bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Nanoelectronic Heterodyne Sensor: A New Electronic Sensing Paradigm
Authors: Zhong Zhaohui
Published: February 2020

Nearly all existing nanoelectronic sensors are based on charge detection, where molecular binding changes the charge density of the sensor and leads to sensing signal. However, there are several fundamental limitations to the charge-detection based electronic sensors. The examples include the ionic screening effect in high ionic strength solution, and the sensitivity-speed tradeoff for vapor phase sensing. In this talk, I will discuss our group’s recent works on a new paradigm of electronic sensing by exploring the heterodyne mixing response between the molecular dipole and a nanoscale transistor. First, we successfully demonstrated that the fundamental ionic screening effect can be mitigated by operating single-walled carbon nanotube field effect transistor as a high-frequency heterodyne biosensor. Electrical detection of streptavidin binding to biotin in 100 mM buffer solution is achieved at a frequency beyond 1 MHz. The results should promise a new biosensing platform for point-of-care detection, where biosensors functioning directly in physiologically relevant condition are desired. Second, we demonstrated the concept of nanoelectronic heterodyne sensor for vapor detection in a graphene device. The dipole detection mechanism is confirmed by a plethora of experiments with vapor molecules of various dipole moments, particularly, with cis- and trans-isomers that have different polarities. Rapid (down to 0.1 s) and sensitive (down to 1 ppb) detection of a wide range of vapor analytes is achieved, representing orders of magnitude improvement over state-of-the-art nanoelectronics sensors. Finally, we demonstrated electrical probing and tuning of the non-covalent physisorption of polar molecules on graphene surface by using graphene nanoelectronic heterodyne sensors. Our results provide insight into small molecule-nanomaterial interaction dynamics and signify the ability to electrically tailor interactions, which can lead to rational designs of complex chemical processes for catalysis and drug discovery.
(Invited) Self-Powered, Wireless Medical Sensor and Devices
Authors: Li Zhou
Published: February 2020

Implantable medical devices and integrated wireless healthcare sensors are attracting extensive attention, but the batteries used for powering these devices usually display a limited lifetime. Although battery technology has improved, sustainable power sources for cardiac pacemakers, neural stimulators and other implantable biomedical devices are required. Mechanical energy was considered as one of most abundant and accessible energy sources around the human body. When a small system can efficiently convert mechanical energy in our daily life, this system would be a suitable solution for electricity generation and significantly extend the lifetime of the electronic devices, especially in medical area.

Recently, triboelectric nanogenerator (TENG) has attracted much attention and been considered as another potential solution for harvesting mechanical energy. With its high output performance, outstanding biocompatibility and low cost, TENG has been studied for powering implantable medical electronic devices. Here, we demonstrated an in vivo biomechanical-energy harvesting using a TENG. An implantable triboelectric nanogenerator (iTENG) in a living animal has been developed to harvest energy from its periodic breathing. We also developing an encapsulation method for protecting iTENG from the contamination or liquid infiltration of the surrounding environment. Another important consideration is the versatility of the energy harvesters, which can facilitate the integration between iTENG and the various implantable medical electronics and promote the development of self-powered implantable medical devices and wearable/portable electronics. We also designed viable inner connections and universal outlet connectors for the system. The power management elements and NG were integrated on a flexible substrate; therefore, the entire system could be a “Plug and Play” mobile power source. The system was also packaged by PDMS as a waterproof implantable full energy unit for implantable medical electronic devices.

The energy generated from breathing and body moving was used to power a prototype pacemaker and a low-level laser cure (SPLC) system, respectively. It was found that the self-powered system could regulate the heart rate of a rat and significantly accelerated the mouse embryonic osteoblasts' proliferation and differentiation. This is a significant progress for fabricating self-powered implanted medical electronic devices using TENG as a power source.

Figure 1
Preparation of Highly Active Au/Pd Nanocatalysts for Self-Powered Sensing Applications
Authors: Chang Ting-Wei , Rao Yun-Ting , Lin Zong-Hong
Published: February 2020

Self-powered sensing systems that can work without external power sources have recently been demonstrated to detect pH, humidity, pressure, and temperature. By harvesting energy directly from the environment, these self-powered sensing systems are advantageous in minimizing the size, having long-term operation, and avoiding the use of toxic materials in battery. In this paper, we prepared Au/Pd nanomaterials as the nanocatalysts in the self-powered sensing systems. Au nanoparticles were synthesized first and served as the seeds for the growth of Pd component. The content of Pd component on the Au nanoparticles could be varied by reacting with different concentration of Pd2+ ions. Cyclic voltammetry indicated that the electrocatalytic oxidation of ethanol was dependent on the content of Pd component. Finally, we combined the as-prepared Au/Pd nanomaterials with a self-powered sensing system for ethanol detection. The self-powered ethanol sensor developed here could become a real sensing system in the futures.
(Invited) Growth of Vertically Aligned Piezoelectric Diphenylalanine Peptide Microrods for Energy Harvesting
Authors: Nguyen Vu , Jenkins Kory , Yang Rusen
Published: February 2020

