bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Visible Light Absorbing Materials for Solar Fuels, Ga(Sbx)N1-X
Authors: Sunkara Swathi , Vendra Venkat Kumar , Jasinski Jacek B , Deutsch Todd G , Menon Madhu , Rajan Krishna , Sunkara Mahendra Kumar 
Published: February 2020

In this work large band gap bowing of dilute antimonide alloys of gallium nitride, Ga(Sbx)N1-x has been investigated. Our computational calculations using first principles density functional theory2 revealed that a small amount of Sb incorporation is sufficient to achieve a significant band gap reduction in GaN from 3.4eV to 2eV. Theoretical calculations predicted that Ga(Sb)xN1-x alloys with 2 eV band gap straddle the electrochemical potentials of the hydrogen and oxygen evolution reactions. Theoretical computations with Sb composition beyond 7% change the electronic band gap from direct to indirect.
Synthesis of crystalline GaSbxN1-x alloys were carried out using metal organic chemical vapor deposition using trimethyl gallium (TMGa) and Trimethyl Antimony (TMSb) and ammonia at x values ranging from 0-8%. Synthesis was carried out on different planar substrates and GaN nanowires. X-ray diffraction measurements showed a monotonic increase in the lattice with increase in antimonide composition which corroborates with theoretical calculations. Optical measurements like UV-Vis spectroscopy and photocurrent spectroscopy suggested a rapid decrease in band gap from 3.4 to 2 eV with small concentration of antimonide incorporation. Experimental data from optical measurements indicated direct band gap transition for alloys less than 7at% and an indirect band gap transition for alloys beyond 7% as shown in fig. 1. In addition Mott Schottky measurements showed that Ga(Sb)xN1-x alloys ranging from 0-8% straddle the water oxidation and reduction potentials in agreement to computational calculations. Moreover, the photo-electrochemical data on activity and stability suggest that these alloys are highly suitable for solar water splitting under visible light irradiation.

Fig. 1 Tauc plots for direct transition and indirect transition for 2 % Sb (a,b) and 8 % Sb (c,d).

Acknowledgements: Financial support from US Department of Energy (DE-FG02-07ER46375) and NSF (DMS1125909).

References:

1. S. Sunkara, V. Vendra, J. Jasinski, T. Deutsch, A.N. Andriotis, K. Rajan, M. Menon and M.K. Sunkara, “New Visible Light Absorbing Materials for Solar Fuels, Ga(Sbx)N1-x”, In Review (2013)
2. R.M. Sheetz, E. Richter, A.N. Andriotis, C. Pendyala, M.K. Sunkara and M. Menon, “Visible light absorption and large band gap bowing in dilute alloys of gallium nitride with antimony”, Phys. Rev. B, 84, 075304 (2011)
Solar Fuel Generation By Semiconductor-Graphene Heterogeneous Photocatalysts
Authors: Wu Nick , Meng Fanke 
Published: February 2020

Semiconductors have been extensively used as photocatalysts and photoelectrodes for solar fuel generation. Currently single semiconducting material cannot suffer from low efficiency of conversion of solar energy to chemical energy. An alternative to overcome this barrier is to the development of hetero-structured photocatalysts.
This presentation shows that integration of semiconductors with graphene can significantly improve the photocatalytic activity. First, hematite (a-Fe2O3) nanocrystals have been deposited on the reduced graphene oxide (rGO) sheets to form the hematite/rGO heterogeneous photocatalyst, which shows much higher photocatalytic activity toward water oxidation.1 The photocatalysis enhancement is due to the fact that facilitates the charge migration and reduces the charge recombination rate.
In addition, we have developed a heterogeneous photocatalyst based on the nanoscale p-n junction of p-type molybdenum disulfide/n-type nitrogen-doped reduced graphene oxide.2 It is interesting that MoS2 alone exhibits negligible photocatalytic activity. In contrast, the MoS2/rGO p-n junction photocatalyst show significant photocatalytic activity toward hydrogen generation.

