bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Post Nitridation Annealing on Thermally Grown Silicon Oxynitride Characteristics
Authors: Vaid Rakesh , Rajput Renu , Khosla Ajit
Published: February 2020

The ability to block the direct current is one of the main requisite for the gate dielectric in a metal-oxide-field-effect-transistor. Since thickness of oxide is inversely related with oxide capacitance, therefore oxide capacitance can be increased as an alternative to oxide thickness to meet the scaling requirements. Oxynitrides and high-k materials as gate dielectric have been considered as promising candidates to overcome the above problems. At greater physical thickness, these materials have the similar capacitance value which avoids tunneling effect. SiON has been used as a substitute for SiO2 because of its high dielectric permittivity and low density of surface states. In this paper, the effect of post nitridation annealing on thermally grown silicon oxynitride characteristics have been investigated by analyzing high-frequency capacitance-voltage (C-V) and current- voltage characteristics (I-V) of n-Si/SiON/Ti-Pt MOS capacitor. Post nitridation annealing was carried out at 800°C for 15 min in Nitrogen (N2) ambient. Ellipsometery, FESEM, Atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) was used to study the effect of post nitridation annealing on the physical characteristics of deposited silicon oxynitride film. Cheung’s approach has been used for evaluating barrier height (ϕbo
) and ideality factor (η). We present a comparative study between the as-deposited and annealed film and it was found that the physical and electrical properties (k, η, ϕbo
etc) improved by post nitridation annealing is attributed to the improvement in the interface properties of Si/SiON. Moreover, the value of positive fixed charge density (Q
f ~1.8×1012 cm−2) is effective for field-effect passivation of n-type Si surfaces. For both as-deposited and annealed SiON film, the maximum current through the Si/SiON/Ti-Pt device never exceeded a value of 10–8A/cm2 which indicates that the ﬁlm were very good insulators. These results indicate that the obtained SiON film is an appropriate gate insulator for advanced nano electronic devices.
(Plenary) 4D Printing for Sensors and Energy Applications
Authors: Thundat Thomas , Khosla Ajit , Furukawa Hidemitsu
Published: February 2020

Sustained advances in 3D printing techniques have resulted in the emergence of 4D printing that incorporates additional dimension where stimuli-responsive smart materials change the shape of the printed structure. Unlike the 3D printed structures, a 4D printed structure evolves as a function of time. The mechanical and structural properties of a 4D printed structure can be pre-programmed using a combination of material properties and computational modeling. We have shown that it is possible to print structures that are electrically conducting. This electrically conducting structure can be transformed under physical stimuli into an active circuit element. Such circuit elements can be the basis for transferring electrical power using single contact, single conductor concept for powering sensors. Stimuli dependent shape can be used for tuning the electrical resonance of single conductor electrical transmission. This single conductor, single contact power delivery also offers opportunities for imbedded sensors in 3D and 4D printed structures. It is also possible to use similar 4D printed structures for developing tunable structures for target analyte pre-concentrators for enhancing the sensitivity of sensors. These 4D printed structures will have myriads of applications in chemical sensing. Our recent results will be presented. We will also address the challenges and opportunities for their future applications.
(Invited) Si Materials for Li-ion Battery Negative Electrode Applications
Authors: Liu Gao
Published: February 2020

Silicon is an attractive candidate for lithium-ion batteries negative electrode materials because it delivers 10 times greater theoretical (~4200 mAh/g) specific capacity than that of traditional graphite anode (~370 mAh/g). However, the widespread application of silicon materials has remained to be a significant challenge, originating from large volume changes during lithium insertion and extraction processes and excessive surface reaction with electrolyte. This large volume change causes cracking and pulverization of silicon, leading to loss of the electrical contact in the electrode. The Si volume change coupled with excessive electrolyte surface reaction, leads to drastic capacity fading.

To address the large volume change, new electrode fabrication approaches have been developed such as nano-Si materials assembly and new binder development. New functional binders with electronic conductivity, adhesive functional groups, and crosslinking functional groups are the recent research focuses.

To address the excessive surface reactions of Si with electrolyte, electrolyte additives of different chemistry has been developed and tested. Fluorocarbon additives such as FEC have demonstrated as an effective SEI formation additive for Si materials. Electrolyte additives for Si materials has been a very active area of research. Electrolyte additives with due functionalities have attract major interest lately.

Si particle coatings such carbon coating as an electric conductive medium and electrolyte insulating buffering layer have been widely used to encapsulate the silicon particles and prevent electrolyte reaction. There are many different carbon precursors for performing the carbon coating, which produce carbon coatings with different chemical and morphological carbon coatings. The Si materials with highly graphitized and dense coating is able to not only deliver higher gravimetric capacity and stable cycling compared to that of the Si with disordered carbon coating, but also alter the Si materials bulk transformation.