Nanoscale energy harvester holds promise for the development of self-powered nanosystems, while molecular self-assembly of bio-inspired materials has attracted much research effort in recent years due to its potential to fabricate novel bottom-up structures for new applications. Among them diphenylalanine (FF) peptide has been widely explored recently. Strong piezoelectricity was demonstrated in FF peptide nanotubes. Here we report a new and scalable approach to the controlled fabrication on various substrates of vertically aligned FF peptide microrods with uniform polarization. Piezoelectric FF peptide microstructures were fabricated on various substrates through a novel epitaxial growth approach. We start by engineering a textured seed layer with preferential vertical orientation, and then grow the FF peptide microrods epitaxially from this seed layer. The low-temperature process produced vertically aligned FF peptide microrods with hexagonally arranged nanochannels and uniform polarization. Direct measurement of the piezoelectricity was achieved for the first time from a solid FF peptide single crystal and yielded an effective piezoelectric coefficient d33 at 9.9 pm/V. Our work can enable new applications of bio-inspired materials in areas such as energy harvesting and storage, electromechanical sensing and actuation, drug delivery, as well as fundamental studies of FF-based structures.
Development of Biocompatible Triboelectric Nanogenerators by Using Polypeptides As the Contact Materials
Authors: Chen Chuan-Hua , Tsao Yu-Hsiang , Lin Zong-Hong
Published: February 2020

Since the first invention of triboelectric nanogenerator in 2012, it has been developed into a new energy technology. Triboelectric nanogenerator has been applied to efficiently convert the mechanical vibration energy into electricity. The fundamental mechanism of triboelectric nanogenerators is based on the contact electrification and the electrostatic effect. Among these two effects, surface charges transfer happened during the contact electrification process is the main factor to affect the electric output of triboelectric nanogenerators. The electric output of most triboelectric nanogenerators would decrease in environments with high relative humidity, which restricts their application. By using polypeptides as contact materials to construct biocompatible triboelectric nanogenerators, we found that the electric output of the triboelectric nanogenerators can be maintained or is even enhanced at higher relative humidity.
Black Phosphorus: New Opportunities in Electronic Device Applications
Authors: Yin Demin , Yoon Youngki
Published: February 2020

Black phosphorus (BP) is one of layered materials drawing significant attentions in solid-state and electrochemical societies. BP has a direct bandgap, which can be tuned by varying the thickness of material or the number of layers. Due to its large carrier mobility, BP is considered as a promising contender for the future electronic device applications. However, designing field-effect transistors (FETs) based on BP is not straightforward since the relevant device physics can be significantly different from that of conventional metal-oxide-semiconductor (MOS) FETs based on 3D materials such as silicon or III-V semiconductors. Therefore, careful engineering practices are required to use BP for transistor applications. In this study, we will mainly discuss design strategies for conventional FET structures and tunnel FETs (TFETs) based on the novel layered material of BP. We perform self-consistent atomistic quantum transport simulations using non-equilibrium Green’s function (NEGF) formalism with tight-binding approximation. For high-performance device applications, conventional FET structure based on BP is considered. Our simulation results reveal that, among few-layer BPs, monolayer BP can provide the best device performance with the largest on current (~5 mA/μm), the largest on-off current ratio (~107), and the smallest subthreshold swing (62 mV/dec), showing three times larger on current and three orders of magnitude smaller off current compared to 2022 International Technology Roadmap for Semiconductors (ITRS). Although bilayer BP FETs also exhibit as comparable device performance as monolayer BP FETs, in general, thicker BP is not preferable mainly due to the worse gate electrostatic control, which affects the overall device performance negatively. Secondly, for low-power devices, BP is integrated into the lateral tunnel FET structure, where small off current and steep subthreshold slope are of great importance rather than on state characteristics. Our simulation results show bilayer and trilayer BP are preferable for TFETs applications, unlike the conventional FET structure, while monolayer BP suffers from small on current due to its large bandgap. By carefully engineering various device parameters, an ultra-high on-off current ratio (> 1011) and an extremely small subthreshold swing (~15 mV/dec) can be achieved in bilayer and trilayer BP TFETs, demonstrating the great potential of few-layer BP over monolayer. This study shows that BP FETs can be tuned for various target applications by engineering the material and device parameters properly.
Transport-Geometry Interactions in Li-Ion Cathode Materials Imaged Using X-Ray Nanotomograph
Authors: Nelson George J. , Ausderau Logan , Buckley Joseph , Mistry Aashutosh , Mukherjee Partha P. , De Andrade Vincent
Published: February 2020