References

[1] F. Meng, J. Li, S. K. Cushing, J. Bright, M. Zhi, J. Rowley, Z. Hong, A. Manivannan, A. D. Bristow, N. Q. Wu, ACS Catalysis, 3 (2013), 746–751.
[2] F. Meng, J. Li, S. K. Cushing, M. Zhi, N. Q. Wu, J. Am. Chem. Soc., 135 (2013), 10286-10289

Acknowledgement:

The resource and facilities used were partially supported by NSF (EPS 1003907), the West Virginia University Research Corporation and the West Virginia EPSCoR Office. The use of WVU Shared Facility was appreciated.
Water Oxidation and CO2 Reduction Catalyst for Artificial Photosynthesis
Authors: Jia Hongfei , McDonald Kenneth J , Gower Mitchell , Zhou Li Qin , Ling Chen 
Published: February 2020

Photocatalytic or photoelectrochemical processes that couple water oxidation and CO2 reduction are currently under intense investigation for solar fuel production. As these so called “artificial photosynthesis (AP)” systems are expected to remediate the issue of ever increasing CO2 level in the atmosphere, it is necessary to construct them using cheap and efficient materials for large scale deployment. The importance of water oxidation and CO2 reduction catalysis for AP has been well recognized in recent years, yet significant challenges still remain to find low cost materials that are both efficient and stable [1]. Towards the search for catalyst based on earth abundant materials, we previously investigated transition metal tungstates as water oxidation catalysts [2] and nickel macrocycles for CO2 reduction [3]. In this work, perovskites-type of metal oxides is further studied to improve catalyst performance at neutral pH as oxygen evolution catalyst. We also report a new strategy of ligand modification to silver surface, which allows the control of product selectivity for electrochemical CO2 reduction. Details about materials synthesis, characterization of physiochemical properties and evaluation of catalytic performance will be discussed in this presentation, as well as studies on catalyst stability and the influences of electrolytes.
(1) J. R. McKone, N. S. Lewis and H. B. Gray, Chem. Mater., 2013 ASAP
(2) H. Jia, J. Stark, L. Q. Zhou, C. Ling, T. Sekito, Z. Markin. RSC Adv. 2012, 2(29), 10874-10881
(3) J. Schneider, H. Jia, K. Kobiro, et al. Energy Environ. Sci. 2012, 5, 9502-9510.
Gas Cross-over and Durability of Membrane Electrode Assemblies
Authors: Büchi Felix N. , Kreitmeier Stefan 
Published: February 2020

Durability of the membrane electrolyte is a key factor for the longevity of polymer electrolyte fuel cells. A loss of gas separation is the most detrimental failure mode of perfluorosulfonic acid membranes. Mechanical formation of micron sized membrane defects is the main degradation process during fuel cell operation. This process is accelerated by variations in the operating conditions, such as humidity and temperature, and by imperfections and local defects of the gas diffusion electrodes.
The impact of these local defects, termed pinholes is studied by implementing artificial micron sized defects in the membrane by focused ion beam (FIB) milling. Such membranes were then operated in different accelerated stress tests to study the development of chemical, mechanical and thermal degradation processes. Degradation at membrane defects was investigated post mortem using synchrotron based X-ray tomographic microscopy (XTM) and FTIR spectro-microscopy (see Figure 1) [1]. Gas cross-over, a key function for degradation, is controlled by operating conditions and material characteristics and was measured in-situ by mass spectrometry using a tracer gas concept [2, 3].
From the results an overall degradation mechanism at membrane defects can be thus formulated [4].
[1] S. Kreitmeier, M. Michiardi, A. Wokaun, F. N. Büchi, Factors determining the gas crossover through pinholes in polymer electrolyte fuel cell membranes, Electrochim. Acta, 80, 240-247 (2012)
[2] G. A. Schuler, A. Wokaun, F. N. Büchi, Local online gas analysis in PEFC using tracer gas concepts, J. Power Sources, 195, 1647–1656 (2010)
[3] S. Kreitmeier, G. A. Schuler, A. Wokaun, F. N. Büchi, Investigation of membrane degradation in polymer electrolyte fuel cells using local gas permeation analysis, J. Power Sources, 212, 139-147(2012)
[4] S. Kreitmeier, P. Lerch, A. Wokaun, F.N. Büchi, Local degradation at membrane defects in polymer electrolyte fuel cells, J. Electrochem. Soc. 160, F456-F463 (2013)
The Graphitization-Stability Relation of High Surface Area Carbons
Authors: Stamatin Serban Nicolae , Nørgaard Casper Frydendal , Andersen Shuang Ma , Skou Eivind Morten 
Published: February 2020

