bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epitaxial CaTi5O11 and TiO2-B Thin Films for High Rate Lithium-Ion Batteries
Authors: Pan Xiaoqing 
Published: February 2020

The bronze polymorph of titanium dioxide (TiO2-B) is interesting for many applications including high rate energy storage, solar cells, photocatalysis, thermoelectrics and sensing, owing to its uniquely layered structure and highly asymmetric unit cell. Although known to have advantages over anatase or rutile, high quality bronze phase TiO2-B specimens that demonstrate good electrochemical properties thus far have exclusively been nano-structured powders prepared by hydrothermal methods. We have recently discovered that Ca can stabilize the bronze structure, forming a variant phase CaTi5O11, which has then been successfully synthesized in epitaxial single-crystalline thin films by pulsed laser deposition (PLD), a completely waterless process. Due to the near-perfect lattice match, the CaTi5O11 film can be used as a template layer to grow high quality, water-free TiO2-B films on top, which facilitates the synthesis and application of both materials on a wide variety of substrates, including SrTiO3, Nb:SrTiO3, LaAlO3, LSAT and SrTiO3 buffered Si.
Lithium ion transport in the bronze structure is highly anisotropic. By utilizing substrates with a different orientation to align the more open channels with out-of-plane directions, extremely high rates of lithium ion transport, up to 600C (1C=335 mA g-1), with extraordinary structural stability has been achieved. In a battery half-cell using metallic lithium as counter electrode, the orientation-engineered CaTi5O11 film discharged to 155 mA h g-1 at a rate of 60C, corresponding to a time of 60 s to fully discharge the capacity, at the 100th cycle, delivering specific power of ~20 kW kg-1. Post-mortem examinations by x-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed that both the TiO2-B and CaTi5O11 structures were essentially unchanged after aggressively cycling for more than 60 days. The film microstructure and interfacial atomic structure were characterized by atomic resolution transmission electron microscopy. In addition, we have employed novel in situ TEM to study the Li-intercalation of the films. Revealed by TEM of electrochemical lithiation in TiO2-B, many defects were induced by strain relaxation upon Li-induced TiO2-B lattice expansion. Depending on Li intercalation direction in the crystal structure, either high-symmetry structural transformation or plain shears was generated. These results provide the basic knowledge needed to realize and utilize TiO2-B single crystals, while also supporting theoretical studies with determinate experimental data.
High Performance Pd-CeO2-Nanorods/G Catalyst for the ORR and Its Application in a Microbial Fuel Cell
Authors: Carrillo-Rodriguez J.C. , Alonso-Lemus I.L , Pérez-Hernández R. , Ochoa-Lara M.T. , Espinosa-Magaña F. , Rodriguez-Varela F.J. 
Published: February 2020

Nanostructured Pd-CeO2-NR/G, synthesized with NaBH4 as reducing agent, was evaluated as cathode catalyst for the Oxygen Reduction Reaction (ORR) in 0.5 M KOH and in a Microbial Fuel Cell (MFC) with pH=9.6. Previously, ceria nanorods (CeO2-NR) were synthesized by a hydrothermal method, while graphene (G) was obtained by mechanical milling. Morphological characterization showed agglomerated Pd nanoparticles and CeO2-NR dispersed over graphene. Evaluation of catalytic activity for the ORR in half cell showed a higher mass activity of Pd-CeO2-NR/G relative to Pd/C. The MFC was of the two-chamber type, separated by a Nafion(R) 117 membrane. In the anode, residual water directly from a pharmaceutical company (pH=9.6) was the electrolyte with an anode containing commercial Pt/C. The Bacilus Subtilis microorganism was used to form a biofilm over Pt/C and promote the bioelectrochemical reactions in N2 atmosphere. In the cathode chamber, KOH with pH=9.6 was the electrolyte, which was saturated with O2. The polarization curves from the MFC demonstrated a higher catalytic activity of Pd-CeO2-NR/G than Pd/C. The former delivered an open circuit voltage of 0.26 V and a maximum power density of 12.47 mW m-2.
Effect of Valency of Sn in Sn-Modified Pt-Ru Catalyst on CO Tolerance and HOR Activity for PEFC
Authors: Takeguchi Tatsuya , Sirinutsomboon Bunpot , Wongsawa Thidarat , Ui Koichi 
Published: February 2020

Introduction Pt-Ru on the carbon support has been regarded as a bimetallic catalyst with high CO tolerance for polymer electrolyte fuel cells (PEFCs). The addition of metal oxides such as SnO2 into the carbon support has also been reported to further enhance the CO tolerance1)-2). We have investigated the effect of valency of Sn in Sn-modified Pt-Ru catalyst on CO tolerance and HOR activity.