Layered Li-transition metal oxide compounds of the form LiMO2 serve as chemically stable, energy dense active cathode materials for Li-ion batteries. Among these materials Li(Ni1/3Mn1/3Co1/3)O2 (NMC) has received increased attention due to its improved rate capability compared to other  LiMO2 cathode materials. Forging a stronger connection between complex mesoscale electrode geometry, material performance, and processing techniques can enable development of practical approaches for realizing electrode performance controlled by mesoscale geometry. To this end, 3D x-ray imaging, microstructural characterization, and computational modeling techniques have been applied to analyze the charge/discharge behavior of the active material in a set of NMC cathodes subject to varied processing approaches. For the present studies, the cathodes were produced using combinations of rapid or gradual drying process along with ball milling and calendaring prior to cutting into coin cell electrodes. Samples were extracted from pristine cathodes and imaged using x-ray nanotomography approximately halfway between the Co and Ni K-absorption edges. Imaging at this x-ray energy provided clear contrast between the NMC phase and the carbon/binder/pore regions within the samples. Particle geometry was characterized and compared for samples from four cathodes treated with distinct combinations of preparation steps. Geometric characteristics of the active cathode material include the particle size distribution, surface area, volume, and sphericity. Following characterization the tomographic data sets were applied as computational domains in multiphysics transport models to assess the effects of processing methodology on charge/discharge performance. Distinct variation in particle count and geometry is observed within the samples analyzed. The performance implications of this variation are discussed, particularly with respect to charge/discharge capabilities. A comparison is also made for particles with varied degrees of mechanical degradation.
Life Tests of Current Switched Oxygen Electrodes for Reversible Solid Oxide Cells
Authors: Railsback Justin , Hughes Gareth , Lu Matthew , Barnett Scott A
Published: February 2020

Large scale energy storage is a necessary component of any electricity grid operating primarily on intermittent renewable power sources. Recent experimental and techno-economic studies on reversible solid oxide cell (ReSOC) technology suggest that this technology performs well compared to other available technologies in terms of round-trip efficiency, stable storage time, and cost per kilowatt-hour stored.[S.H. Jensen, Energy Environ Sci 2015 ,8, 2471-2479] However, SOCs are known to degrade by delamination at the oxygen electrode under electrolysis conditions; this must be better understood in order to operate SOCs over their desired lifetimes.  Here we investigate the conditions that cause delamination and degradation by carrying out life tests of symmetric cells, observing electrochemical behavior by impedance spectroscopy and by post-test SEM analysis. Symmetric cells are subjected to switching current operation with a 12 hour period at current densities ranging from 0.5 to 2.0 A/cm2 – similar to that expected in a ReSOC energy storage application. Cells are typically operated for 1000 hours, long enough to detect degradation rates as low as 1 %/kh.  Three types of symmetric cells are investigated: single phase (La0.6Sr0.4)(Co0.2Fe0.8)O3 (LSCF) on Ce0.9Gd0.1O2 (GDC), (La0.8Sr0.2)MnO3 (LSM) on Zr0.92Y0.08O2 (YSZ) and La2NiO4 wet infiltrated into (La0.9Sr0.8)(Ga0.8Mg0.2)O3 (LNO infiltrated LSGM) on LSGM.  Degradation rates are determined for each current density and corresponding initial electrode overpotential. Degradation rates < 1%/kh are observed for LNO infiltrated LSGM on LSGM at 1.0 A/cm2 (0.20 V), and below ~0.9 A/cm2 (0.1 V) for LSCF on GDC.  The results are also compared with prior results from similar experiments with (La0.8Sr0.2)MnO3 (LSM) on Zr0.92Y0.08O2 (YSZ).  Changing the temperature by 50 °C from 800 to 750 °C for a previously stable current density (0.5 A/cm2) for LSM-YSZ results in a higher over potential (0.55 V) and fast degradation. Comparing the critical current densities and overpotentials where the degradation rates become measurable, and where structural damage can be observed in post-test SEM images, for this range of different electrode and electrolyte materials, suggests that degradation is controlled by overpotential rather than by current density.
Characterization of Ultra-Low Pt Loading Meas Prepared By Electrospray
Authors: Martinez-Vazquez Beatriz , Sanchez Daniel G , Martin Santiago , Castillo Jose Luis , Garcia-Ybarra Pedro Luis , Friedrich K. Andreas
Published: February 2020

Ultralow Pt-loading electrodes with 0.02 mgPt cm−2and 0.04 mgPt cm−2 were prepared by electro hydrodynamic atomization (electrospray) of catalytic inks on carbon paper coated with a carbon micro-porous layer. MEAs of 25 cm2 active area were manufactured with this type of electrodes [1-3] and tested in a single-cell equipped with segmented bipolar plates to show in operando the local current density distribution throughout the electrode surface. From hydrogen & air as feeding gases, tests under different pressures, relative humidity and gas flow rates were performed using the segmented cell [4,5]. Moreover, electrochemical impedance spectroscopy (EIS) analyses were accomplished to determine the ohmic and charge transfer resistances in each of the test conditions. The best performance was achieved for a MEA with an overall loading of 0.06 mgPt cm−2 providing a platinum utilization of 3.8 kW gPt
−1 at 0.6 V and a maximum platinum utilization of 5.9 kW gPt
−1 when working at 70 ºC, 1.5 bar and stoichiometries of λH2=1.5 and λair= 2, At different test conditions, i.e. increasing the backpressure or the feeding flow rate, the cell behaviour improves significantly and maximum platinum utilizations of 9 kW gPt
−1 and 7 kW gPt
−1 were respectively reached. Additionally, short-term runs of about 100 hours of continuous operation were carried out to assess electrode durability.

