bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fast Near-Infrared Electrochromism of Redox-Active Plasmonic Copper Sulfide Nanoparticles
Authors: Nishi Hiroyasu , Asami Keisuke , Tatsuma Tetsu 
Published: February 2020

Metal nanoparticles absorb and scatter light strongly on the basis of resonance of free electron oscillation with incident light, which is denoted as localized surface plasmon resonance (LSPR). Especially, gold and silver nanoparticles are known to exhibit LSPR in the visible and near-infrared (NIR) regions and applied to sensors,1 photovoltaics and photocatalysis,2 and photochromic materials.3 The LSPR properties such as resonant wavelength and intensity depend significantly on particle size and shape, local refractive index, and interparticle distance. Those are also dependent on electron density of the nanoparticles, which can be controlled electrostatically.4-6 However, it is difficult to induce large changes in resonant wavelength and intensity by the electrostatic means.
Here, we focus on plasmonic copper sulfide nanoparticles as an electrochromic material. Nanoparticles of copper sulfide, represented by Cu2-x
S, have sufficient holes to exhibit LSPR in the NIR region.7 In addition, copper valence can be controlled reversibly by chemical redox reactions,8 suggesting that reversible electrochemical tuning of their LSPR properties is possible. However, such a redox reaction-based control of LSPR has not been reported so far.
Covellite (CuS) nanoparticles were prepared by heating copper(I) chloride and elemental sulfur in a mixture of oleylamine and oleic acid under N2 atmosphere9 and deposited on an ITO electrode. The figure shows absorption spectra of the electrode at different potentials (vs. Ag|AgCl) in deuterated water containing 0.1 M Na2S. Broad absorption due to LSPR is observed in the NIR region at -0.6 V while that gradually disappears as the applied potential is shifted negatively, indicating that plasmonic copper(II) sulfide is reduced to non-plasmonic copper(I) sulfide.10 It is noteworthy that reductive disappearance and oxidative reappearance of LSPR can be repeated at least 12 cycles and the response time is a few seconds. These results indicate that copper sulfide nanoparticles can be applied to fast NIR electrochromic devices that are driven in a narrow potential range (~0.4V).

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2013, 52, 13671.
9. H. Nishi, K. Asami, T. Tatsuma, Opt. Mater. Express
2016, 6, 1043.
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2012, 134, 1583.

Figure 1
Virus-Assisted Growth of Metal Alloy Nanostructure and Its Use an Electrocatalyst
Authors: Kim Kyuwon , Seo Yeji , Kang Inhak , Manivannan Shanmugam 
Published: February 2020

We report an engineered M13 virus (MV) as a scaffolds to electrodeposit well dispersed Au–Pt alloy nanostructures at bio-template, which represents a new type of MV/R/Au–Pt hetero structure .Amine-functionalized sol–gel matrix (T)/MV/R composite is prepared and attachment of Au binding peptide sequences along the major coat protein of MV enables specific nucleation cites, where growth of Au–Pt alloy nanostructures occurred. The electrocatalytic activity of the Au–Pt catalyst towards methanol oxidation was investigated. At this bio-template, MV ensures a close contact between Au–Pt alloy nanostructures and R besides it facilitates the OH– rich environment to the catalyst. As a result, efficient electron transfer and the synergistic catalytic acivity for methanol oxidation were observed.
(Invited) Electrocatalysts for Solar-to-Chemical Conversion
Authors: Min Byoung Koun , Hwang Yun Jeong 
Published: February 2020

Solar-chemical production inspired from photosynthesis in nature has attracted much attention due to a need for developing sustainable technology for future energy as well as chemical resources. In this study, we demonstrate a highly efficient solar energy to chemical conversion device using CO2 and water as feedstock. Among many core technologies for the realization of this architecture electrocatalysts for both water oxidation and CO2 reduction are critically important because the overpotential for solar-chemical device operation and the product from CO2 are strongly dependent on the catalytic function of electrodes. To perform selective production of CO from CO2 in water nanostructured gold and silver electrocatalyst were successfully synthesized based on the method of oxidation and subsequent reduction cycle. In addition, water oxidation was very efficiently carried out by a stainless steel based electrocatalyst in low overpotential conditions. The details of the synthetic method and characterization of the electrocatalysts and the solar-chemical generation system will be discussed in the presentation.
(Invited) Latest Development in Design Strategies for Efficient Solar Water Splitting Photoelectrodes
Authors: Vayssieres Lionel 
Published: February 2020