Experimental Sn in Sn-modified Pt-Ru catalysts was obtained by a rapid quenching method3). Pt-Ru-Sn/C and Ru/SnO2/C catalysts were treated in H2 and He at 800 oC, respectively. The catalysts were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Hydrogen oxidation reaction (HOR) activities of the catalysts were determined by single cell tests.

Results and Discussion The TEM analysis, as shown in Fig. 1, indicates that the particle sizes of Pt-Ru/SnO2/C and Pt-Ru-Sn/C are around 2.5 nm, which are slightly smaller than commercial Pt-Ru/C (TKK, TEC61E54). Since the particle sizes of SnO­­2 are less than 2 nm, the interaction between Pt-Ru and SnO2 is expected. Without the CO contamination, the terminal voltage of the cell using Pt-Ru-Sn/C is 752 mV at the current density of 0.2 A cm-2, which is 18 mV lower than those using Pt-Ru/SnO2/C and Pt-Ru/C (TKK, TEC61E54), as shown in Fig. 2. For Pt-Ru-Sn/C, the heat treatment in H2­ at 800 oC possibly triggers the formation of the trimetallic Pt-Ru-Sn alloy by the reaction Pt-Ru + SnO2 + 2H2 → Pt-Ru-Sn + 2H2O. HOR activities are suppressed by the formation of the trimetallic alloy. On the other hand, the terminal voltage of the cell using Pt-Ru/SnO2/C is as high as 599 mV even in the presence of 1000-ppm CO contamination, which is 27 and 128 mV higher than those using Pt-Ru-Sn/C and Pt-Ru/C (TKK, TEC61E54), respectively. Modification with Sn clearly enhances the CO tolerance. From the above, it is concluded that Sn in the Pt-Ru-Sn alloy reduces the HOR activity, while SnO2 does not. Both of metallic Sn in the Pt-Ru-Sn alloy and SnO2 encourage the CO tolerance.

References

1) T. Takeguchi et al., Catal. Sci. Technol.,
6, 3214-3219 (2016).
2) G. Wang et al., J. Electrochem. Soc.,
156, B862-B869 (2009).
3) T. Takeguchi et al., J. Am. Chem. Soc., 134, No. 35, 14508-14512 (2012).

Acknowledgements

This research was partially supported by the New Energy and Industrial Technology Development Organization (NEDO), Japan.

Figure 1
Unravelling the Degradation Mechanisms of Metal-Based Carbon-Supported Electrocatalysts in Alkaline Medium: Similarities and Differences Compared to Acidic Medium
Authors: Dubau Laetitia , Zadick Anicet , Lafforgue Clémence , Chatenet Marian 
Published: February 2020

Direct liquid alkaline fuel cells (DLAFC), e.g. using performant anion-exchange polymers [1], may viably compete with H2-fed proton-exchange membrane fuel cells for the powering of portable or automotive devices: non-Pt electrodes can be used without detrimental loss of performances and liquid fuel storage is easy versus compressed H2 gas. The common belief considers that AFC electrocatalysts are stable in alkaline environment, owing to the better thermodynamics stability of many metal and oxides at high pH [2]. However, this belief does not apply to carbon-supported Pt nanoparticles (NPs), which undergo massive degradations even for a very mild potential cycling procedure in 0.1 M NaOH [3]. Identical-location transmission electron microscopy (ILTEM) experiments demonstrate that the very pronounced loss of electrochemical surface area (ECSA) is linked to the detachment of the Pt NPs from the carbon support; surprisingly, the latter does not undergo any consequent corrosion, and the Pt NPs seem very stable from a dissolution/redeposition view point (Ostwald ripening). Similar ILTEM experiments demonstrate that carbon-supported palladium NPs (Pd/C) are more stable than Pt/C but still suffer NP detachment from the carbon [4]. The degradation of Pd/C NP is slightly larger when the alkaline electrolyte contains strong reducing species (e.g. hydrogen or hydrazine borane), and this effect is enhanced for small Pd/C NP than for large ones. In contrast with acidic medium, this set of results suggests that the propensity of the metal NPs to be reduced (nobleness) enhances their instability. This hypothesis was further confirmed for non-noble Ni3Co/C NPs, which are more durable than Ni3Ag/C, Ni3Pd/C, Pd/C and Pt/C ones: the link between the carbon support and the NPs is more easily destroyed in liquid alkaline electrolytes when the NPs are containing a noble metal.