A comprehensive discussion of the Si materials coating, electrode design and electrolyte additives and its electrochemical performance will be presented.
Realizing an Asymmetric Supercapacitor Employing Carbon Nanotubes Anchored to Mn3O4 Cathode and Fe3O4 Anode
Authors: Kumar Ankit , Sarkar Debasish , Mukherjee Soham , Patil Satish , D. Sarma D. , Shukla Ashok Kumar
Published: February 2020

A facile route to anchor pseudocapacitive materials on multi-walled Carbon Nanotubes (CNTs) to realize high-performance electrode materials for Asymmetric Supercapacitors (ASCs) is reported. The anchoring process is developed subsequent to direct decomposition of metal-hexacyanoferrate complex on the CNT surface. Transmission electron microscopy (TEM) analysis reveals that the nanoparticles (NPs) are discretely attached over CNT surface without forming a uniform layer, thus making nearly entire NP surface available for electrochemical reactions. Accordingly, CNT-Mn3O4 nanocomposite cathode shows significantly improved capacitive performance as compared to pristine CNT electrode, validating the efficacy of designing the composite electrode. With CNT-Fe3O4 nanocomposite as paired anode, the hybrid ASC delivers a specific capacitance of 135.2 F/g at a scan rate of 10 mV/s within a potential window of 0-1.8V in the aqueous electrolyte and retains almost 100% of its initial capacitance after 15000 cycles. The serially connected ASCs can power commercial LEDs and mobile phones reflecting their potential in next-generation storage applications.
Alkali Metal Chlorides Based Hydrogel As Eco-Friendly Neutral Electrolyte for Bendable Solid-State Capacitor
Authors: Li Hu , Li Zhou , Fan Yubo
Published: February 2020

Hydration greatly affects ionic state in an aqueous environment and thus influences their electrochemical performance. In this study, three alkali metal chlorides dissolved in neutral polyvinyl alcohol hydrogel are fully investigated for bendable solid-state TiO2 nanotube capacitor (BSTC). Radius difference between bare ions and hydrated ions results in their obviously different electrochemical performance. Hydration makes lithium-ion (Li+) possess the largest hydrated radius and the lowest mobility, which endows it the best capacitance performance in BSTC by electrochemical characterization. BSTC with hydrated Li+ achieves high capacitance retention rates of 87% at 1V for 3000 cycles and of 70% at 2V for 2500 cycles. Additionally, it has no significant capacitance variation when stored for one month or bended to 120°.
Towards an Atomic-Level Understanding of Solid Electrolyte Interphase Formation through Molecular Simulation
Authors: Boyer Mathew J , Hwang Gyeong S
Published: February 2020

Lithium ion batteries (LIBs) have been one of the greatest technological achievements in recent history, allowing for leaps forward in consumer technologies. However, growing demand for electric vehicles worldwide is fueling demand for LIBs with larger capacity, faster charging, and longer cycle lives without compromising on safety. This has prompted a resurgence in the study of lithium metal as a next-generation anode, despite challenges with stabilization of the anode-electrolyte interface and the formation of dendrites. In order to realize the large theoretical capacity offered by lithium metal as an anode material, the interface must be engineered to allow for stable cycling through the in situ formation of an ionic conducting and electrically insulating surface layer known as the solid electrolyte interphase (SEI) by reductive decomposition of the electrolyte. While formation of a stable SEI remains an issue in the advancement of next-generation batteries, a fundamental understanding of the process at the graphite electrode/electrolyte interface remains elusive despite its ubiquity in commercial LIBs. The time- and size-scales at which the SEI is formed makes its study experimentally difficult at the appropriate resolution for the underlying phenomena which are critical to determining its composition, morphology, and properties. In order to build an atomic-level understanding of the SEI formation process, we have utilized molecular dynamics (MD) simulations with both classical force fields and density functional theory (DFT) to explore the reaction and transport processes which occur at the anode/electrolyte interface including reduction of ethylene carbonate (EC), intermediate diffusion near the electrode surface, and subsequent chemical reaction of the intermediate species. We have explored the effects of acyclic carbonates on reactions kinetics and interfacial structure as well the effects of some common additives. In this talk, we will present some of our recent findings on how local structure of the electrolyte influences reaction kinetics and transport processes which lead to the aggregation and precipitation of reduced carbonate solvents to form the SEI. This improved understanding of the underlying processes which contribute to the formation of the SEI on graphite electrodes may not only improve engineering of such interfaces in commercial applications, but also generate new ideas in the pursuit of a stable lithium/electrolyte interface.
K2[(VO)2(HPO4)2(C2O4)] and K
x
VOPO4
as 4 V-Class Positive Electrode Materials for K-Ion Batteries
Authors: Abdulrahman Shahul Hameed , Katogi Akihiro , Kubota Kei , Komaba Shinichi
Published: February 2020

K-ion batteries (KIBs) potentially operate at high-voltage and high-current thanks to the lower standard electrode potential of K/K+ and the lower solvation energy than those of Li/Li+ in organic electrolytes and fast K-ion diffusion.[1] To realize practical applications, high energy density positive electrode materials are, however, indispensable. In this study, two vanadium based positive electrode materials with layered structure, namely, K2[(VO)2(HPO4)2(C2O4)] and and K
x
VOPO4 are synthesized and their electrode performances are examined in potassium cells. Highly reversible Li insertion/extraction oxalatophosphate material was reported with reversible capacities of >100 mAh g-1 and with a high voltage operation of ~3.8 V vs. Li/Li+. [2, 3] Hence, reversible K extraction/insertion and high voltage operation are expected in K cells.

K2[(VO)2(HPO4)2(C2O4)] was prepared by a simple precipitation method at room temperature. As shown in Fig. 1, K2[(VO)2(HPO4)2(C2O4)] delivers a reversible capacity of ~90 mAh g-1 in the K-half cell at 0.1 C in the voltage range of 2.5 - 4.5 V vs. K/K+ and excellent cycle stability is demonstrated. Furthermore, high rate capability with 76 mAh g-1 at 10 C is achieved by optimization of the electrolyte composition. Another vanadium-based layered positive electrode material, K
x
VOPO4 was also prepared by a precipitation method at room temperature. By optimization with carbon-coating and ball-milling, the material delivers a reversible capacity of 80 mAh g-1 at 3.7 V for over 200 cycles.