References

[1] S. Martin, P. L. Garcia-Ybarra, J. L. Castillo, Method for the Uniform  Nanostructured Deposition of Catalytic Particles by Means of Electrospray,  WIPO Patent PCT Application No. WO 2013/144390 A1.

[2] S. Martin, P. L. Garcia-Ybarra, J. L. Castillo, Electrospray deposition of catalyst layers with ultra-low Pt loadings for PEM fuel cells cathodes, J. Power Sources, 195  (2010) 2443–2449.

[3] S. Martin, B. Martinez-Vazquez, P. L. Garcia-Ybarra, J. L. Castillo, Peak utilization of catalyst with ultra-low Pt loaded PEM fuel cell electrodes prepared by the electrospray method, J. Power Sources, 229 (2013) 179–184.

[4] B. Martinez-Vazquez, D. G. Sanchez, J. L. Castillo, K. A. Friedrich, P. L. Garcia-Ybarra, Scaling-up and characterization of ultralow-loading MEAs made up by electrospray, Int. J. Hydrogen Energy, 40 (2015) 5384-5389

[5] M. Schulze, E. Gülzow, S. Schönbauer, T. Knöri, R. Reissner, Segmented cells as tool for development of fuel cells and error prevention/prediagnostic in fuel cell stacks, J. Power Sources, 173  (2007) 19–27.
(Invited) 2-D Surface Phases for Energy-Related Applications
Authors: Luo Jian
Published: February 2020

Nanoscale, impurity-based, surficial films with self-selecting or “equilibrium” thickness can form spontaneously as the thermodynamic equilibrium states in various oxide materials [Annu. Rev. Mater. Res. 38: 227 (2008)]. They can be considered as a unique class of 2-D surface phases (that are also called “complexions” to differentiate them from the 3-D bulk phases defined by Gibbs). Such surface phases can be utilized as a class of ideal nanocoatings (made by thermodynamics) to improve the performance of various functional materials for energy-related applications. This presentation will review a series of our recent studies to utilize this and other analogous types of spontaneously-formed 2-D surface phases to tailor battery cathode [APL 95: 211905 (2009); JCCP 16: 7786 (2014)] and anode [J. Power Source 245: 594 (2014)] materials, supported oxide catalysts [APL 91: 061909 (2007); Acta Mater. 56: 4702 (2008)] and photocatalysts [Mater. Lett. 98: 205 (2013)], nanowire-based fast oxygen-ion conductors [Nature Communications 6: 8354 (2015)], and supercapacitors [unpublished results]. A potentially-transformative scientific goal is to utilize such 2-D surface phases to achieve superior properties that are unattainable by conventional bulk phases.
Electrochemical Charge Storage in Hierarchical Carbon Manifolds
Authors: Narayanan Rajaram , Vijwani Hema , Mukhopadhyay Sharmila Mitra , Bandaru Prabhakar R
Published: February 2020

The use of hierarchical assemblies constituted from macroporous structures (e.g., reticulated vitreous carbon, RVC) where the internal pore area is covered with closely spaced nanostructures (e.g., carbon nanotubes, CNT) is proposed for substantially enhancing the energy density of electrochemical capacitors, while maintaining large charge/discharge rates. While the macroscale pores enable storage of substantial electrolyte volumes that would contribute through redox reactions to the energy density, the closely spaced nanostructures provide a large geometric area and capacitance in addition to enabling rate independent Faradaic charge storage via thin layer electrochemistry (TLE). A fifty fold increase in the double layer capacitance, in addition to increased Faradaic charge density – with potential for orders of magnitude improvement, was observed for the RVC-CNT electrodes, in comparison to the bare RVC foam electrode. It was seen that the hierarchical assembly enables the contribution from ~ 94% of the net volume of the wetted RVC-CNT electrode for active Faradaic charge storage.
Characterizing Bioconjugated Nanoparticles By Nano-Impact Electrochemistry
Authors: Karimi Anahita , Hayat Akhtar , Andreescu Silvana
Published: February 2020