An overview of a decade of research on metal oxide semiconductor design [1], electronic structure [2] and applications for solar energy conversion and solar hydrogen generation [3-5] will be presented. Latest advances in design strategies [6] and nanodevice fabrication for efficient low cost solar (sea)water oxidation without sacrificial agents will be demonstrated. Visible-light active photocatalyst heteronanostructures based on non toxic and earth abundant materials engineered to efficiently drive aqueous chemical reactions at their interfaces have been fabricated and tested intensively. Their surface chemistry [7], structural, optical, electrical [8], photoelectrochemical, dimensionality effects [9] and interfacial electronic structure [10] along with their efficiency have been thoroughly investigated at synchrotron radiation facilities as well as in our laboratories. The most promising structures for low cost and large scale solar water splitting will be discussed [11].
References
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89, 1 (2007); Int. J. Nanotechnol. 4, 750 (2007); Int. J. Nanotechnol.
1, 1 (2004); Angew. Chem. Int. Ed.
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72, 47 (2000)
[2] F. J. Himpsel et al, J. Electron Spectrosc. Relat. Phenom. 190, 2 (2013); C.X. Kronawitter et al, PhysChemChemPhys
15, 13483 (2013); C. L. Dong et al, Phys. Rev. B
70, 195325 (2004); J.-H. Guo et al, J. Phys.: Condens. Matter
14, 6969 (2002)
[3] Y. Tachibana, L.Vayssieres, J. R. Durrant, Nat. Photonics
6, 511 (2012)
[4] C.X. Kronawitter et al, Energy Environ. Sci.
7, 3100 (2014); Energy Environ. Sci.
4, 3889 (2011)
[5] On Solar Hydrogen & Nanotechnology, L. Vayssieres ed. (Wiley, 2009), Ch. 17, pp. 523-558
[6] Y.K. Wei et al, Nano Res. (2016) in press
[7] L. Vayssieres, J. Phys. Chem. C
113, 4733 (2009); Int. J. Nanotechnol. 2, 411 (2005);
[8] J. Engel et al, Adv. Funct. Mater.
24, 4952 (2014)
[9] L. Vayssieres et al, Appl. Phys. Lett.
99, 183101 (2011); Adv. Mater.
17, 2320 (2005)
[10] C.X. Kronawitter et al, Nano Lett.
11, 3855 (2011); Phys. Rev. B
85, 125109 (2012); J. Phys. Chem. C
116, 22780 (2012)
[11] J.Z. Su and L.Vayssieres, ACS Energy Lett. Invited review (2016)
(Invited) Generation of Hot Plasmonic Electrons and Heat in Nanocrystals with Hot Spots
Authors: Govorov Alexander O. 
Published: February 2020

The efficiency of generation of energetic plasmonic carriers in metal nanostructures strongly depends on the optical design and material composition. This study demonstrates the ability to generate large numbers of hot plasmonic carriers in specially-designed hybrid nanostructures [1,2]. The hot-electron generation becomes especially efficient in plasmonic nanostructures with electromagnetic hot spots [1]. The energy distribution of optically-excited plasmonic carriers is very different in metal nanocrystals with large and small sizes [2]. For metal nanocrystals with smaller sizes (less than 10nm) or in nanostructures with hot spots, the excited state gets a large number of carriers with high energies. Nanostructures with a strong plasmonic enhancement generate unusually large numbers of energetic electrons, which can be observed using ultra-fast spectroscopy, photo-currents and photo-chemistry [1,3,4]. Along with the hot-electron generation, which is a quantum effect, the electromagnetic radiation typically causes efficient heating in metal nanostructures, which may also be concentrated in thermal hot spots [5]. The results obtained in this study can be used to design plasmonic hot-electron nanodevices for photo-catalysis, photo-detectors and solar-energy applications.