References

[1] E.H. Yu, X. Wang, U. Krewer, L. Li, K. Scott, Direct oxidation alkaline fuel cells: from materials to systems, Energy Environ. Sci., 5, 5668, 2012.
[2] M. Pourbaix, Atlas of Electrochemical Equilibria in Aqueous Solutions, in, National Association of Corrosion Engineers, Houston, pp. 453, 1979.
[3] A. Zadick, L. Dubau, N. Sergent, G. Berthomé, M. Chatenet, Huge Instability of Pt/C Catalysts in Alkaline Medium, ACS Catal., 5, 4819, 2015.
[4] A. Zadick, L. Dubau, U.B. Demirci, M. Chatenet, Effects of Pd Nanoparticle Size and Solution Reducer Strength on Pd/C Electrocatalyst Stability in Alkaline Electrolyte, J. Electrochem. Soc., 163, F781, 2016.
Photo/ Catalytic Activation of Carbon Dioxide through Implementation of Plasmonic Metal Nanoparticles
Authors: Solarska Renata , Bienkowski Krzysztof 
Published: February 2020

Investigations of the photo-induced phenomena enabling to improve and understand fundamental processes involved in CO2 reduction includes co-assembly of plasmonic and catalytic metal nanoparticles to the build-up of a semiconductor photocathode. Combination of the nanostructures of plasmonic metals, such as silver or gold with other metal electrocatalysts will substantially decrease the energy barriers of the CO2 reduction process through interaction of photo-excited surface plasmon states with adsorbed reaction intermediates. The significance to investigate reduction of CO2 at gold, silver and copper surfaces enhanced by the extra activation of the process provided by the illuminated, incorporated plasmonic metallic nanostructures is supported by the occurrence of the photo-emission process associated with the decay of photo-excited surface plasmons. Of particular interest will be a strong influence of the Ag/FTO electrode roughness upon the photo-emissive cathodic currents of electro-reduction of CO2 dissolved in aqueous solution. Actually, two metals Ag and Au, the nanostructures of which exhibit strong excitation of surface plasmon resonance through interaction with near UV and visible photons are also catalytically active toward electro-reduction of CO2. Besides the photo-emission, another property of plasmonic NPs – heat generation resulting from the absorption of incident photons and their influence on the reduction of CO2 at composite cathodes will be the objectives of this presentation.
(Invited) Photocatalysis Based on Plasmon-Induced Charge Separation
Authors: Tatsuma Tetsu , Kao Kun-Che , Wu Ling , Kuroiwa Yoshinori , Nishi Hiroyasu 
Published: February 2020

Plasmon-induced charge separation (PICS) occurs at the interface between plasmonic nanostructures of gold, silver, or copper and a semiconductor (typically titanium oxide),1-3 on the basis of carrier transfer from the nanostructure to the semiconductor due to external photoelectric effects including hot carrier injection, or interfacial electron transition.4 We reported PICS for the first time more than 10 years ago1-3 and studied its mechanisms3-7 and applications.1,3,8,9 The applications of PICS include photocatalysis, in particular hydrogen evolution from water. We also work on photocatalytic hydrogen evolution based on PICS by using some different systems including gold nanoparticle/titanium oxide systems and gold halfshell/titanium oxide systems.10

1. Y. Tian and T. Tatsuma, J. Am. Chem. Soc., 127, 7632 (2005).
2. Y. Tian and T. Tatsuma, Chem. Commun., 2004, 1810.
3. T. Tatsuma, Bull. Chem. Soc. Jpn., 86, 1 (2013) [account].
4. E. Kazuma and T. Tatsuma, Adv. Mater. Interfaces, 1, 1400066 (2014).
5. E. Kazuma, N. Sakai, and T. Tatsuma, Chem. Commun., 47, 5777 (2011).
6. H. Nishi and T. Tatsuma, Angew. Chem. Int. Ed., 55, 10771 (2016).
7. K. Saito, I. Tanabe, and T. Tatsuma, J. Phys. Chem. Lett., 7, 4363 (2016).
8. Y. Ohko, T. Tatsuma, T. Fujii, K. Naoi, C. Niwa, Y. Kubota, and A. Fujishima, Nat. Mater.,
2, 29 (2003).
9. Y. Takahashi and T. Tatsuma, Appl. Phys. Lett., 99, 182110 (2011).
10. L. Wu, H. Nishi, and T. Tatsuma, APL Mater., 3, 104406 (2015).
Interplay Between Chemical and Optoelectronic Properties of III/V-Water Interfaces from Ab Initio Simulations
Authors: Wood Brandon C. , Pham Tuan Anh , Ogitsu Tadashi 
Published: February 2020