Bioconjugated nanoparticles that combine the selectivity of biomolecules with the unique properties of nanoparticles have received a great deal of interest for applications in biomedicine, biosensing and biotechnology. While widely used, evaluation and characterization of immobilized biomolecules on the surface of nanoparticles remain a challenge. In this presentation, we describe the use of nano-impact electrochemistry as a novel technique for characterizing biomolecule-nanoparticle conjugation. The method can be used to quantitatively investigate biomolecular recognition and bioconjugation with a high degree of sensitivity and in the absence of exogenous reagents.
Local pH Determines Lanthanum Accumulation on Electrodes in Aqueous Solution
Authors: Babauta Jerome T. , Medina Adan , Beyenal Haluk
Published: February 2020

Electrochemical detection or accumulation of lanthanum and the lanthanides are typically investigated on modified electrodes such as carbon paste and mercury film electrodes.1-4 However, little data exists on lanthanum’s interaction with unmodified electrodes. Lanthanum deposition was characterized using an electrochemical quartz crystal microbalance (eQCM) in aqueous solution on unmodified carbon electrodes. We used a home-made pH microelectrode to directly measure a 10 pH unit variation in the local pH ~ 100 µm above a flat carbon electrode. The eQCM frequency response during voltammetric sweeps in the presence of lanthanum showed that the background current masked the dependence of lanthanum deposition on local pH and applied electrode potential. Lanthanum deposition in unbuffered LiCl solutions exhibited a stable deposited film until the anodic scan reached nearly 1.8 VAg/AgCl. The addition of 1 mM α-hydroxyisobutyric acid, a complexing ligand, decreased the deposition onset potential on the first scan. Subsequent scans showed the frequency response returning to that without added HIBA. Similar experiments with acetate-buffered solutions resulted in film stripping at -2VAg/AgCl on the anodic scan. The large variation in local pH is likely due to water electrolysis at the surface of the working electrode, which can impact form of the electroactive species. The formation of insoluble lanthanum hydroxides at high pH values contributes to the stable film in pH-controlled anodic sweeps. The frequency response on gold electrodes is also shown.

Refernces:

1.         P. D. Schumacher, J. L. Doyle, J. O. Schenk and S. B. Clark, Rev. Anal. Chem., 2013, 32, 159-171.

2.         P. D. Schumacher, K. A. Fitzgerald, J. O. Schenk and S. B. Clark, Anal. Chem., 2011, 83, 1388-1393.

3.         P. D. Schumacher, N. A. Woods, J. L. Doyle, J. O. Schenk and S. B. Clark, Anal. Chem., 2011, 83, 4788-4793.

4.         P. D. Schumacher, N. A. Woods, J. O. Schenk and S. B. Clark, Anal. Chem., 2010, 82, 5663-5668.
3D-Polypyrrole Hydro-Sponge Thin Films for Electrochemical Applications
Authors: Antonio Jadielson Lucas da Silva , Cordoba de Torresi Susana I. , Torresi Roberto M.
Published: February 2020

Conducting polymers have been targeted as research interest in many publications and it is possible to find applications in drug delivery systems, artificial muscles, artificial neurons, tissue engineering, supercapacitors, etc.  All this interest about conducting polymers comes from their unique properties such as, high conductivity, chemical stability, versatility and biocompatibility. At the present moment, not only the properties of the materials are important but also the ability to control their morphology is a goal, because this can lead to the improvement of the materials to be applied in different technologies. This work reports the controlled electrochemical synthesis of polypyrrole hydro-sponges (Ppy-HS) thin films nanostructured with methyl orange (MO) template.

The Ppy-HS thin film was synthesized on a gold surface using chronoamperometry. The synthesis was performed in 5 mmol L-1 MO aqueous solution to which 35 μL of distilled pyrrole (Py) were added to a final volume of 10 mL. The pH of the solution was adjusted to 2 by the addition of HCl. A three electrodes system was mounted using gold, Ag/AgCl/NaCl-3M electrode and platinum as work, reference and auxiliary electrodes, respectively. Different Ppy-HS thin films were synthesized at 0.6 V using different electrochemical charge of polymerization.

Scanning Electron Microscopy (SEM) characterization showed that the Ppy-HS presents a microfibrillar structure organized as a 3D material. However, it is possible to control the morphology of the Ppy-HS by the electrochemical charge of polymerization. Under the microfibrillar there is a compact layer with the typical granular structure of Ppy. After that, the increase of the electrochemical charge used in the polymerization results in the increase of the density of the microtubules to form a 3D structure.

The 3D porous structure makes the Ppy-HS a very interesting material for many technological applications. The material presents good elastic properties, high water uptake, and enhanced electroactivity. All these characteristics allows the application of PPy-HS in biosensors, drug delivery, tissue engineering and in other areas. In this work, the Ppy-HS is being explored in storage energy field. This material shows a specific capacitance of 800 F/g, which is much higher compared with no-strucutured Ppy and comparable to other materials applied in the field.

References:

Daí, T.; Lu, Y. J. Mat. Chem. 2007, 17, 4797.

