vitro Evaluation.

Aim: To assess the roughness and hydrophilicity of nine types of dental implant surfaces, while also examining the presence of contaminants carbon and oxygen on these surfaces. Furthermore, the study investigated potential correlations between these characteristics across the analyzed surfaces. Materials and Methods: The surfaces analyzed were as follows: MI: machined (turned), Implacil implant; TOI: blasted with titanium oxide, Implacil implant; TOAEI: blasted with titanium oxide and acid-etched, Implacil implant; ZAED: blasted with zirconia and acid-etched, DSP implant; CPD: coated with calcium phosphate, DSP implant; XD: subjected to an experimental treatment (patent pending), DSP implant; DAEHAS: double acid-etched and activated with hydroxyapatite nano-crystals, SIN implant; DAES: double acid-etched, SIN implant; and AMP: untreated surface of the Plenum implant, produced by additive manufacturing. Four and five disc-shaped specimens were used in the hydrophilicity and roughness assessments, respectively. Roughness was evaluated by optical profilometry and scanning electron microscopy; hydrophilicity was determined using the sessile-drop technique; and the chemical analysis was performed using X-ray photoelectron spectroscopy. The Kruskal- Wallis, Mann-Whitney, and Spearman correlation tests were employed to analyze the data (p < 0.10). Results: Significant differences were observed among the analyzed surfaces in terms of both roughness and hydrophilicity (p < 0.001). The surface exhibiting the highest roughness was AMP, whereas the greatest hydrophilicity was exhibited by CPD. Correlations between roughness and hydrophobicity were observed for MI (r = 0.936, p = 0.009), ZAED (r = 0.957, p = 0.004), and DAES (r = 0.964, p = 0.005). The carbon concentration observed on the CPD surface was lower than that observed on the other surfaces, whereas the oxygen concentrations were similar. No correlations were observed between the presence of contaminants and the roughness or hydrophilicity characteristics. Conclusion: Roughness and hydrophilicity values exhibited considerable variation among the tested surfaces. Aside from the CPD surface, comparable concentrations of carbon and oxygen were detected. Although correlations between roughness and hydrophilicity were observed only for the ZAED, DAES, and MI surfaces, these correlations were inadequate to establish a causal relationship between the two surface characteristics.

Preparation of Biomass-Derived High Specific Surface Area Carbon with Titanium Nitride Nanoparticles for Lithium-Sulfur Batteries

The widespread challenges facing lithium-sulfur batteries, including the low electrical conductivity of sulfur and its species, electrode volume fluctuations during cycling, and the lithium polysulfides shuttle effect, have hindered their commercialization and practical utility [1,2].Our study addresses these issues by incorporating titanium nitride (TiN) nanoparticles onto high specific surface area porous carbon, exploring this composite's potential as both a sulfur cathode host and separator modifier. The synthesis of the carbon/TiN composite involved two key stages: firstly, the in-situ growth of titanium dioxide (TiO2) nanoparticles on the carbon surface utilizing titanium tetrachloride as a precursor; secondly, the conversion of the TiO2 nanoparticles to TiN nanoparticles through carbothermal nitridization (thermal treatment at 1400 ℃ for 4 hours in a nitrogen medium) [3,4].The lithium-sulfur cell employing the prepared C/TiN-25%@S cathode exhibited an initial discharge capacity of 1155 mAh g-1 at 0.2 C, maintaining a capacity exceeding 700 mAh g-1 after 100 cycles. Notably, the lithium-sulfur cell utilizing the C/TiN-25%@S cathode and a C/TiN-modified separator demonstrated enhanced cycling performance, delivering an initial discharge capacity of 1623 mAh g-1 with retention of over 1126 mAh g-1 after 100 charge/discharge cycles at 0.2 C. Acknowledgments This research was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP19677708).

Boron-Doped Carbon Scaffold Hosts for Li Metal Batteries

Lithium metal anodes offer the promise of higher energy density batteries. However, the formation of lithium dendrites due to non-uniform plating and stripping of the lithium metal has proven to be a major hurdle for this technology, decreasing the lifetime of the device and causing safety hazards. Utilizing a carbon scaffold host for the lithium metal anode can limit dendrite formation by providing a more uniform electric field and numerous lithium nucleation sites to encourage uniform plating and stripping. In this poster, we present our work developing carbon scaffold hosts for lithium metal anodes. We synthesized scaffolds with various architectures and microstructures using different carbon materials. Our atomistic simulations demonstrated that the addition of boron to the carbon results in stronger binding of lithium to the carbon surface, further improving the lithiophilicity. Therefore, we also prepared boron-doped carbon scaffolds to test this experimentally. Boron was introduced using boric acid and incorporated into the carbon structure during carbonization under nitrogen, and these samples were characterized by XPS, SEM, and BET to try and correlate scaffold properties with performance. In addition, we are investigating other dopants (such as nitrogen), which have also been reported to increase the lithiophilicity of carbon materials. Utilizing these doped carbon scaffolds can help increase the lifetime of lithium metal batteries by improving the cycling uniformity.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344

(Keynote) High-Performance Carbon Nanotube Transistors for Logic Platform

Low-dimensional 1D and 2D materials hold promise as candidate channel materials for highly scaled and high-performance transistors beyond the limits of silicon-based transistors. This talk will first motivate transistors built on low-dimensional channels due to the significant speed, energy efficiency, and transistor density benefits enabled by their electronic and physical properties. This talk will focus on 1D carbon nanotube (CNT) semiconductors and describe the advanced device component process modules that have been demonstrated, explaining both the fundamental mechanisms of operation and device-level performance objectives. Single-CNT FET experimental studies give insight into the quality of (1) low resistance N- and P- contacts down to 10 nm contact length, (2) high-capacitance gate dielectrics optimized for deposition on SP2 carbon surfaces, and (3) controlled N- and P- remote dielectric doping. To achieve high current density each transistor must contain multiple CNTs, therefore we will review state-of-the-art strategies to assemble densely aligned arrays of CNT with controlled CNT spacing between 2-10 nm and uniform electronic bandgap. The final portion of the talk will highlight recent advances from our team and others to integrate the best device components together to demonstrate high-performance carbon nanotube MOSFETs. We will elaborate on the remaining challenges and provide a summary of device design tradeoffs that will help guide future studies.We are grateful for support and collaboration from TSMC Corporate Research, DoD, Stanford SystemX Alliance, Stanford Nanofabrication Facility, Stanford Nano Shared Facility, and the University of California at San Diego.

