bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Surface Area NanoCOT Catalysts on Ni Foam Framework for Efficient Water Electrolysis
Authors: Dyer Elizabeth , Hitt Jeremy , Shan Zhichao , Pan Shanlin 
Published: February 2020

Carbon doped nanostructured TiO2 electrodes (NanoCOT) are prepared by anodizing titanium in a fluoride-based electrolyte followed by thermal annealing in an atmosphere of methane and hydrogen in the presence of Fe precursors. NanoCOT are highly conductive and contain more than 1 × 10^9 /cm2 of nanowires or nanotubes to enhance their double layer charge capacitance and electrochemical stability. This electrode material also exhibits enhanced oxygen evolution reaction (OER) catalytic activity in alkaline solution, providing a current density of 1.33 mA/cm2 at an overpotential of 0.42 V. This OER current density of a NanoCOT electrode is about 4 times higher than an oxidized Ir electrode and 15 times higher than a Pt electrode because of its nanostructured high surface area and favorable OER kinetics. The enhanced catalytic activity of NanoCOT is attributed to the presence of a continuous energy band of the titanium oxide electrode with predominantly reduced defect states of Ti (e.g., Ti^1+, Ti^2+, and Ti^3+) formed by chemical reduction with hydrogen and carbon. The OER performance of NanoCOT can also be further enhanced by decreasing its overpotential by 150 mV at a current density of 1.0 mA/cm2after coating its surface electrophoretically with 2.0 nm IrOx nanoparticles. Further improve can be obtained by using porous substrate such as Ni and Ti foam.
(Invited) Developing Efficient Electrocatalysts for the Hydrogen and Oxygen Evolution Reactions
Authors: Yeo Boon Siang 
Published: February 2020

Water electrolysis is one of the crucial means for converting electricity generated from solar and wind based power sources into clean H2 fuels. The efficiency of this process depends largely on the catalytic property of the cathode and anode.We present here our work to develop and understand electrocatalysts used for the oxygen (OER) and hydrogen (HER) evolution reactions. Using operando Raman spectroscopy, we shall first show how the structure of amorphous MoS
x
(an excellent HER catalyst) evolves during H2 evolution. Furthermore, we have identified the S atoms therein as the catalytically active sites responsible for proton reduction. Density functional theory calculations were performed on a variety of MoS
x
structures and corroborated the assignments of the observed vibrational frequencies. We shall also present our Raman and X-ray absorption spectroscopy study of Cu oxides during O2 evolution. This investigation has allowed us to propose CuIIIoxides as highly active catalytic species for the electrochemical water oxidation. Mixed metal composites based on Mo and W have also been shown to exhibit excellent HER activities. We elucidated the catalytic roles of the different elements therein such as nitrogen, carbon, molybdenum, etc , and proposed plausible mechanisms of their workings. We shall show that some of these catalysts are robust against deactivation even in contaminated electrolytes. Finally, we present an overview of our recent work to couple photovoltaics to an electrocatalytic cell for the efficient reduction of carbon dioxide.
1. Y.L. Deng, L.R.L. Ting, P.H.L. Neo, Y.J. Zhang, A.A. Peterson, and B.S. Yeo. ACS Catal. 6, 7790.
2016.

2. Y.L. Deng, A.D. Handoko, Y.H. Du, S.B. Xi and B.S. Yeo. ACS Catal. 6, 2473. 2016

3. L.R.L. Ting, Y.L. Deng, L. Ma, Y.J. Zhang, A.A. Peterson, and B.S. Yeo. ACS Catal. 6, 861. 2016

4. U. Joshi, J. Lee, C. Giordano, S. Malkhandi and B.S. Yeo. Phys. Chem. Chem. Phys. 18, 21548. 2016.
(Invited) Shape Fixing By Salt Nanoreactor to Produce Nanocarbon Materials for the Catalysis of Oxygen Reduction Reaction
Authors: Wei Zidong , Ding Wei , Li Li , Chen Siguo , Qi Xueqiang 
Published: February 2020