Fuel cells have benefited from increasing attention for the last two decades. They have shown their ability of producing both electrical energy and heat with high efficiency and low environmental pollution. One of the main challenges which need to be addressed before commercialization is the durability and activity of the membrane-electrode assembly (MEA). This is formed of proton exchange membrane sandwiched between two catalytic systems. The catalyst in form of 2-3 nm particles is supported on a high surface area active carbon. The most used catalyst is Pt and its alloys which carry a large contribution to the total cost associated with a fuel cell [1]. However, Pt activity is lost during fuel cell operation due to the contribution of a matrix of phenomenon such as dissolution[2], particle agglomeration, particle detachment, Ostwald ripening and carbon support corrosion[3].
This work focuses on how the overall catalyst durability depends on morphological and chemical properties of the catalyst support material. Morphological and chemical changes have been induced in a high surface area carbon by heat treatment at different temperatures. The resulting samples, along with the pristine material, have been characterized by Raman spectroscopy, XRD and XPS. Furthermore, all these support materials have been platinized and tested for activity in the oxygen reduction reaction as well as their stability under potential cycling in acidic environment The degradation was done according to the FCCJ degradation protocol and took place in a two compartment – three electrode cell setup.
Fig. 1 TG-DSC curve of the initial high surface area carbon

Acknowledgement

This work has been supported by the Danish PEMFC Catalysts for Boosted Activity and Enhanced Durability (Energinet. dk project no. 2011-1-10669).

References

[1] H. A. Gasteiger, D. R. Baker, R. N. C. Hydrogen Fuel Cells: Fundamentals and Applications; Wiley: Copenhagen, 2010
[2] Topalov, A.; Katsounaros, I.; Auinger, M.; Cherevko, S.; Meier, J. C.; Klemm, S. O.; Mayrhofer, K. J. J. Angewandte Chemie (International ed. in English) 2012, 51, 12613–5.
[3] Meier, J. C.; Galeano, C.; Katsounaros, I.; Topalov, A. A.; Kostka, A.; Schu, F.; Mayrhofer, K. J. J. ACS Catalysis 2012, 2, 832–843.
Glycosylation of a Novel Sugar Orthoester Under Electrochemical Conditions
Authors: Kawa Kohei , Saitoh Tsuyoshi , Nishiyama Shigeru 
Published: February 2020