Fig.1: Voltage profiles and capacity retention plots of K2[(VO)2(HPO4)2(C2O4)] in a K-half cell.

References

[1] K. Kubota, S. Komaba, et al., Chem. Rec., 2018, 18, 459-479.

[2] A.S. Hameed et al., Sci. Rep., 2015, 5, 16270.

[3] A.S. Hameed et al., J. Mater. Chem. A, 2013, 1, 5721-5726.

Figure 1
Red Phosphorus-Based Materials As Anode for Na-Ion Batteries K-Ion Batteries
Authors: Yu Yan
Published: February 2020

Recently, sodium ion batteries (NIBs) and potassium-ion battery (KIBs) have been attracted much attention since sodium and potassium resource is natural abundant, environmental friendly and showing similar chemical properties with lithium ion batteries. The red P anode for Na-ion and K-ion batteries has attracted great attention recently due to the high theoretical capacity, but the poor intrinsic electronic conductivity and large volume expansion restrains its widespread applications. The intrinsic low electronic conductivity of red P leads to the poor electronic kinetics, large polarization and further low active material utilization. In addition, the large volume expansion (~400%) during Na insertion/extraction in red P leads to pulverization of red P and loose contact between the red P and the current collector, resulting in the severe capacity fading.

Herein, we successfully encapsulate the red P into the carbon-based material (such as MOF-derived carbon, N-doped carbon, carbon-nanofibers) via the vaporization-condensation method.1, 2 Superior cycling stability (high capacity retention of about 93% at 2 A g-1 after 100 cycles) and excellent rate performance (502 mAh g-1 at 10 A g-1) could be obtained for the P/C electrode. The superior electrochemical performance could be ascribed to the successful incorporation of red P into the unique carbon matrix with large surface area and pore volume, interconnected porous structure, excellent electronic conductivity and superior structural stability.The porous carbon matrix with abundant micro/meso pores, large pore volume could effectively facilitate the infiltration of the electrolyte, and accommodate large volume expansion of red P during electrochemical process. The excellent conductivity of the carbon could ensure the essential electrical contact to the insulating red P, leading to excellent sodium storage performances. The rational design of the unique red P/ carbon structure could be served as a model for other anode material with poor intrinsic electronic conductivity and large volume expansion.

References:

Wu, Y.; Liu, Z.; Zhong, X.; Cheng, X.; Fan, Z.; Yu, Y., Amorphous Red Phosphorus Embedded in Sandwiched Porous Carbon Enabling Superior Sodium Storage Performances. Small
2018,
14, (12), 1703472.

Li, W.; Hu, S.; Luo, X.; Li, Z.; Sun, X.; Li, M.; Liu, F.; Yu, Y., Confined Amorphous Red Phosphorus in MOF-Derived N-Doped Microporous Carbon as a Superior Anode for Sodium-Ion Battery. Advanced Materials
2017,
29, (16), 1605820.
Analysis of Solid-State Electrolytes for Li-Ion Batteries Using a Multiscale Molecular Dynamics Approach
Authors: Seminario Jorge M. , Galvez-Aranda Diego Eduardo , Ponce Victor , Selis Luis , Vicharra Cristhian , Franco-Gallo Franz , Gamero T Milenka
Published: February 2020

Metal lithium anodes are excellent alternatives for Li-ion batteries; however, nonuniform plating and swelling of the anode upon lithiation causes the growth of lithium dendrites, among few other problems. One possible solution to this, and perhaps the other problems, is the use of solid-state electrolytes. Our approach to analyze the use of solid-state electrolytes is based on performing a multiscale computational approach using quantum and classical molecular dynamics simulation techniques. We will present our study of the properties of the two above new types of materials for anodes and electrolytes as parts of a full nanobattery,1-4 whereby the properties of their solid electrolyte interphases will be determined. The speciation of several interfaces of lithium-metal anodes with electrolytes such as sulfides, halogenated phosphor-sulfides, halogenated nitrades, and few others of present interest will be presented. Since these simulations require the use of full nanobatteries, thus, they also require the presence of a cathode, and since sulfur and spinel structures are also potential alternatives, we will use related cathodes in our nanobatteries.

Selis, L. A.; Seminario, J. M., Dendrite Formation in Anodes of Lithium-Ion Batteries. RSC – Advances, 2018, 8, 5255-5267.

Galvez-Aranda, D. E.; Seminario, J. M., Simulations of a LiF Solid Electrolyte Interphase Cracking on Silicon Anodes Using Molecular Dynamics. J. Electrochem. Soc. 2018, 165, A717-A730.

Ponce, V.; Galvez-Aranda, D. E.; Seminario, J. M., Analysis of a Li-Ion Nanobattery with Graphite Anode Using Molecular Dynamics Simulations. J. Phys. Chem. C 2017, 121, 12959–12971.