Developing catalytic materials for oxygen reduction reactions (ORR) with high performance and low cost has been one of the major challenges for large-scale applications of fuel cells. We demonstrated a high-yield " shape fixing via salt recrystallization" method to efficiently synthesize N-doped carbon nanomaterials with a high density of active sites, as an ORR catalyst. The process of shape-fixing involves pouring a supersaturated sodium chloride (NaCl) solution onto a 3D polyaniline (PANI) carbon-based polymer in a beaker, which results in the water evaporating and NaCl recrystallizing around the PANI until the PANI is fully covered by crystals. The NaCl crystal functions as a fully sealed nanoreactor which facilitates the N incorporation and graphitization. The gas from gasification in such a closed nanoreactor produces a large quantity of pores in resultant samples, and the carbonized PANI retains its original 3D shape due to previously being shape-fixed by the NaCl crystal. This makes it possible for the active sites (activated by planar pyridinic and pyrrolic N atoms with sp2 hybrid orbitals, which only appear at the outside fringe of a graphene sheet) to appear in large quantities on the edges of numerous pores. Such favorable catalyst structure leads to the availability of efficient mass transport pathways and a high utilization of the active sites in fuel cell. It results in an excellent ORR activity with a half-wave potential only 58 mV behind that of Pt/C in an acidic medium. The proton-exchange membrane fuel cells with the CPANI-Fe-NaCl-catalyzed cathode outputs a peak power of 600 mW cm-2, which is among the best for non-precious metal catalysts reported so far for the ORR. Additionally, no other method is comparable to this invention, in terms of its high yield per batch of N-doped carbon catalysts. The “shape fixing via salt recrystallization” method represents a powerful approach for the preparation of high-performance carbon nanostructures by confined pyrolysis of nanopolymers and, more importantly, provides insight into the design of advanced PEMFC cathode catalysts.
References
[1] W. Ding, Z. D. Wei, S. G. Chen, X. Q. Qi, T. Yang, J. S. Hu, D. Wang, L.-J. Wan, S. F. Alvi, L. Li. Angew. Chem. Int. Ed.
2013, 52, 11755.
[2] W. Ding, L. Li, K. Xiong, Y. Wang, W. Li, Y. Nie, S. G. Chen, X. Q. Qi, Z. D. Wei. J. Am. Chem. Soc.,
2015, DOI: 10.1021/jacs.5b002.
In Situ Investigation of the Interface of Photoanodes and Electrocatalysts in Photoelectrochemical Water Oxidation Using Dual Working Electrode Photoelectrochemistry
Authors: Qiu Jingjing , Nellist Michael R. , Laskowski Forrest A. L. , Boettcher Shannon W. 
Published: February 2020

Light-absorbing semiconductor electrodes decorated with electrocatalysts are key components of photoelectrochemical energy conversion and storage systems. Efforts to optimize these systems have been slowed by an inadequate understanding of the semiconductor (SC) and electrocatalyst (EC) interface. Experiments to directly measure the interface behavior are challenging because conventional photoelectrochemical techniques do not measure the electrocatalyst potential during operation. We developed dual working electrode (DWE) photoelectrochemistry to address this limitation. A second electrode is attached to the catalyst layer to control and probe current/voltage independent from that of the semiconductor.
The DWE investigations on a model system TiO2 reveal that electrolyte-permeable ECs form an “adaptive” junction with the semiconductor. This talk will focus on studies of the interface of the visible-light-absorbing semiconductor α-Fe2O3 and the electrocatalyst a-Ni80Fe20O
x
with DWE photoelectrochemistry. We discover that the potential at the SC|EC interface changes in situ with the oxidation level of the EC. Additionally, the activation of EC film is vital to the charge transport between SC and EC. A fully-activated amorphous Ni(Fe)OOH film can harvest the vast majority of photo-generated holes from α-Fe2O3 electrodes.
(Invited) Modification of Electrocatalytic and Photoelectrochemical Interfaces Toward More Efficient Reduction of Carbon Dioxide
Authors: Kulesza Pawel J , Wadas Anna , Szaniawska Ewelina , Zoladek Sylwia , Rutkowska Iwona Agnieszka 
Published: February 2020