Glycosylation is one of the important synthetic methodologies to generate glycoside antibiotics and sugar chains, which tightly interact with living body. A number of condensation methodologies to acquire glycosidic linkages with efficient selectivity and yields, have been developed during the last century, and related investigation is powerfully promoting even today. Among such efforts, electrochemical procedure for oxidation-potential differentiation of anomeric substituents, has been exploited by Yoshida et al. to generate oxocarbenium cation intermediates.
We present another electrochemical glycosylation by using an extremely stable sugar orthoester derivative, which is intact under standard work-up and chromatographic conditions. Thus, the orthoester, prepared by the standard Koenig Knorr reaction of the corresponding glucose tetra-O-benzoyl bromide, was reacted with the 6-hydroxyl glucoside in the presence of EGA (electrochemically generated acid) to give the desired b-glycoside in 90% yield. EGA was produced by anodic oxidation of cyclohexanol under CCE conditions (6 mA, 3 F/mol, supporting salt Bu4NClO4 in (ClCH2)2, divided cell, anode: GC plate, cathode: Pt wire). Detailed synthetic process will be discussed.
The Addition of ArSSAr to Alkenes: The Implications of a Cationic Chain Mechanism Initiated by Electrogenerated ArS(ArSSAr)+
Authors: Matsumoto Kouichi , Sanada Tomonari , Shimazaki Hayato , Shimada Kazuaki , Hagiwara Shino , Fujie Shunsuke , Ashikari Yosuke , Suga Seiji , Kashimura Shigenori , Yoshida Jun-ichi 
Published: February 2020

Organosulfur compounds have received much attention because they serve as useful building blocks in organic synthesis and exhibit interesting physical properties in materials chemistry. To synthesize such compounds, the addition of ArSSAr to carbon-carbon multiple bonds is one of the most efficient methods.
We have recently reported the reactions of alkenes with a stoichiometric amount of ArS(ArSSAr)+, which is generated by electrochemical oxidation and accumulated as a cation pool of ArSSAr.1) Thiiranium ions are generated as initial intermediates. Quenching with hard nucleophiles such as MeOH and H2O leads to the addition of an ArS group and RO group (R = Me or H) across the carbon-carbon double bond. In contrast, the use of soft nucleophiles such as ketene silyl acetals, allylsilanes, and Et3N leads to the addition of two ArS groups across the carbon-carbon double bond. Presumably, soft nucleophiles assist nucleophilic attack of ArSSAr on the thiiranium ion intermediate. We envisioned that the addition reaction of ArSSAr to alkenes may proceed with a catalytic amount of ArS(ArSSAr)+ if another molecule of ArSSAr plays a role of a soft nucleophile. This is indeed the case, if we use Bu4NB(C6F5)4 as a supporting electrolyte, and herein, we report this chemistry (Scheme 1).2)

We focused on the reaction of ArSSAr (Ar = p-FC6H4) and (E)-β-methylstyrene with a catalytic amount of electrochemically generated ArS(ArSSAr)+ (Ar = p-FC6H4), as a model reaction. The reaction gave the addition product in 78% yield (Scheme 1). The addition took place anti-selectively, which was confirmed by the comparison of the NMR spectra of the product with those reported in the literature.1a) The present reaction seems to proceed by a cation chain mechanism.
In the prsentation, the details of optimization conditions and the scope and limitations of the present reaction will be discussed.

References

1) (a) Fujie, S.; Matsumoto, K.; Suga, S.; Nokami, T.; Yoshida, J. Tetrahedron
2010, 66, 2823-2829. See also, (b) Matsumoto, K.; Suga, S.; Yoshida, J. Org. Biomol. Chem.
2011, 9, 2586-2596.
2) Matsumoto, K.; Sanada, T.; Shimazaki, H.; Shimada, K.; Hagiwara, S.; Fujie, S.; Ashikari, Y.; Suga, S.; Kashimura, S.; Yoshida, J. Asian J. Org. Chem.
2013, 2, 325-329.
Redox Behavior and Reactions of Cobalt Porphycene Derivatives
Authors: Hisaeda Yoshio , Hashimoto Koichi , Saeki Tatsuya , Shimakoshi Hisashi 
Published: February 2020

Tetrapyrrole compounds are very important for the biological system, and these are pigments of life. Heme protein has an iron porphyrin, and chlorophyll contains a magnesium porphyrin derivative. And vitamin B12 has a cobalt corrin. These tetrapyrrole compounds have various functions.1 Inspired by the significance of the porphyrins, a new research direction has emerged that is devoted to the preparation and study of non-porphyrin tetrapyrrolic macrocycles. In this symposium, we will present photochemical and electrochemical reactions of porphycene derivative, which is a porpyrin isomer.
We prepared various brominated porphycenes.2 The singlet oxygen production ability via energy transfer from the triplet state of the porphycene was controlled by the number of bromine. And then, the porphycene having an ionic liquid tag was synthesized and the photo-oxidation reaction in ionic liquid was investigated.3