Galvez-Aranda, D. E.; Ponce, V.; Seminario, J. M., Molecular Dynamics Simulations of the First Charge of a Li-Ion—Si-Anode Nanobattery. J. Mol. Model. 2017, 23, 120.
Effect of Titanium Disulfide Cathode Additive in the Performance of Li-S Batteries
Authors: Pandey Gaind P. , Adams Jada Imari , Callaway Jumia , Meda Lamartine
Published: February 2020

Lithium-sulfur (Li-S) batteries have attracted considerable attention as one of the most promising next-generation energy storage system owing to the high theoretical specific capacity (1675 mAh g-1), low cost, natural abundance and environmentally benign nature of sulfur. However, the poor electrical conductivity of elemental S results in low utilization of S specific capacity, and hence, insufficient specific energy of Li-S batteries. Development of Li-S batteries is hindered by sluggish kinetics resulting from the intrinsic poor conductivity of sulfur and capacity degradation due to solubility of polysulfides intermediate. One strategy to overcome with these issues is to use of titanium disulfide (TiS2) as an additive to sulfur electrodes as it is a good electrical conductor and electrochemically active and also has the ability to adsorb polysulfide.

Herein, we investigated TiS2 as additive with sulfur using hierarchical architectures of carbon as effective hosts for S/TiS2. By a facile one-step melting diffusion method, we synthesized S/TiS2@carbon nanofibers (CNFs) composites in which TiS2 was uniformly distributed over the S-CNFs. The hierarchical S/TiS2@CNFs (TiS2, 20 wt%) electrodes shows good initial discharge capacity of 1085 mAh g−1 at 0.05 C rate with high mass loading of material (~6-6.5 mg/cm2 of composite) and ~99% initial coulombic efficiency. The composite electrode shows stable cycling performance for more than 100 charge-discharge cycles with specific capacity of ~750 mAh g-1 at a rate of C/3 and coulombic efficiency over 99%. Thus, in the presence of TiS2 additive, long cycle life and improved sulfur utilization of Li-S cells under high current rate (C/3) are demonstrated with high sulfur mass-loading.
Two Dimensional SiOx Materials As High Capacity Anode Materials for Lithium Ion Battery
Authors: Youn Donghan , Kim Soohwan , Yoo Hyundong , Kim Hansu
Published: February 2020

Si is one of the promising material for Li-ion batteries because of its high theoretical capacity (3,580 mAhg-1). However, Silicon is suffering from drastic cycle fading originated from its severe volume changes during cycling. In this presentation, two dimensional (2D)-SiOx materials prepared by solution evaporation induced interfacial sol-gel reaction method were investigated as high capacity anode materials for lithium ion batteries. The resulting 2D-SiOx showed excellent cycle performance with reversible capacity of 650 mAhg-1, and good rate capability even at a high current density of 50 C (50 A g-1). More detailed electrochemical analysis and material characterizations on the 2D-SiOx materials will be discussed in this presentation.
Bipolar All-Solid-State Battery Enabled By a Perovskite-Based Hybrid Solid Electrolyte
Authors: Shin Hyun-Seop , Park Min-Sik , Jung Kyu-Nam , Lee Jong-Won
Published: February 2020

The increasing number of fire/explosion incidents related to lithium-ion batteries (LIBs) for mobile devices and electric vehicles (EVs) in the recent years have raised significant concerns regarding their safety and reliability. The use of solid electrolytes provides a technical solution to address the safety issues of lithium-ion batteries and enables a bipolar design of high-voltage and high-energy battery modules. The bipolar design avoids unnecessary components and parts for packaging and electrical connection; therefore, it facilitates an increase in the volumetric energy density of the battery, while enabling easy build-up of total output voltage.

Here, we report the design and construction of a multi-layered bipolar ASSB using a hybrid solid electrolyte (HSE) membrane. The HSE membrane proposed in this work consists of inorganic Li0.29La0.57TiO3 (LLTO) perovskite and poly(ethylene oxide) (PEO). The perovskite-structured LLTO was selected as an inorganic solid electrolyte specifically as a result of its high Li+ conductivity, excellent mechanical strength, and high chemical stability against moisture. The hybridization of LLTO with PEO allows for the fabrication of thin and large-area electrolyte membranes with high ionic conductivity, without the need for high-temperature sintering. Moreover, the soft and adhesive PEO improves the interfacial contact between the electrolyte and electrode, resulting therefore in enhanced electrochemical performance of the prepared ASSBs. Although the concept of hybridization between inorganic material (garnet-Li7La3Zr2O12 and NASICON-Li1.5Al0.5Ge1.5(PO4)3) and polymer has been proposed previously, the focus in these earlier studies has been predominantly on optimizing the electrolytes to improve their Li+-conducting and/or mechanical properties and/or demonstrating their applications in the monopolar-type, small-sized ASSB. By contrast, little attention has been given to the design and fabrication of bipolar ASSBs with HSEs, which is essential for demonstrating the feasibility of HSEs in large-scale ASSBs with high voltage and energy. In this study, the HSE membranes based on LLTO and PEO were synthesized in the form of flexible and freestanding sheets with a thickness of ~30 mm using a simple casting method. The optimized HSE membrane exhibits remarkably enhanced Li+ conductivity, electrochemical window, and thermal stability when compared to a solid PEO-only membrane, facilitating reversible charge–discharge operations of ASSBs. Finally, a proof-of-concept bipolar ASSB comprising three unit cells connected in series was designed and constructed using the HSE membrane, and its electrochemical performance was investigated.
High Energy Density Li-Air Battery with the Polymer Electrolyte Coated CNTs Electrode Via Layer-By-Layer Method
Authors: Lee Hyunpyo , Lee Dong Joon , Kim Mokwon , Kim Hyunjin , Kwon Hyuk Jae , Lee Heung Chan , Im Dongmin
Published: February 2020

The Li-air battery has attracted attention for several decades due to its high theoretical energy density (> 3400 Wh/kg). However, it has not been clearly demonstrated that the actual volumetric and gravimetric energy densities are higher than those of Li-ion batteries. In previous studies, generally quite a large amount of electrolyte was employed in preparing the Li-air cells. Usually the electrolyte was much heavier than the carbon materials in the cathode, which made the practical energy density of Li-air battery lower than that of Li-ion batteries. Therefore, the air cathodes with significantly lower amount of electrolyte need to be developed to achieve high specific energy density in Li-air batteries.