There has been growing interest in the photoelectrochemical conversion of carbon dioxide to useful carbon-based fuels or chemicals. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large overpotentials. It is often postulated that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. In this respect, the proton availability and its mobility at the photo(electro)chemical interface has to be addressed. On the other hand, competition between such parallel processes as hydrogen evolution and carbon dioxide reduction has also to be considered.
Recently, we have concentrated on the development of hybrid materials by utilizing combination of metal oxide semiconductors thus capable of effective photoelectrochemical reduction of carbon dioxide. For example, the combination of titanium (IV) oxide and copper (I) oxide has been considered before and after sunlight illumination. Application of the hybrid system composed of both above-mentioned oxides resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol (CH3OH) as demonstrated upon identification of final products. Among important issue is intentional stabilization, activation, and functionalization of the mixed-metal-oxide-based photoelectrochemcal interface toward better long-term performance and selectivity production of small organic molecules (C1-C4) and other chemicals. In this respect, ultra-thin films of conducting polymers (simple or polyoxometallate-derivatized) and supramolecular complexes (with nitrogen containing ligands and certain transition metal sites), sub-monolayers of metals (Cu, Au), networks of noble metal (Au, Ag) nanoparticles or layers of robust bacterial biofilms have been considered.
We are also going to demonstrate that the photoinduced electron from semiconductor conduction band is capable of activation of the active center of the metalo-enzyme molecule. Here the.nanostructured silicon material has been chosen as the substrate for the enzyme adsorption. In this case the p-type Si(111) was etched toward formation of the bunched steps on the surface. The photo-biocathode with Cu-containing enzyme has induced the reduction of not only oxygen but carbon dioxide as well, under illuminations with photon energies higher than silicon band gap.
In the presentation, special attention will be paid to mechanistic aspects of electroreduction of carbon dioxide, fabrication and characterization of highly selective and durable semiconductor photoelectrode materials and to importance of the reaction conditions.
Effect of CdSe Quantum Confinement on Charge Transfer Kinetics in Solar-Driven Hydrogen Production from Urea
Authors: Radich James , Zhao Rong 
Published: February 2020

Urea has been proposed as a source to produce hydrogen. We describe here CdSe-sensitized TiO2 assembled with urea electrocatalyst, Ni(OH)2, on fluorine-doped tin oxide (FTO) coated glass (FTO/TiO2/CdSe/Ni(OH)2) used as photoanode for simultaneous urea oxidation and water reduction using visible light irradiation. The steady-state photoresponse of the semiconductor-catalyst electrode in the photoelectrochemical system is investigated, and the CdSe quantum confinement effect on charge transfer kinetics is investigated by employing transient absorption spectroscopy. The obtained carrier dynamics reveal the reaction mechanism and indicate the change of the CdSe band position and hence driving force for charge transfer.
The Influence of Inverse Opal Template and Substrate Type on Electrodeposited 3D Macroporous Oxides
Authors: O'Hanlon Sally , McNulty David , O'Dwyer Colm 
Published: February 2020

The objective of this study is a detailed investigation into the preparation of V2O5 inverse opals using electrodeposition into preformed colloidal opal templates as a function of electrodeposition parameters (sphere size, voltage, time and substrate). Inverse opals have a range of applications(1-3) and many materials can now be formed into 3D macroporous IO structures.(4-6) Electrodeposition of a VOSO4 aqueous solution in to the inverse opal template is investigated on three different substrates; transparent conducting oxide glass, stainless steel, and thermally oxidized stainless steel. The electrodeposition follows a diffusion limited growth mode to form 3D porous crystalline V2O5 after removal of the colloid photonic crystal template of self-assembled polystyrene spheres. Inverse opals were grown using spheres ranging in diameter from 0.5 µm to 6 µm, and binary inverse opals are also electrodeposited using binary mixtures of sphere size. Analysis of the electrodeposition growth profiles show that IO growth in single and binary opal templates is diffusion limited and that pre-heating stainless steel forms an oxide coating that forces the initial current to increase to a steady state to overcome the resistive oxide, allowing IO to electrodeposit at relatively constant rate. Tortuosity is significantly increased when large sphere diameter templates are used, and especially pronounced when binary opal templates are used, because of interstitial void filling by small spheres in binary opal templates. Raman scattering and X-ray diffraction confirm phase pure, high crystalline quality V2O5 is generally formed in all cases (voltages and substrates). Electrodeposition ensures electrical interconnection within the 3D structured material by definition.

References

1. E. Armstrong and C. O'Dwyer, J. Mater. Chem. C, 3, 6109 (2015).
2. D. McNulty, H. Geaney, E. Armstrong and C. O'Dwyer, J. Mater. Chem. A, 4, 4448 (2016).
3. M. Osiak, H. Geaney, E. Armstrong and C. O'Dwyer, J. Mater. Chem. A, 2, 9433 (2014).
4. H. Liu, H.-M. Cho, Y. S. Meng and Q. Li, ACS Appl. Mater. Interfaces, 6, 9842 (2014).
5. S. J. Yeo, H. Kang, Y. H. Kim, S. Han and P. J. Yoo, ACS Appl. Mater. Interfaces, 4, 2107 (2012).
6. E. Armstrong, M. O'Sullivan, J. O'Connell, J. D. Holmes and C. O'Dwyer, J. Electrochem. Soc, 162, D605 (2015).
7. Y. Zhao, X. Li, J. Liu, C. Wang, Y. Zhao and G. Yue, ACS Appl. Mater. Interfaces (2016).
in-Situ Electrochemical-AFM and CV Measurement Study on the Nucleation and Growth in Reduced Graphene Oxide Electrode Contacts
Authors: Pyo Sung Gyu 
Published: February 2020