Photoelectrochemical cells promise sustainable production of hydrogen fuel from water using sunlight, mimicking natural photosynthetic processes. However, finding light-absorbing semiconductor photoelectrode materials that are suitably efficient and also durable under operation has proven challenging. This is largely because electrode durability and efficiency are extremely sensitive to the chemistry at the interface between liquid water and the semiconductor, which is often extraordinarily difficult to probe under operating conditions. In this talk, I will illustrate how ab initio methods have been applied to understand the complex chemistry active at the interface of water with III-V semiconductor photocathodes (GaP, InP, and GaInP2), which offer among the highest solar-to-hydrogen conversion efficiencies but suffer from durability shortcomings. I will show how large-scale ab initio molecular dynamics simulations have assisted in determining the dependence of the available chemical pathways on the surface structure and composition of these materials. I will also show how dynamics simulations can be coupled to many-body perturbation theory to directly probe the link between macroscopic optoelectronic properties and local interfacial chemistry, which is necessary for devising meaningful interface optimization strategies. Finally, I will discuss how combining X-ray photoelectron spectroscopy (XPS) simulations with near-ambient-pressure XPS experiments can identify interfacial chemical speciation under operating conditions. Key differences between InP and GaP will be highlighted, including how different chemistry and mass transport behavior at the interface with water impact relative stability and efficiency. Specific implications for understanding the performance and durability of III-V photocathodes will be discussed, along with some general insights for engineering photoelectrochemical interfaces.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Solar-to-Hydrogen Efficiency: Shining Light on Photoelectrochemical Device Performance
Authors: Young James L , Döscher Henning , Geisz John F , Turner John A , Deutsch Todd G 
Published: February 2020

Direct photoelectrochemical (PEC) hydrogen production aims to provide a clean and cost-effective solar fuel. Solar-to-hydrogen (STH) conversion efficiency is central to evaluating and comparing research results, and it largely establishes the prospect for successfully introducing commercial solar water-splitting systems. Present measurement practices do not follow well-defined standards, and common methods potentially impact research results and their implications. We demonstrate underestimated influence factors and experimental strategies for improved accuracy[1].
Our focus is tandem devices that have the prospect for greater STH efficiency[2], but increased complexity that requires more careful consideration of characterization practices. We perform measurements on an advanced version of the classical GaInP/GaAs design[3] while considering (i) calibration and adjustment of the illumination light-source; (ii) confirmation of the consistency of results by incident photon-to-current efficiency (IPCE), and (iii) definition and confinement of the active area of the device.
We propose applying the following standards for future PEC performance reporting: (i) traceable disclosure of the illumination-source configuration (lamp, filters, optics, PEC configuration) and/or its measured spectral distribution; (ii) thorough device-area definition including confinement of the illumination area and avoidance of indirect light paths; (iii) complementary IPCE confirmation of the solar-generation potential; (iv) proper consideration of faradaic efficiency. We will also give a brief overview of the PEC measurements and capabilities available at NREL to support academic and industry research.
[1] H. Döscher, J. L. Young, J. F. Geisz, J. A. Turner, and T. G. Deutsch, “Solar to hydrogen efficiency: Shining light on phoelectrochemical device performance,” Energy Environ. Sci. 2015.
[2] H. Döscher, J. F. Geisz, T. G. Deutsch, and J. A. Turner, “Sunlight absorption in water – efficiency and design implications for photoelectrochemical devices,” Energy Environ. Sci. 2014.
[3] O. Khaselev and J. A. Turner, “A Monolithic Photovoltaic-Photoelectrochemical Device for Hydrogen Production via Water Splitting,” Science. 1998.
Evaluation of Material Properties and Performance of Zinc Ferrite (ZnFe2O4) for Photoelectrochemical Water-Splitting
Authors: Bright Joeseph , Wu Nianqiang 
Published: February 2020