In this study, we propose a core-shell structured cathode material with a gel-polymer electrolyte layer covering the carbon nanotubes (CNT). The CNTs were synthesized via a floating catalyst chemical vapor deposition (FCCVD) method. The polymeric layer corresponding to the shell was prepared by a Layer-by-Layer (LbL) coating method utilizing Li-Nafion and PDDA-Cl (poly(diallyldimethylammonium chloride)) together. Several bi-layers of Li-Nafion and PDDA on the CNTs surface were successfully prepared and characterized with XPS, FT-IR, and TGA. The porous structure of the CNTs was found to remain after LbL process, which was confirmed by a nitrogen adsorption/desorption profile and BJH pore size distribution analysis. The porous structure could act as the oxygen channels facilitating the transport of oxygen molecules to react with Li ions on cathode surface. These polymeric bi-layers could provide Li ion pathway after absorbing a small amount of ionic liquid electrolyte, 0.5M LiTFSI EMI-TFSI (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide). Compared with typical cathode where only liquid electrolytes were employed, the total amount of electrolyte in the cathode could be significantly reduced, thus the overall cell energy density could be increased. A Li-air battery with this core-shell structured cathode exhibited a high energy density, ~390 Wh/kg, which was assessed by directly weighing all cell components together including GDL (gas diffusion layer), an interlayer (a separator containing a mixture of LiTFSI, 1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR-14) and PDDA-TFSI), lithium anode and LbL-CNTs cathode. The cycle life of an LbL-CNTs based cathode was found to be 31 cycles, which was not an excellent performance, but nearly twice better than that of CNTs cathode without polymer coats.

Figure 1
High-Throughput Electrochemical Conversion of Gaseous CO2 to C≥2 Products By Fine-Tuning Structure of La2-XSrxCuO4±δ electrocatalyst
Authors: Kolla Praveen , Sun Qiang , Wang Wang , Mukerjee Sanjeev
Published: February 2020

Among other metal catalysts, Copper (Cu) is a well-known for electrochemical reduction of CO2 and its selectivity primarily governed by the applied electrode potential and yields a wide-range of gaseous and liquid products. Specifically, CO2 electroreduction to formic acid, carbon monoxide (CO) and methane were observed at low-potentials <-1.0 V RHE (1), whereas ethylene, ethanol and n-propanol were yielded at high-potentials >-1.0 V RHE (2). On the other hand, catalytic activity of Cu inherently contributes from mixed oxidation states, surface roughness and aspect ratio of nanostructures. Consequently, different strategies such as oxide-derived, mixed metal-oxides, electrooxidized or anodized Cu-surfaces have been investigated to tune its catalytic activity. In addition, Cu-surfaces of different morphologies - spikes, steps and edges, or its nanostructures having different shapes and dimensionality were thoroughly investigated. However, electrochemical performance of Cu-electrocatalysts eventually declines as surface morphology fades out and/or while Cun+ quickly retains its pure metallic-state during long-term electrolysis under electrochemical reduction potentials (3). Moreover, due to limited CO2 solubility in aqueous electrolytes and inability of Cu for direct-activation of gaseous-reactant (CO2(g)), these catalysts displayed low-throughputs (<30 mA/cm2).

In this context, our research demonstrates how Cu-based perovskite-oxides of A2BO4-type, with Cu on B-site, are crucial for electrochemical CO2 reduction and its product selectivity. This presentation sheds light on how these catalysts are unique for fine-tuning Cu-oxidation state with control of lanthanum-elements (on A-site) and/or its partial doping with element of slightly different oxidation-number. This work specifically provides synthetic means of optimizing Cu-structure by relative-doping (x) in La2-xSrxCuO4±δ along with identification/preservation of responsible active-site and depicts the underlaying mechanistic aspects of CO2-electroreduction towards ethanol, n-propanol, and ethylene. The presentation also highlights how the overall oxygen deficient-sites (δ) created within the structure of A2BO4±δ are not only critical for direct activation of gaseous CO2, but also promote throughputs (up to 100-200 mA/cm2) required for commercial implementation.

References:

M. Gattrell, N. Gupta and A. Co, Journal of Electroanalytical Chemistry, 594, 1 (2006).

D. Ren, Y. Deng, A. D. Handoko, C. S. Chen, S. Malkhandi and B. S. Yeo, ACS Catalysis, 5, 2814 (2015).

C. W. Li and M. W. Kanan, Journal of the American Chemical Society, 134, 7231 (2012).
Operando Spectroelectrochemistry Approaches for Aqueous CO2 Reduction
Authors: Jiang Kun , Bell Alexis T.
Published: February 2020