Antonio, J. L. S.; Lira, L. M.; Gonçales, V. R.; Córdoba de Torresi, S. I. Electrochim. Acta 2013, 101, 216.
Experimental Study and CFD Model for Partial Oxidation of Methane over Self-Sustained Electrochemical Promotion Catalyst
Authors: Zhou Xiangyang , Huang Hao , Liu Hongtan
Published: February 2020

The so-called self-sustained electrochemical promotion catalyst or SSEP catalyst is a micro-particulate material with solid-solid interfaces between the active catalyst phase, the oxygen ion conductor, and oxygen reduction phase forming multiple micro-electrochemical cells. We have demonstrated that electrochemical promotion can make the catalyst more effective than conventional transition metal (Ni, Co) based catalysts and precious metal based catalyst for partial oxidation (POX) reforming of hydrocarbons. A computational fluid dynamics (CFD) model will help quantify the effects of the components in the microscopic electrochemical cells and of detailed thermal-chemical processes on electrochemical promotion thereby allowing better understanding and further optimization of the catalyst system.

A multi-physical multi-scale CFD was developed for analyzing POX of methane (CH4) over a SSEP catalyst in a fixed-bed reformer. The model incorporates a conventional transport processes, heat transfer, and kinetics for POX of CH4 over the active components and the electrochemical processes occurring in the unique microstructure. The simulation results show that the temperature in the first reactor with the Ni based conventional catalyst is generally about 30 K lower than that in the second reactor with the Ni-based SSEP catalyst. This temperature difference is impossible to explain the huge difference in the conversion in these two reactors.  The simulation results are compared with the experimental results. The good agreement can only be achieved by correctly describing the electrochemical processes and electrochemical promotion in the theoretical system. The validated model was used to predict the performance of the SSEP catalysts as a function of flow rate, O/C ratio, and the microstructure of the catalysts providing guidance for further optimization the SSEP catalyst.
Size, Chemical State, and Reactivity Correlations during the Electrochemical Oxidation of 2-Propanol over Au Nanoparticle Catalysts
Authors: Choi Yong-Wook , Sinev Ilya , Mistry Hemma , Zegkinoglou Ioannis , Roldan Beatriz
Published: February 2020

Numerous studies have been devoted to uncovering how the properties of nanoparticles (NPs), such as size, shape, chemical state and interaction with the support, affect their catalytic activity. To investigate the correlation among structure, oxidation state, and electrocatalytic activity, Au NPs with narrow size distributions (1 to 10 nm) were prepared via inverse micelle encapsulation by utilizing polystyrene-b-2-vinylpyridine block copolymers. The encapsulated nanoclusters were deposited onto conducting substrates and oxygen plasma etching was used to remove the residual polymeric ligands. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray absorption spectroscopy (XANES/EXAFS) were employed to characterize dynamic changes in the structure and chemical state of the NPs ex situ and under operando conditions. Results from these studies for the 2-propanol electrochemical oxidation under alkaline media over Au nanoparticles showed that a size-dependent trend was observed, with increasing activity (increased current density and lower overpotential) with decreasing NP size. Moreover, an enhanced endurance against poisoning by the acetone intermediate was also obtained for small NP catalysts. The insight into the dynamic evolution of the chemical state and NP structure was verified by operando X-ray absorption fine-structure (XAFS) measurements. It also cast light on the phenomenon of catalyst deactivation and the nature of the catalytically active sites.

Figure 1
Synthesis of Reduced Graphene Oxide-Supported PtAu Catalysts and Their Electrocatalytic Activity for Formic Acid Oxidation
Authors: Jeevagan Arockiam John , Gunji Takao , Tanabe Toyokazu , Kaneko Shingo , Matsumoto Futoshi
Published: February 2020

In this paper, we demonstrate that, a one-pot synthesis of a reduced graphene oxide (RGO)-supported freely assembled binary alloy catalyst (PtAu/RGO) under alkaline conditions. The synthesized PtAu/RGO catalyst has been characterized by powder X-ray diffraction (pXRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). It was found that graphene oxide (GO) was successfully reduced to RGO and that the PtAu nanoparticles exhibited alloy structure about 3.60 ± 0.20 nm in diameter and uniformly distributed on RGO surface. Further, the electrocatalytic activity of the catalyst was examined toward formic acid (FA) oxidation, which exhibited better catalytic activity toward FA