Tetrapropyl porphycene (H2TPrPc) was synthesized according to the reported procedure.4 A hydrogenated porphycene was obtained by a hydrogenation of H2TPrPc in the presence of zinc and hydrochloric acid.5 Cobalt complexes (cobalt porphycene and cobalt dihydroporphycene) were synthesized by the reaction with [CoII(acac)2] as a metal source. Redox properties were examined by cyclic voltammetry and controlled potential electrolysis. UV-vis spectra of controlled-potential electrolysis revealed that spectra of cobalt porphycene and cobalt dihydroporphycene were quite different in the reduced conditions. These data indicate that the cobalt porphycene was reduced to form a ligand reduced anionradical, but cobalt dihydroporphycene was reduced to form Co(I) species. It suggests the ligand hydrogenation can change the redox behavior.
It is known that cobalt porphyrin can form a Co-C bond by the oxidative addition with Co(I) species and an alkyl halide. Cobalt porphycene is not reduced to form the corresponding Co(I) species unlike cobalt porphyrin. We found that Co-C bond formation is mediated by the reduced ligand of cobalt porphycene. This new reaction, “redox-active ligand-mediated Co-C bond formation of porphycene”, will be reported.

Reference

(1) Hisaeda, Y.; Tahara, K.; Shimakoshi, H.; Masuko, T. Pure Appl. Chem., 2013, 85, 1415.
(2) Shimakoshi, H.; Baba, T.; Iseki, Y.; Aritome, I.; Endo, A.; Adachi, C.; Hisaeda, Y. Chem. Commun., 2008, 2882.
(3) Shimakoshi, H.; Sasaki, K.; Iseki, Y.; Hisaeda Y. J. Porphyrins Phthalocyanines, 2012, 16, 530.
(4) Vogel, E.; Balci, M.; Pramod, K.; Koch, P.; Lex, J.; Ermer, O. Angew. Chem. Int. Ed. Engl., 1987, 26, 928.
(5) Okawara, T.; Hashimoto, K.; Abe, M.; Shimakoshi, H.; Hisaeda, Y. Chem. Commun., 2012, 48, 5413.
Phosphorus: An Alternative for High Capacity Li-Ion Battery Anodes
Authors: Nitta Naoki , Magasinski Alexandre , Yushin Gleb 
Published: February 2020

Greater gravimetric and volumetric electrode capacities could result in battery technologies finding greater use in transportation, industrial equipment, electronics, and electric grid applications. Currently, the volumetric capacities of graphite electrodes used in commercial Li-ion cells approach 500 mAh/cm3, while the volumetric capacities of commercial cathodes approach 700 mAh/cm3. Thus, there is a pressing need to develop high capacity anodes to match or exceed the volumetric capacities of cathodes. Tin (Sn) and silicon (Si) – based anodes have been heavily investigated in recent years, while many other materials have received significantly less attention (1). Phosphorus (P) had attracted very little interest until recent years, perhaps due to its difficulty in handling, but has since been shown to offer high gravimetric capacity and rate capability (2). Furthermore, the theoretical volumetric capacity of P is higher than that of Si (2266 mAh/cm3 for Li3P vs. 2190 mAh/cm3 for Li15Si4) (3,4), and Li3P is known to have high Li+conductivity (5).
Here we report on our early investigations of P-based anodes produced using various polymeric binders. The choice of binder material is key to the development of well performing electrodes (6,7). A broad range of binders were tested and analyzed for their impact on the stability and rate performance of phosphorous-carbon composites. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used to analyze both the structure and chemistry of the anode materials before and after cycling. Atomic force microscopy (AFM) was used to test mechanical properties of polymer binders (such as swelling and stiffness) in electrolyte solvent solution. Cyclic voltammetry (CV) at different rates was used to test both the electrochemical stability of the polymers and performance of P-based anodes, while electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge cycling at different current densities were additionally used to test the electrochemical performance of the final electrodes in half cells. Our results indicate significant promise for P-based anodes in select applications.
REFERENCES