In facing global energy and environmental concerns, developing alternative energy technologies to reduce carbon emission from fossil fuels is of central interest over the years. Herein I’ll briefly summarize some of our previous work on selective CO2 reduction with water into chemical fuels. Targeted for more energy- and cost-effective electrocatalyst design, complementary in situ spectroelectrochemical techniques, including surface enhanced infrared absorption (ATR-SEIRAS), Raman scattering, X-ray absorption and differential electrochemical mass spectroscopies (DEMS), have been developed to shed light on the electrode structure and interfacial species evolution during CO2 reduction. As a result, novel electrocatalytic materials with tunable electronic structure and coordination environment have been demonstrated, as well as their deployment in module energy systems as artificial leaf.
Hierarchically Structured Photoelectrodes Utilizing a Protected Transparent Conducting Oxide Grown Via Atomic Layer Deposition
Authors: Reed Peter Justin , Norman Mya , Coridan Robert
Published: February 2020

Hierarchically structured materials are often used to improve light absorption and photocarrier collection in thin-film photoelectrodes. However, the structures require a continuous conductive coating to function as an electrode and maintain electrical contact to the entire, tortuous surface while being transparent to visible light to minimize parasitic absorption. The electrochemically robust transparent conducting oxide (TCO) fluorine-doped tin oxide (FTO) can only be grown by line-of-sight physical deposition methods such as RF sputtering or spray pyrolysis, which in general prevents the deposition of uniform thin coatings of FTO on the interior of a hierarchichally structured scaffold. Other TCOs (tin-doped indium oxide (ITO), aluminum-doped zinc oxide (AZO)) can be grown conformally by surface specific methods such as atomic layer deposition (ALD), but are only stable at near-neutral pH, limiting their use in photoelectrochemical energy conversion. Here, we describe a strategy for improving the stability of ALD-deposited AZO films for anodic and cathodic operation in alkaline and acidic electrolytes. The addition of a conformal, nanoscale TiO2 coating preserves a conductive AZO film for more than 24 hours at pH > 13. This is an improvement of several orders of magnitude compared to the lifetime of pure AZO films, which is also observed in acidic (pH < 1) environments. Although the TiO2 coating is not significantly conductive alone, we observed no decrease in the conductivity of the layered AZO/TiO2 film. The TiO2-coated AZO film was used as an electron collector on hierarchically porous scaffolds formed from close-packed inorganic silica spheres. The improved electrochemical stability will be utilized in the construction of ultra-thin film photoelectrodes in hierarchichally-structured systems with earth-abundant semiconductors, such as cupric oxide (CuO) or hematite (α-Fe2O3).
(Invited) Precise Structure Control Enabling Efficient Water Splitting for Hydrogen Generation
Authors: Li Jiangtian , Chu Deryn
Published: February 2020

Hydrogen is a clean and high-density energy source. Electrochemically splitting water to generate hydrogen offers a renewable and sustainable approach with the electric energy input properly from the Sun and the wind. The sluggish kinetics is the main obstacle for OER and HER, which regularly results in a large overpotential for overall water splitting. Active electrochemical catalysts are essential to initiate chemical reactions with small overpotentials and speed up the reaction rate. In this presentation, we will show our recent research studies on nanostructured chalcogenides and oxides as efficient catalysts for water splitting by engineering the exposed facets, core-shell, and architectural composites. Theoretical prediction and experimental methodology are developed to coordinate the reaction kinetics like the water dissociation and H adsorption/desorption with the inter/surface/electronic structures of the catalyst. This provides insights toward fundamental understanding on the reaction mechanism and better design concepts for catalysts.
(Invited) Heterogeneous Doping, a Novel in-Situ Synthesis of Supported Metal Nanocatalysts
Authors: Jung WooChul
Published: February 2020

Supported metal nanoparticles hold great promise for many fields, including catalysis and renewable energy. Here we report a novel methodology for the in-situ growth of architecturally tailored, regenerative metal nanocatalysts that is applicable to a wide range of materials. The main idea underlying this strategy is to selectively diffuse catalytically active metals along the grain boundaries of host oxides and then to reduce the diffused metallic species to form nanoclusters. As a case study, we choose ceria and zirconia, the most recognized oxide supports, and spontaneously form various metal particles (Ni, Co, Cu, Au, and Pt) on their surface with controlled size and distribution. Metal atoms move back and forth between the interior (as cations) and the exterior (as clusters) of the host oxide lattice as the reductive and oxidative atmospheres repeat, even at temperatures below 700°C. Furthermore, they exhibit excellent sintering/coking resistance and reactivity toward CO chemical oxidation and H2 electrochemical oxidation, demonstrating potential to be used in various applications.
Defect Engineering of NiCo2(O, S)x/S-CNTs Oxygen Electrocatalysts for Rechargeable Quasi-Solid-State Flow Zinc–Air Batteries
Authors: Xu Nengneng , Su Tianshun , Richard Kayla N. , Wang Yudong , Zhou Xiao-Dong , Qiao Jinli
Published: February 2020