The electrocatalytic activity of PtAu/RGO (Pt mass loading: 20%) was examined with the solution of 0.1 M H2SO4 + 0.5 M HCOOH. The catalytic activity of PtAu/RGO was compared with the Pt/RGO (Pt mass loading: 20%) and commercial Pt/CB (Pt mass loading: 20%). Figure 1 shows that the linear sweep voltammograms of (a) Pt/RGO, (b) PtAu/RGO and (c) Pt/CB in 0.5 M HCOOH containing 0.1 M H2SO4 aqueous solution. It could be observed from the Fig. 5, two oxidation peaks can be clearly observed, the peak I is related to the direct oxidation of HCOOH to CO2, whereas the peak II is correspond to the oxidation of the COads generated from the dissociative adsorption step. The peak I current densities are in the order of PtAu/RGO > Pt/RGO > commercial Pt/CB, which indicates that the RGO can effectively enhance the activity of PtAu and Pt catalysts, which may be due to the strong interaction between PtAu or Pt NPs and RGO surface. In contrast, the peak II current densities are in the order of PtAu/RGO < Pt/RGO < commercial Pt/CB, indicating that the presence of RGO in PtAu/RGO hold back the formation of poisoning intermediate COadsduring the FA oxidation. Based on the present and previously reported results, it can be considered that the uniform distribution of NPs and electronic interaction between PtAu NPs and RGO could enhance the catalytic activity.

To sum up, freely assembled PtAu/RGO nanocomposites were synthesized under alkaline conditions. On the basis of pXRD, TEM, STEM, XPS, the GO was converted to RGO and PtAu NPs were highly dispersed and uniformly distributed through out the surface. The PtAu/RGO catalyst exhibited higher catalytic activity for FA oxidation compared to the other catalysts Pt/RGO and commercial Pt/CB. This work provides a simple and fast approach to synthesize a novel RGO based catalyst with high electrocatalytic activity.  

Figure 1. Linear sweep voltammograms of (a) Pt/RGO, (b) PtAu/RGO and (c) Pt/CB in 0.5 M HCOOH containing Ar-saturated 0.1 M H2SO4 aqueous solution at 2000 rpm.

Figure 1
Platinum Deposited on Carbon with Different Surface Properties for PEFC Application
Authors: Hayashi Akari , Noda Zhiyun , Sasaki Kazunari
Published: February 2020

Electrocatalysts for PEFC, made of platinum deposited carbon materials, have an import role to govern PEFC performance. The surface properties of carbon materials influence on both PEFC performance and durability. Especially, considering stop/start cycles of fuel cell vehicles, carbon oxidation becomes a serious problem since the potential at the cathode becomes as high as 1.5 V vs RHE. Durability against carbon oxidation is mostly determined by surface properties of carbon.

In this study, Vulcan XC72, which is a common carbon black support, is used, and its surface properties are controlled by heat treatments. Oxygen reduction reaction activity and durability were evaluated for platinum on surface controlled carbon, electrochemically. Additionally, we introduce our method to accelerate degradation of electrocatalysts using Environmental TEM (Hitachi HF-3300). For carbon oxidation, the air is introduced into the specimen chamber, and the specimen holder is heated up to 200 oC to accelerate degradation instead of cycling to high potential many times.

Regarding to the temperature of heat treatments, 1600 oC worked best in our studies. The surface of carbon black particles was graphitized, and a few graphitic layers were observed in TEM images. Oxygen reduction reaction activity was not much changed by the heat treatment, but the durability was significantly increased.

In order to understand the degradation mechanism on different carbon surface, the method using Environmental TEM was introduced. A new phenomenon of platinum particles embedded into Vulcan carbon with almost no agglomeration was observed. However, on graphitized Vulcan carbon surface, agglomeration more occurred, and embedding of platinum was rather suppressed. Since platinum on graphitized carbon showed much improved durability though the electrochemical analysis, embedding is believed to be a more predominate factor than agglomeration on degradation of PEFC performance.

Reference: X. Zhao, A. Hayashi, Z. Noda, K. Kimijima, I. Yagi, K. Sasaki, Electrochim. Acta 97 (2013) 33.
Two-Dimensional Ni(OH)2@Pt Nanosheets: High Activity Fuel Cell Oxygen Reduction Reaction Electrocatalysts
Authors: Rhodes Christopher , Godinez-Salomon Fernando
Published: February 2020

Oxygen reduction reaction (ORR) electrocatalysts with high activity, extended durability and lower cost are needed for proton exchange membrane fuel cells (PEMFCs). Compared with conventional nanoparticles, nanosheets composed of atomic-thin two-dimensional (2D) layers offer a higher relative concentration of catalytically active (111) surfaces.  In contrast to many approaches that have investigated graphene-supported Pt ORR catalysts, we have explored Pt supported on Ni(OH)2  nanosheets (i.e. Ni(OH)2@Pt) for enabling high activity ORR electrocatalysts.  Synthesis conditions were controlled to obtain Ni(OH)2  nanosheets with controlled sizes, phase, and aggregation.  Temperature/atmosphere treatments were found to significantly affect the structure and morphology of the nanosheets.  The effect of changing the Pt shell composition on the Ni(OH)2 nanosheets on the ORR activity was evaluated. The nanosheet structure and morphology with determined using x-ray diffraction and scanning electron microscopy, and the ORR activity was determined from rotating disc electrode experiments.  Our initial results have shown that Ni(OH)2@Pt nanosheets provide significantly higher catalytic activities compared with Pt/C. The ability to control the structure and properties of 2D transition metal oxide nanosheets provides a route to develop electrocatalysts with high activity, extended durability, and lower cost.
Role of Superoxide Anion in the Oxygen Reduction Reaction in Non-Aqueous Electrolytes with a Proton or Lithium Source
Authors: Zhang Yelong , Zhang Xinmin , Wang Jiawei , Chen Yuhui , McKee William C. , Bruce Peter G. , Xu Ye , Peng Zhangquan
Published: February 2020