The Heterogeneity of Turn-over Number in Electrocatalysis

Chemical catalysts dominate the multi-billion global revenue of the chemical industry because they accelerate the time it takes a particular reaction to reach equilibrium without altering the equilibrium constant. Electrocatalysis can provide significant benefits compared to other methods, as it has minimal purification and separation costs, is operational at low temperatures and pressures, replaces hazardous and toxic chemical sources with electric current, and can be integrated with renewable energy sources. From a techno-economical point of view, some considerations are critical during a catalyst design: cost, activity, and durability. One useful metric to quantify catalyst durability is turn-over number (TON), which represents the maximum yield of products attainable from a catalytic center. Mathematically speaking, the TON is defined as: TON = ∫0 ∞ TOF(t) dt, where TOF is the turn-over frequency, which is the rate of turn-overs (N) per active site. Currently, without any exception, the TON is given as a fixed number describing the total amount of substrate converted until the catalysts fully degrade. Our approach studies electrocatalytic deactivation processes at the single catalyst level using a technique entitled single-entity electrochemistry for freely diffusing catalysts. The hydrogen evolution reaction (HER) is investigated with platinum nanoparticles as the model catalyst because it deactivates at the nanoscale when the catalytic activity decreases over time. At specific applied potentials, the current measured when a single platinum nanoparticle impacts the electrode creates a transient spike and decay back to the baseline current. TON is quantified by fitting the current decay response and integrating above the fit to find the charge transferred to catalyze the reaction. Our results show that electrocatalyst degradation and TON have a distribution, where some catalysts are more stable than others, and depends on the applied potential and size of the nanoparticles. In order to study how the surface facets of platinum affect the TON, SECCM was coupled with scanning electron microscopy (SEM) to compare the deactivation of a polycrystalline platinum surface in the macro scale with immobilized platinum nanoparticles on a glassy carbon surface. Combining local structural, electrochemical activity, and durability will bridge our fundamental understanding of macro and nanoscale catalyst deactivation processes to assist in the bottom-up approach of material development and design of large-scale industrial electrocatalysts.

Carbon removal flotation performance and economic analysis of different coal fly ash using waste fried oil as a collector

Collector consumption in flotation is significant, and petrochemicals like kerosene, being non-renewable and expensive, are commonly used collectors; therefore, finding suitable alternatives to reduce costs is essential. Waste fried oil (WFO) possesses properties similar to those of kerosene, making it a viable substitute for flotation processes. In this study, the flotation performance was analyzed and economic analysis of WFO as a collector was performed for circulating fluidized bed furnace fly ash (CFBFA) and pulverized coal furnace fly ash (PCFFA). The interaction mechanism between WFO and fly ash was analyzed using contact angle, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) tests. The findings revealed that the optimal WFO dosage for coal fly ash closely correlates with the combustion technology used to obtain it. The study also established well-fitted curves for the loss on ignition (LOI) of CFBFA and PCFFA with changes in WFO dosage. FTIR and XPS analyses revealed that the interaction of WFO carbon chains with nonpolar regions on the surface of unburned carbon in coal fly ash resulted in an increase in hydrophobic carbon chain groups on the surface of unburned carbon, and the combination of oxygen-containing groups in WFO with the hydrophilic sites on the surface of unburned carbon were the main reasons for the enhancement of hydrophobicity of unburned carbon particles. Moreover, the economic analysis revealed that flotation of 1 t of CFBFA and PCFFA with WFO can yield profits of 1.91 USD and 1.11 USD more, respectively, compared with kerosene, which has practical applications in industry.

Synergistic activation of hydroxyl groups by hierarchical acid sites and deep eutectic solvents for the dehydration of fructose to 5-hydroxymethylfurfural under mild temperature

The activation of C–OH bond shows great importance for fructose dehydration to produce 5-hydroxymethylfurfural (HMF). In the deep eutectic solvent (DES), the synergistic improvement of surface sulfonic acid groups on hierarchical porous carbon solid acids (HPCSA) and choline chloride (ChCl) on activation of fructose hydroxyl groups was studied to achieve high catalytic performance under mild conditions. The results show a high yield of 90.7 % for HMF at relatively mild temperature of 70 °C. The polarizing effect of ChCl on fructose hydroxyl groups enhances the interaction energy between fructose and sulfonic acid groups on carbon surface, resulting in elongated C–OH bond of fructose from 1.412 Å to 1.456 Å. The hierarchical pore structure can improve the accessibility to acid active sites and increase the quantity of surface sulfonic acid groups by enlarging specific surface areas. A reaction mechanism considering the synergistic effect of various components in DES is proposed to explain the promotion of fructose dehydration under mild conditions. This work provides an effective solution for utilizing biomass to produce renewable energy.

Spatial variability of mineral surface area and carbon sequestration potential at the farm scale – a case study

Spatial variability of mineral surface area and carbon sequestration potential at the farm scale – a case study