Rechargeable zinc-air batteries have renewed interest in advanced clean energy-storage technologies, due to its high energy density, eco-friendliness, and low cost. The challenge to commercialize Zn-Air batteries is to design highly efficient bifunctional oxygen catalysts for oxygen reduction and evolution reactions (ORR and OER). Among the various non-precious metal oxides, spinel and perovskite oxides have been considered as potential bifunctional oxygen catalysts owing to their good stability and chemical versatility in alkaline conditions (KOH). However, cation segregation and phase precipitation at the surface limit the activity and stability of these oxides. As a result, it is necessary to improve oxygen catalysis by engineering the anion chemistry of metal oxides. Sulfur (S) as chalcogens is expected to alter the chemical properties as well as electronic structures of metal oxides by substituting partial oxygen, which induces distorted structures and oxygen defects. In this work, a novel bifunctional catalyst of ultra-small NiCo2(O, S)x particles with S doped carbon nanotubes (NiCo2(O, S)x/S-CNTs) is synthesized. A composite of NiCo2(O, S)x/S-CNTs shows high oxygen electroactivity (a low over-potential of 0.78 V) and long-term stability toward ORR and OER. Particularly, the quasi-solid-state flow zinc-air batteries constructed by this hybrid catalyst displays a high power density of 450 mWcm-2 and long-term charge-discharge cycle durability for more than 860 hours with a small charge/discharge voltage gap of 0.75 V at 10 mA cm-2 under ambient conditions.
In Situ Exsolved Co Nanoparticles on Ruddlesden-Popper Material As Highly Active Catalyst for CO2 Electrolysis to CO
Authors: Park Seongmin , Kim Yoongon , Han Hyunsu , Chung Yong Sik , Yoon Wongeun , Choi Junil , Kim Won Bae
Published: February 2020

Herein, we report a highly active Ruddlesden-Popper material with a mechanism of in situ exsolution of Co nanoparticles and its use as an effective catalyst for CO2 reduction to produce CO in a solid oxide electrolysis cell. This catalyst is simply prepared by transforming a perovskite of La0.6Sr0.4Co0.7Mn0.3O3 and revealed a good reversibility of structural transition between the Ruddlesden-Popper and the perovskite structure during reaction cycles. A very high current density of 630 mA/cm2 can be accomplished at a voltage of 1.3 V and temperature of 850 °C with a very high Faraday efficiency of 95% or larger. More importantly, no sign of degradation is indicated as observed by galvanostatic stability test, implying that this Ruddlesden-Popper structure is highly robust as the cathode catalyst for the CO2 electrolysis. CO2-TPD result shows that the exsolved Co metal nanoparticles on the ceramic support increased the adsorption capacity for CO2 molecules with a high degree of stability. Also, TGA and XANES results confirm that the Ruddlesden-Popper support possessed the oxygen vacancy contents which could contribute to an increase of the catalytic activity. As a result, in situ exsolved Co nanoparticles and high concentration of oxygen vacancies caused by the structural transition are responsible for its high stability and catalytic activity.
Enhancement of Electrochemical Properties of Anode-Supported Solid Oxide Fuel Cells using In-situ Synthesis of Multi-doped Ceria Nanoparticles
Authors: Hong Jong-Eun , Ahmad Ishfaq Hafiz , Lim Tak-Hyoung , Lee Seung-Bok , Park Seok-Joo , Song Rak-Hyun , Lee Kang Taek
Published: February 2020

Nano-size Sm and Nd-doped ceria (SNDC) that has the higher ionic conductivity than that of Gd-doped ceria (GDC) was applied to a commercial cathode of solid oxide fuel cells by using an infiltration process in order to improve electrochemical performance and durability. SNDC nano-particles were synthesized via an in situ sol–gel process on Sr- and Fe-doped LaCoO3 (LSCF) and GDC composite cathode. The microstructure and electrochemical property of the tailored cathode to oxygen reduction reaction were evaluated. It appeared that the application of the SNDC infiltrated cathode decreased the electrode polarization resistance and thus increased the power density, which was attributed for the conductive nanoparticles to expand the reactive sites and promote the cathode reaction.
Novel Synthesis of Mn-Ni-Co Oxide(MNCO)@g-C3N4 Ternary Ribbon-like Hetero Nanocomposite for Psuedocapacitor Applications
Authors: Mawari Nemi Chand , Meher Sumanta Kumar
Published: February 2020

Since last few years, the hassle of clean, efficient, and renewable energy sources is remarkable and thereby driving intense scientific concern in the production, storage and management of this precious energy. Among variety of electrical energy storage devices, supercapacitors (SCs), also known as electrochemical capacitors, have industrial attention because of their high power density and very long cyclic stability as compared to their counterparts such as batteries, fuel cells and conventional capacitors etc.

To improve the electrochemical properties of the electrode materials, Mn-Ni-Co-Oxide(MNCO)@g-C3N4 Ribbon-like Hetero-nanoarrays were synthesized by a simple two-step approach including hydrothermal method and subsequent calcination process. This ternary metal oxide composite was directly utilized for the psuedocapacitive investigation because it is believed that these three metal elements can provide synergistic effects during the redox reaction process compared to the single component metal oxides. Due to similar atom radii of the elements, Mn-Ni-Co ternary oxide (MNCO)@g-C3N4 without crystal structure change has been identified as one kind of the most attractive supercapacitive electrode materials.

The chemical composition and morphology of the material was characterized by XRD, EDS and FESEM and HRTEM techniques. The electrochemical capacitance of MNCO@g-C3N4 was examined by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance measurements. Results shows that the MNCO@g-C3N4 electrode material exhibits electrochemical activity for supercapacitor applications. A maximum specific capacitance value of 5624 F g-1 could be obtained under an applied current density of 1 Ag-1 in 6 mol L-1 KOH electrolyte. It is envisaged that the novel MNCO@g-C3N4 ternary oxide composite material can be an alternate electrode material for high-performance supercapacitor application.
The Mechanism of Electrochemical Oxidation of Sulphite on Gold Nanoparticles
Authors: Cai Xiaosheng , Foord John S. , Compton Richard G
Published: February 2020