Electrochemical atomic force microscopy (EC-AFM) is a composite electrochemical analysis method. A lot of researches have been done on this, and it has been applied in many fields. EC-AFM was composed of EC-Cell, electrochemical analysis system, AFM and so on. For electrochemical analysis system and AFM to be analyzed at the same time, EC-Cell with a suitable structure is required. In this study, we made an electrochemical system in AFM with CV measurement system for in-situ observation of the elctrochemical reaction. Based on the developed EC-Cell, EC-AFM experiment system which was developed by constructing EC-AFM analysis system and numerical analysis method were proposed and tested and studied. First, we confirmed the EC-AFM analysis procedure and analysis method developed by observing copper electrochemical corrosion process. Second, electrochemical reduction characteristics of graphene oxide were studied using electrochemical analysis. An electrochemical atomic force microscope (EC-AFM) was used to study the reaction of wet electrode in various electrolyte, when the reaction corresponding to what occurs at the electrode of an electrode deposition. We observed wet plated solar electrode process during cyclic-voltammetry (CV) measurement with atomic force microscopy, and then were obtained useful continuous in situ images of the surface morphology. These AFM images dynamically showed the surface morphology change during the electro deposition. It was confirmed that initial nucleation of electrode crystals occurs after supersaturation, and that the slow dissolving on CV. AFM images of the electrode crystal morphology were compared with those in a different potential sweeping rate and electrolyte concentration at CV. We also compared the difference in AFM images and SEM images that were observed on the same electrode sample. Finally, we investigated the copper electrochemical deposition process in reduced graphene oxide using EC-AFM and observed the copper film formation process on reduced graphene oxide surface. As a result, the EC-AFM analysis system was constructed and tested, and the electrochemical characteristics on the reduce graphene oxide surface were observed.
Nafion Film Investigations Using Ferricyanide As a Probe Molecule
Authors: Reynolds Marissa Kayle , Paul David W 
Published: February 2020

Nafion membranes are a common choice in proton exchange membranes used in hydrogen-oxygen fuel cells. Their purpose is to separate the fuel and the oxidant within the cell, and allow protons from hydrogen oxidation to migrate through the Nafion membrane to the cathode. The electrons from the oxidation are thermodynamically pushed to the cathode through an external circuit where the current is driven through a load. One major issue with proton exchange membranes is their durability. Degradation can occur mechanically and chemically. In this work, a probe molecule, ferricyanide with hydrodynamic voltammetry was used to determine tears or imperfections in Nafion membranes cast over gold electrodes. Ferricyanide is negatively charged and therefore should not enter a Nafion membrane, any recorded red/ox signal indicates that the molecule has gained access to the bare electrode through an imperfection in the membrane. Hydrodynamic voltammetry was used to control the thickness of the solution diffusion layer thickness so that diffusion through the solution could be discriminated from diffusion processes in the membrane. During the work we also discovered, as others had, that negatively charged species1 and ferricyanide specifically2
can permeate into Nafion, albeit at a very slowly. This permeation rate is too slow to be recorded on the short time-scale of a hydrodynamic voltammetry experiment. However, if ferricyanide was included in the solution used to hydrate the membrane, a ferricyanide red/ox signal was seen indicating that approximately 0.4 mM had become trapped in the membrane (Figure 1). Moreover, only hydrated membranes containing ferricyanide, provide enough conductivity through the membrane to detect ferricyanide in solution (Figure 2). The signals obtained through these membranes were evaluated with a combination of the Koutecky-Levich equation3 and permeability equations from the Gough group4.
1. Unnikrishnan, E. K.; Kumar, S. D.; Maiti, B., Journal of Membrane Science
1997,
137, 133-137.
2. DeWulf, D.; Bard, A. J., J. Macromol. Sci., Chem.
1989,
A26 (8), 1205-9.
3. Bard, A. J.; Faulkner, L. R., Electrochemical Methods: Fundamentals and Applications. 1980; p 718 pp.
4. Gough, D. A.; Leypoldt, J. K., Analytical Chemistry
1979,
51 (3), 439-444.