With greenhouse gases such as methane and carbon dioxide contributing significantly to global climate change, sustainable, carbon-neutral fuels are needed to replace fossil fuels for meeting society’s energy needs. A possible replacement for fossil fuels for energy is hydrogen gas derived from photoelectrochemical (PEC) water-splitting. However, existing materials capable of driving photoelectrochemical water-splitting have several problems not limited to poor light absorption at visible wavelengths that compromise the sunlight, poor charge transport within the material, and/or poor photo-stability in aqueous electrolyte solutions. Therefore, new materials must be developed or efforts must be made to solve the issues of existing materials for PEC water-splitting.
Zinc ferrite (ZnFe2O4) is a n-type, narrow bandgap (Eg = 1.9 eV) semiconductor with a sufficiently positive valence band to drive PEC water-splitting as a photoanode. However, ZnFe2O4 suffers from multiple issues that lower its performance for PEC water-splitting such as extremely poor conductivity, poor light absorption despite its narrow bandgap due to the bandgap’s indirect nature, and poor surface catalytic activity. This work fundamentally studies ZnFe2O4 by quantifying its optical, electrical, and catalytic properties and comparing these properties to other established materials for PEC water-splitting. Based on this study, the critical limiting factors for ZnFe2O4’s implementation as a photoanode for PEC water-splitting will be discussed.
(Invited) Atomic-Scale Surface Science Investigations for Understanding and Producing Electrochemical Interfaces
Authors: Diebold Ulrike 
Published: February 2020

Key ingredients in solid-state electrochemistry are charge transfer to, and adsorption/reaction of molecules, both heavily influenced by the availability of charge carriers and O vacancies. Surface science techniques, in particular Scanning Tunneling Microscopy (STM) in combination with surface spectroscopy, can help unravel how these processes happen at the atomic scale. The talk will showcase several examples of STM studies of adsorption and reaction of O2 and H2O on titania and selected perovskite materials. It will also exemplify how STM can be used to judiciously steer thin film growth in in Pulsed Laser Deposition (PLD) towards fabricating model electrodes with a desired surface structure, which could help increasing functionality in electrochemical devices.
Importance of the Formation of Dy4+ in BaZr0.9Dy0.1O3-δ proton-Conducting Ceramics in Oxidizing Atmospheres
Authors: Ricote Sandrine , Hudish Grant , Beedle Christopher , Tsoi Stanislas , Owrutsky Jeffrey C. , O Brien James 
Published: February 2020

Yttrium doped barium zirconate, BaZr1-xYxO3-δ, has been one of the most studied high temperature proton conductors for the last two decades [1]. Several research groups focused on the choice of the trivalent dopant, which is necessary to create the oxygen vacancies required for the hydration of the material. Han et al. studied for example Sc, Sm, Eu and Dy dopants [2-4] and reported the presence of Dy4+in oxidizing atmospheres.
In this work, we are interested in the comparison of structural and electrical properties between the well-known BZY10 (BaZr0.9Y0.1O3-δ) and BZDy10 (BaZr0.9Dy0.1O3-δ). A wide combination of experiments was used to confirm the presence of Dy4+ in oxidizing atmosphere, including high temperature X-ray diffraction, Raman spectroscopy, SQUID magnetometry and electron spin resonance (ESR or EPR). Figure 1 summarizes the BZDy10 lattice parameter in dry oxidizing atmosphere as a function of temperature and shows a decrease in the lattice parameter when increasing the oxygen partial pressure. This is explained by the difference in Dy radii in VI coordination: 0.78 Å and 0.912 Å for Dy4+ and Dy3+respectively.
Conductivity measurements as a function of pO2in dry and moist conditions were performed for both BZY10 and BZDy10. The two materials behaved quite similarly in moist reducing atmosphere (i.e., pure ionic conduction), while significant differences were noticed in oxidizing atmospheres.
[1] Fabbri E., Pergolesi D. and Traversa E., “Materials challenges toward proton-conducting oxide fuel cells: a critical review ”, Chem. Soc. Rev 39, 4355-4369 (2010)
[2] D. Han, K. Shinoda, T. Uda, Dopant site occupancy and chemical expansion in rare earth-doped barium zirconate, J. Am. Ceram. Soc. 97 (2014) 643-650
[3] D. Han, T. Uda, Y. Nose, T. Okajima, H. Murata, I. Tanaka and K. Shinoda, Tetravalent Dysprosium in a Perovskite-Type Oxide, Advanced Materials 24 (2012) 2051-2053
[4] D. Han, K. Shinoda, S. Sato, M. Majima, T. Uda, Correlation between electroncutive and structural properties of proton conductive acceptor doped barium zirconate, J. Mater. Chem. A, 13 (2015) 1243-1250

Figure 1