[1] H. Harutyunyan, A. B. F. Martinson, D. Rosenmann, L.K. Khorashad, L.V. Besteiro, A.O.Govorov, and G.P. Wiederrecht, Nature Nanotechnology 10, 770–774 (2015).
[2] A.O. Govorov, H. Zhang, V. Demir, and Y. K. Gun’ko, NanoToday 9, 85 (2014).
[3] ] W. Li, Z. J. Coppens, L. Vázquez, W. Wang, A. O. Govorov, and J. Valentine, Nature Communications 6, 8379 (2015).
[4] L. Weng, H. Zhang, A. O. Govorov, and M. Ouyang, Nature Communications 5, 4792 (2014).
[5] A. Govorov and H.H. Richardson, NanoToday 2, 20 (2007).
(Invited) Development of Wide Bandgap Copper Chalcopyrite Materials for Economical Photoelectrochemical Hydrogen Production
Authors: Gaillard Nicolas , DeAngelis Alexander , Horsley Kimberly 
Published: February 2020

Photoelectrochemistry (PEC) is theoretically one of the most efficient methods to produce alternative fuels, although the efficiency, cost, and durability of lab-scale systems are currently not at the level required to make this technology economically feasible. The chalcopyrite material class provides exceptional candidates to meet the requirements for cheap, sustainable solar fuels production. As we have previously reported, co-evaporated 1.7 eV CuGaSe2 offers very high-saturated photocurrent densities (>15 mA.cm-­2) and high Faradaic efficiency (>85%). However, CuGaSe2 photocathodes suffer from non-ideal surface energetics, requiring additional PV cells to drive the water splitting process. The hybrid photo-electrode (HPE) device, in which a PEC electrode is placed on top of a solar cell, is by far the most efficient approach for unbiased solar water splitting. Unfortunately, CuGaSe2’s narrow bandgap prohibits this integration scheme.
In the present communication, we report on our efforts to synthesize 1.8-2.2 eV band-gap chalcopyrite materials for PEC water splitting. Specifically, we investigated the effect of sulfur on the optical and photoelectrochemical characteristics of the copper chalcopyrite material class. Using co-evaporated 1 μm-thick CuGaSe2 as a baseline system, we demonstrate that the substitution of selenium with sulfur can be accomplished through a simple annealing step. As a result, a dramatic change in optical properties was observed, with a bandgap increase from 1.6 eV (CuGaSe2) to 2.4 eV (CuGaS2). Then, by simply adjusting the indium content during the initial growth process, the bandgap of sulfurized copper chalcopyrite was decreased from 2.4 eV to 2.0 eV. X-ray diffraction data indicated successful bulk sulfurization by the shift of the prominent (112), (220), and (312) reflections to higher angles. Saturated photocurrent densities of 5 mA/cm2 were achieved with 2.0 eV red CuIn0.3Ga0.7S2 photocathodes in 0.5M H2SO4 under AM1.5G simulated illumination. From this proof of concept experiment, we have further developed new synthesis approaches and innovative characterization protocols to achieve PV-grade wide bandgap sulfide-based chalcopyrites capable of generating photocurrent densities over 10 mA.cm-2.
(Invited) Computational Design of Chalcopyrite Photoabsorber for Photoelectrochemical H2 Production Cell
Authors: Ogitsu Tadashi , Varley Joel , Zhou Fei , Lordi Vincenzo , Gaillard Nicolas 
Published: February 2020

The chalcopyrite material class presents excellent candidates for PEC water splitting due to the high tunability of band gaps. An optimal band gap for the front absorber (~1.8eV) is larger than that for a PV cell and is unattainable with conventional selenide-based chalcopyrites (e.g. CuInGaSe2). We have investigated the stability and electronic structure of related alloys within a broader group I-III-VI2 system (I=Ag,Cu ; III=In,Ga,Al ; VI=S,Se) to identify desirable compositions for optimal absorbers, using hybrid density functional theory for reliable predictions. In this presentation, we will assess the suitability of such alloys in a comprehensive manner, considering properties, in addition to band gap, that include the thermodynamic stability, the propensity for incorporation of various types of defects under given synthesis conditions, the impact of defects on the electronic properties, and the availability of appropriate buffer materials.
This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by the Department of Energy office of Energy Efficiency & Renewable Energy (EERE).
(Invited) Bioinspired Water Oxidation and CO2 Reduction Electrocatalysts
Authors: Nam Ki Tae 
Published: February 2020