Figure 1
Effects of Additives on the Electrodeposition of Nano-Grained Ni-Mo Alloys
Authors: Shi Y.N. , Hu J. , Zheng X.G. , Lu K. 
Published: February 2020

Nano-grained (ng) materials have attracted much interest in the past few decades, as these materials are expected to have superior properties to their coarse-grained counterparts. Nevertheless, owing to the large fraction of grain boundary, the grain boundary energy becomes so high with the grain size down to a few nanometers that it is challenging to synthesize ng metals with extremely fine grain size. One possible way to do this is to prepare ng alloys instead of pure ng metals by choosing appropriate alloy systems with a tendency of segregation, as the segregation of solute atoms at grain boundaries will reduce grain boundary energy and thus stabilize the nanostructure. Electrodeposition has been found very promising in synthesis of ng metals, where additives are usually introduced to reduce grain size by moving the onset deposit potential negatively and consequent increasing the nucleation rate. In the electrodeposition of ng alloys, however, it is to be explored the effect of additives to the composition and the grain size of the synthesized ng alloy.
It is the purpose of the present work to explore the effect of additives (saccharin and 1, 4-butynediol) in the synthesis of ng Ni-Mo alloy film in aqueous citrate-ammonia electrolyte with different concentration of sodium molybdate (Na2MoO4·H2O) ranging from 0.5 to 7 g/L. The chemical composition of ng deposits were determined by Energy-dispersive X-ray spectroscopy (EDS). The microstructure of the synthesized ng Ni-Mo films were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM) with the grain size determined by TEM dark field images. Voltammetry was employed to evaluate the effect of additives and also sodium molybdate to the deposition of Ni-Mo.
XRD results demonstrate that the as-deposited Ni-Mo films are all single fcc solid solutions. It is found Mo content in the deposits increases with the concentration of sodium molybdate in the electrolyte irrespective of the presence of additives. In addition, additives do not induce significant difference in the composition of the alloy deposits at a certain concentration of molybdate. The average grain size of the deposits decreases with the increase of sodium molybdate concentration from 44 nm to 5 nm corresponding to 0.5 g/L and 7g/L Na2MoO4·H2O respectively in plain solution, but the grain size reduces to 16 nm and 4 nm respectively in additives-added electrolyte corresponding to the same Na2MoO4·H2O concentration range. It is evident that saccharin and 1, 4-butynediol pronouncedly reduce the grain size of ng Ni-Mo when the Na2MoO4·H2O concentration is low but this reduction gradually gets small with the increase of molybdate concentration. Steady state polarization curves with the addition of additives and molybdate indicate an interaction between the saccharin, 1, 4-butynediol and the sodium molybdate, which correlates well with the composition and the characterized microstructure of ng Ni-Mo films.
Atom Probe Tomography of Dealloyed Materials
Authors: El-Zoka Ayman A. , Newman Roger C. , Langelier Brian 
Published: February 2020

The high resolution characterization of nanoporous gold (NPG), a material with promising functional capabilities, facilitates better understanding of its structure-property relationships. An improved characterization of NPG by atom probe tomography (APT) was recently reported, using Cu electroplating to fill the pores [1]. Atomic scale analysis of nanoligaments showed the expected core-shell structure in high detail (Figure 1), confirming and extending previous findings using other characterization methods [2].
Further to those findings, finer, more complex nanoporous materials, formed by dealloying of AgAuPt alloys, have been studied by APT as well as STEM tomography, demonstrating an ever clearer 3D picture of the structure. As the extent of aberrations found in the data is directly related to the relative evaporation fields of the metals in the sample [3], further improvement of this technique prompts the search for alternative metallic fillers.
Figure 1- (a) Atom map of a single nanoligament in NPG formed by dealloying of Ag77Au23, (b) Chemical profiling across a single ligament.

References

[1] Ayman A. El-Zoka., Doug D. Perovic, Roger C. Newman, and Brian Langelier. "High Resolution Studies of Dealloyed Layers." In Meeting Abstracts, The Electrochemical Society, vol. 12, pp. 1259-1259, 2016.
[2] T. Fujita, P. Guan, K. McKenna, X. Lang, A. Hirata, L. Zhang, T. Tokunaga, S. Arai, Y. Yamamoto, N. Tanaka, Y. Ishikawa, N. Asao, Y. Yamamoto, J. Erlebacher and M. Chen, "Atomic origins of the high catalytic activity of nanoporous gold," Nature Materials, vol. 11, pp. 775-780, 2012.
[3] T.T Tsong, “Field ion formation,” Surf. Sci., vol. 70, pp. 211-233, 1978.

Figure 1