N. Nitta and G. Yushin, Part. Part. Syst. Char., (2013).

J. Qian, D. Qiao, X. Ai, Y. Cao, and H. Yang, Chem. Commun., 48, 8931 (2012).

A. Jain, S.P. Ong, G. Hautier, W. Chen, W.D. Richards, S. Dacek, S. Cholia, D. Gunter, D. Skinner, G. Ceder, K.A. Persson, APL Materials, 1, 01002 (2013).

F. Zhou, M. Cococcioni, C. Marianetti, D. Morgan, G. Ceder, Phys. Rev. B, 70, 235121 (2004).

G. Nazri, Solid State Ionics, 34, 97 (1989).

A. Magasinski, B. Zdyrko, I. Kovalenko, B. Hertzberg, R. Burtovyy, C. F. Huebner, T. F. Fuller, I. Luzinov, and G. Yushin, ACS Appl. Mater. Interfaces, 2, 3004 (2010).

I. Kovalenko, B. Zdyrko, A. Magasinski, B. Hertzberg, Z. Milicev, R. Burtovyy, I. Luzinov, and G. Yushin, Science, 334, 75 (2011).
Highly–stable Ternary Si/Carbon Nanotube/Carbon Nanofiber Anodes for Li-Ion Batteries
Authors: Kim Yong Seok , Joo Yong Lak , Cummins Jamie , Patel Bharat , Chakrapani Srinivasan , Lee Sangho 
Published: February 2020

Despite the highest theoretical capacity, silicon anodes for Li-ion batteries have two critical drawbacks of (i) severe volume expansion leading to electrical disconnection and (ii) formation of poor electronic conductive solid–electrolyte interface caused by deformation of electrolyte at low potential,[1,2
] leading to a poor cycle performance. Herein, we fabricated ternary silicon nanoparticles (Si NPs) /carbon nanotube (CNTs) /carbon nanofibers (CNFs) via water-based electrospinning process, followed by carbonization. Since CNTs provide excellent electrical and electronic properties from their one–dimensional (1–D) feature, they could be easily assembled with Si NPs into nanofibers and improve the charge conductivity and structural stability for our anodes. Furthermore, the carbon nanofibers made from polyvinyl alcohol polymer can make Si NPs connected each other to form networking electrodes. Cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge tests of this ternary anode demonstrated better activity and smaller charge transport resistance than pure SiNPs and our previous Si rich carbon nanofibers[3]. Furthermore, more than two-fold increase in the capacity retention was achieved for the ternary anode compared to that of Si rich carbon nanofibers after 100 cycles. In addition, our ternary anodes exhibited about 1,000 mAh/g even at high charging rates after 150 cycles. This improvement of cycle life should be attributed to facilitating charge transport and distribution of Si NPs by employing 1–D CNTs and carbon nanofibrous networks, and our ternary SiNPs/CNTs/CNFs system provided by scalable water-based spinning should overcome current barriers to commercializing Si-based anodes such as pulverization and low production rate.

References

[1] H. Wu, Y. Cui, Nano Today
2012,
7
, 414.
[2] Wu H.; Chan G.; Choi J. W.; Ryu I.; Yao Y.; McDowell M. T.; Lee S. W.; Jackson A.; Yang Y.; Hu L.; Cui Y. Nature Nanotech.
2012, 7, 310.
[3] Y.S. Kim, K.W. Kim, D. Cho, N.S. Hansen, J. Lee and Y.L. Joo, ChemElectroChem
2013, (in press).