Water splitting is regarded as a promising step towards environmentally sustainable energy schemes because electrolysis produces only hydrogen and oxygen, without any by-products. Within the overall water splitting process, the oxygen evolution reaction (OER), an anodic half-cell reaction that generates an oxygen molecule from two water molecules, requires extremely high overpotential due to its slow reaction kinetics. In this regard, development of cost-effective and robust catalyst has been demanding challenge to solve the modern energy crisis. In nature, there exists a water oxidation complex (WOC) in photosystem II (PSII) comprised of the earth-abundant elements Mn and Ca. The WOC in PSII, in the form of a cubical Mn4CaO5 cluster, efficiently catalyzes water oxidation under neutral conditions with extremely low overpotential value (~160 mV) and a high turnover frequency (TOF) number (~25,000 mmolO2 mol-1
Mn s-1). Inspired from the asymmetric geometry and flexible ligation of the biological CaMn4O5 cluster, we designed new manganese based water oxidation catalysts, Mn3(PO4)2-3H2O and Li2MnP2O7.
We first identified a new crystal structure, Mn3(PO4)2-3H2O, and demonstrated its superior catalytic performance at neutral pH. From the combined ex-situ spectroscopic analysis and DFT calculations, we revealed that structural flexibility can stabilize Jahn-Teller distorted Mn(III), and thus facilitate Mn(II) oxidation during catalytic cycle. We also studied a new pyrophosphate based Mn compound, Li2MnP2O7 for water oxidation catalysis. We verified the influence of oxidation state of Mn and asymmetric Mn geometry on water oxidation catalysis using Li2MnP2O7 and its derivatives. We believe higher Mn(III) portion and asymmetric arrangement of Mn atoms which can be seen in the WOC, enhance catalytic water oxidation reaction.

Specific questions that our group intensively focus for the further applications include 1) how we can translate the underlying principles in Manganese Calcium Clusters into the synthetic heterogeneous catalysts and 2) how we can mimic the redox molecule involved biological dark reaction for the CO2 reduction. Toward this vision, we have been developing a new catalytic platform based on sub-10 nm uniform nanoparticles to bridge the gap between atomically defined biological catalysts or their metalloenzyme counterparts and the scalable, electrode depositable heterogeneous catalysts. In this approach, the local atomic geometry is controlled by the nitrogen containing graphitic carbon and the heterogeneous atom doping, that enhance the catalytic activity and selectivity. Additional surface modification by the specific ligand allow for the atomic scale tunability to realize the unique electronic hybridization.
(Invited) Photocatalytic CO2 Conversion to Selective Hydrocarbons Using Graphene Oxides and Related 2D Hybrids
Authors: Chen Li-Chyong , Lien Hsiang-Ting , Shown Indrajit , Chen Kuei-Hsien 
Published: February 2020

Photocatalytic conversion of carbon dioxide (CO2) to hydrocarbons makes possible simultaneously harvesting solar energy for production of fuels or useful chemicals, as well as reducing CO2 for a greener society, two birds with one stone for the pressing global energy and environmental problems of our time. Here, we describe a highly efficient photocatalytic conversion of CO2 to selective hydrocarbons using graphene oxides (GOs) and their related 2D hybrids as photo-catalysts. Several approaches have been employed to synthesize GOs and reduced GOs (rGOs) with tunable bandgap and band alignment with respect to the CO2 reduction level. The functionalities of the GOs/rGOs were investigated by UV-Vis, cyclic voltammetry, and x-ray photoemission spectroscopy.
Under visible light, the photocatalytic conversion of CO2 to methanol of GOs/rGOs is several-fold higher than that of TiO2 (e.g., commercial P-25). Further, metal and metal sulfides, especially the 2D materials such as MoS2, as well as optically active polymers, were deposited onto GO as co-catalysts or sensitizers, to enhance the photocatalysis reaction. Besides methanol, other selective hydrocarbons including acetaldehyde were also detected. Total solar to fuel yield of ~200 times enhancement over that of P-25 has been achieved. In all these GOs-2D hybrids, the photo-catalytic performance is always much better than that of constituent component when used alone. Detailed preparation and characterization of the catalysts will be presented. The role and interplay of the constituent components will also be discussed.
CoP As an Acid-Stable Electrocatalysts for the Hydrogen-Evolution Reaction: Synchrotron-Based Operando Oxidation-State Determinations
Authors: Saadi Fadl Hussein , Carim Azhar I , Drisdell Walter , Yano Junko , Lewis Nathan S. , Soriaga Manuel P. 
Published: February 2020