The electrooxidation of sulphite has been studied in acid solution on a boron doped diamond electrode modified by gold nanoparticles. The Au nanoparticles are deposited by pulse deposition which involves nucleation and growth steps. The morphology evolves from sphere to dendrite with the increasing of growth time. Simultaneously the interparticle distance decreases leading to the high overlapping of diffusion layer of each Au particle and therefore the formation of a linear planar diffusion. The voltammetry for sulphite oxidation shows the dependence of the square root of scan rates and concentrations. When the concentration is decreased, the current of reverse reduction peak emerges, suggesting an EC2 mechanism (a one-electron transfer process followed by a dimerization chemical reaction). The digital simulation fits the experimental voltammograms well, further confirming the proposed mechanism.
(Invited) Brief Historical Overview and Current Status of Electrochemical Neurotransmitter Detection
Authors: Shadlaghani Arash , Farzaneh Mahsa , Kinser Dacen , Reid Russell C.
Published: February 2020

Abnormal neurotransmitter concentrations are associated with serious disorders including traumatic brain injury, Parkinson’s and Alzheimer’s diseases, epilepsy, and chronic pain. Understanding the causes and potential cures of these disorders requires highly selective, sensitive, and responsive neurotransmitter detection. From its inception in the early 1970s, electrochemical neurotransmitter detection has become a vibrant research field that is addressing the need for sensitive, real-time quantitative neurotransmitter analysis. Electrochemical techniques can detect both electroactive and nonelectroactive species but different materials and methods are used depending on how easily the species of interest can be electrolyzed and distinguished from other analytes. Electrode materials and design have evolved from being macroscale devices for sensing one analyte at a single electrode to the point that there now exist microscale electrode arrays, some of which are capable of simultaneously monitoring multiple neurotransmitters. In addition, some electrode arrays are flexible in order to more amenably be integrated into soft, living tissue for real-time in vivo monitoring. After a brief historical overview, this presentation summarizes the current state of electrochemical neurotransmitter detection by highlighting notable examples, applications, challenges and future directions.

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Hot Holes Assist Plasmonic Nanoelectrode Dissolution
Authors: Al-Zubeidi Alexander , Hoener Benjamin S , Collins Sean Stevenson Edward , Wang Wenxiao , Kirchner Silke , Hosseini Jebeli Seyyed Ali , Joplin Anneli , Chang Wei-Shun , Link Stephan , Landes Christy F
Published: February 2020

Strong light absorbing properties, and the ability to drive electrochemical reactions on their surface has sparked, allow plasmonic metal nanoparticles to serve as photocatalysts. After plasmon excitation, hot charge carriers are generated in the metal nanoelectrode, driving electrochemical reactions. To achieve plasmonic photocatalysis, the hot charge carriers must be harnessed before they decay by giving off heat to the surroundings. Here, we demonstrate the role of photogenerated hot holes in oxidative electrodissolution of individual gold nanorods in chloride electrolyte. We monitor the plasmon resonance spectroscopically using snapshot hyperspectral imaging with millisecond time resolution, while electrochemically tuning charge carrier density. We show that light induced hot charge carriers enhance the rate of gold oxidation and subsequent electrodissolution tenfold. Importantly, we find that hot holes generated from interband transitions compared to holes in the sp-band around the Fermi level contribute to electro-oxidation. We further show that the reaction onset potential cannot be lowered below the chloride onset potential, demonstrating that electrochemical mediation is required. These results provide new insights into hot hole driven photocatalysis while emphasizing the need for statistical descriptions of electrochemical non-equilibrium processes on innately heterogeneous nanoparticle supports.

Figure: Schematic representation of experimental setup and mechanism. a: when positive potentials are applied while illuminating the nanoparticle, the scattering intensity and hence volume of the nanoparticle decreases (see inset). b: photo-generated hot holes inject into the HOMO of adsorbed chloride.

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Study of the Electrochemical Mechanism of Dyes in Ionic Liquid By NIR Spectroelectrochemistry
Authors: Fanjul Pablo , Ibáñez David , Junquera-Pérez Alejandro , González-García María Begoña , Hernández-Santos David
Published: February 2020

Over the last years, near infrared (NIR) spectroscopy has received growing attention because it is a fast, non-destructive and non-invasive technique. In order to provide vibrational information of different systems, NIR spectroscopy is an interesting alternative rather than other techniques. However, it is well-known the aqueous limitation in NIR spectroscopy due to the high absorbance of water in this spectral range.

In this work, a new methodology based on ionic liquids is proposed to overcome the water restriction. Ionic liquids are an interesting alternative because they show excellent properties such as wide electrochemical potential window, good ionic conductivity and high thermal stability, and also, they do not display aqueous contribution.

As result of the combination of NIR spectroscopy and electrochemistry in a novel instrument, the simultaneous acquisition of information of different nature in a unique experiment allows monitoring different processes that take place on the electrode surface. As proof of concept, the electrochemical behavior of two dyes (crystal violet and malachite green) with similar chemical structure have been studied by NIR spectroelectrochemistry. They show different electrochemical response as well as different NIR spectra: crystal violet requires more positive potentials to be oxidized and its NIR spectrum displays 2 bands at 1000 and 1200 nm, while malachite green is oxidized at lower potential and only shows one NIR band at 1255 nm. Combination of electrochemistry and NIR spectroscopy allows to understand the electrochemical mechanism of both dyes. In this way, NIR spectroelectrochemistry opens new gates not only for qualitative purposes but also for quantitative applications as for example for the resolution of mixtures.