Electrochemical water splitting is an important component of several developing clean-energy technologies that aim to be sustainable, renewable, and carbon-neutral. In order to carry out this process efficiently, catalysts for the cathodic half reaction (hydrogen evolution, HER) and anodic half reaction (oxygen evolution, OER) are essential. Currently, earth-abundant, low-cost materials are being vigorously sought for these purposes. Here we report a facile electrochemical method for the synthesis of a cobalt phosphide film that displays both excellent HER activity and stability during operation in acidic media.
CoP films were synthesized electrochemically via cathodic deposition from oxidized precursors in aqueous solution at room temperature. The as-deposited films required an overpotential of only 85 mV to drive a current density of 10 mA cm−2 in 0.5M H2SO4. Over 24 h of galvanostatic electrolysis at 10 mA cm-2 resulted in an overpotential increased of less than 20 mV.
X-ray photoelectron spectroscopic examination of the film surface after electrocatalysis revealed that the phosphorus existed in both reduced (phosphide) and oxidized states (orthophosphate). In order to determine the surface character during electrocatalysis operando X-ray absorption and Raman spectroscopic analysis were performed. Such analysis directly confirmed that the catalyst existed solely in the reduced state (phosphide) during catalysis.
Tuning the Exposed Facets of Photocatalysts to Improve the Performance
Authors: Zhang Junying 
Published: February 2020

Exposed crystal facets of the photocatalysts are one of the most important factors to determine the photocatalytic activities. We investigated several photocatatlysts, revealing the relationship between the morphology, especially the exposed facets, and the photocatalytic activities.
Cu2O microcrystals demonstrate better performance in producing hydrogen by degrading formaldehyde solution under visible light in comparison with other materials. Cu2O microcrystals exposing {110} facets show higher activity than Cu2O exposing {111} facets because of a larger density of surface copper atoms.
BiOCl microsized square nanosheets exposing {001}facets, with a large lateral size of 3−5 µm and the side length/thickness ratio of about 100, present good photocatalytic activity toward decoloring Rhodamine B solution under the ultraviolet-visible light irradiation.
{020} is the active facet of orthorhombic WO3•0.33H2O. The orthorhombic WO3•0.33H2O exposing most {020} facets shows much higher activity than other samples in decoloring Rhodamine B solution under visible light.
LaTi2O7, with the layered perovskites structure, prefers to grow into nanosheets exposing the {010} facets. By exposing small {012} facets with high surface energy, the photocatalytic hydrogen releasing rate has been substantially increased.

References

Min Li, Junying Zhang, Hong Gao, Feng Li, Sten-Eric Lindquist, Nianqiang Wu, Rongming Wang, ACS Applied Materials & Interface, 2016, 8, 6662−6668

Yesheng Li, Zilong Tang, Junying Zhang, Zhongtai Zhang, CrystEngComm, 2015, 17, 9102-9110

Hong Gao,Junying Zhang, Rongming Wang, Mei Wang, Applied Catalysis B: Environmental, 2015, 172, 1-6
Solid-State Characterization of Wide-Bandgap Cuga(S,Se)2 for PEC Water Splitting
Authors: DeAngelis Alexander D , Horsley Kimberly , Gaillard Nicolas 
Published: February 2020

The development of a semiconductor of bandgap 1.7 – 2.1 eV that is both highly efficient and stable is necessary for an economically viable water splitting device to produce clean and renewable H2. Copper chalcopyrites are excellent candidates for this purpose, as they output current densities close to their theoretical maximum, tend to be relatively durable compared to other material systems used for PEC applications, and can theoretically be engineered to have a bandgap from 1.0 to 3.0 eV. This material class covers a wide range of elements, many of which have yet to be explored.
In this work, we have focused on the CuGa(S,Se)2 (CGSSe) alloy, which has been theoretically shown to have a bandgap within the ideal energy range. By our process, we have been able to successfully synthesize CGSSe films with a bandgap ranging from 1.7 to 2.4 eV. Preliminary PEC measurements under AM1.5 illumination on these materials exhibit current densities exceeding 10 mA/cm2 (equivalent to STH efficiencies in the 10-12% range) along with an anodic shifting of the photocurrent-onset voltage by approximately 0.3 V, relative to that of CuGaSe2. However, the PEC devices suffer from a highly negative photocurrent onset of about -0.3 V vs Ag/AgCl, most likely due to the generally poor energy band alignment of copper chalcopyrites with water splitting redox potentials. To circumvent this energetics problem, we have taken the so-called buried junction approach, creating an internal electric field to anodically shift the onset voltage. Thus, PV devices were studied as an archetype of our ultimate stand-alone device. Solid-state PV devices made with our champion CGSSe materials so far yield approximately a short-circuit photocurrent density of 5 mA/cm2, an open circuit voltage of 650 mV, and a fill factor of 55 %. Further discussion of how the different facets of the synthesis process can be changed to improve device performance will be presented.