The non-aqueous Li-air (O2) battery has generated a great deal of research interest because it potentially possesses far greater gravimetric energy storage density than today’s rechargeable battery technologies.1-4  Presently non-aqueous Li-O2 batteries suffer from irreversible reactions, including those due to impurities such as residual protons and proton-containing compounds that can react with reduced oxygen species.  To eliminate or alleviate the undesired reactions, it is crucial to have a fundamental understanding of the reactive oxygen species involved in the oxygen reduction reaction (ORR). 

In this talk we will present the results of a series of electrochemical studies of the ORR on a gold electrode in non-aqueous dimethyl sulfoxide (DMSO) electrolytes containing a proton or lithium source with TBAClO4 as supporting ions.  The superoxide anion (O2
-), the one-electron reduction product of O2, is identified in situ spectroscopically in both systems.  When the DMSO contains phenol as the proton source, O2
-, not HO2, appears as the first stable intermediate during the ORR upon cathodic scans, with H2O2 co-appearing at high overpotentials.5  When instead LiClO4 is added to DMSO, again O2
- is the first reaction intermediate to be detected, whereas surface LiO2 does not appear until the potential is much more negative of the Li2O2 formation potential.  The stability of O2
- vs. the other reduced O2 species is rationalized based on first-principles theoretical modelling and calculations.  Our studies show that the ORR mechanism depends intimately on the electrode potential and electrolyte composition, and contribute new mechanistic understanding for this reaction that is of fundamental importance to electrochemical energy storage and conversion technologies.

1. P.G. Bruce, S.A. Freunberger, L.J. Hardwick, J.-M. Tarascon, Nat. Mater. 2012, 11, 19.

2. J. Lu, L. Li, J.-B. Park, Y.-K. Sun, F. Wu, K. Amine, Chem. Rev.
2014, 114, 5611.

3. A.C. Luntz, B.D. McCloskey, Chem. Rev.
2014
, 114, 11721.

4. R. Black, B. Adams, L.F. Nazar, Adv. Energy Mater.
2012, 2, 801

5. Z. Peng, Y. Chen, P.G. Bruce, Y. Xu, Angew. Chem. Int. Ed.
2015, 54, 8165.
The Peformance of Nano Urchin-like NiCo2O4 Modified Activated Carbon As Air Cathode for Microbial Fuel Cell
Authors: Li Kexun , Ge Baochao
Published: February 2020

A nano urchin-like NiCo2O4 has been successfully synthesized via a facile and scalable hydrothermal method. A NiCo2O4 modified active carbon air cathode was designed, optimized and fabricated. The maximum power density of the microbial fuel cell with newly developed cathode is 2.28 time higher than bare active carbon and is comparable to the commercial available Pt/C, reaching 1730 ± 14 mW m-2. The modified active carbon showed remarkable improvement in activity towards the oxygen reduction reaction, which was due to the lower charger transfer, lower activation barrier, and higher exchange current density. Electrochemical evaluation showed a direct four-electron the oxygen reduction reaction on NiCo2O4 modified active carbon, compared to a two-stage process on bare active carbon. The non-precious NiCo2O4 could be considered as a promising alternative to the costly Pt.
Hollow-Spherical Co/N-C Nanoparticles Doped Activated Carbon Used As Efficient Electrocatalysts in Microbial Fuel Cell
Authors: Yang Tingting , Li Kexun
Published: February 2020

For the first time, the hollow-spherical Co/N-C nanoparticles doped in activated carbon was used in air-cathode microbial fuel cells (MFCs). Hereof, the Co/N-C nanoparticles, which combines the advantageous features of high surface area, sufficient active sites and high degree of graphitization, had been synthesized via a simple hydrothermal reaction followed by heat treatment. As a result, the Co/N-C showed superior catalytic activity, lower internal resistance, excellent kinetic activity towards oxygen reduction reaction (ORR) in MFCs. The maximum power density of MFCs with 10%Co/N-C air cathode was as high as 2514 ± 59 mW m2, almost 174% higher than the control. Therefore, it can be expected that the as-synthesized Co/N-C, with extraordinary electro-catalytic performance towards ORR comparable to commercial Pt/C, will be a promising alternative to the state-of-the-art non-precious metal ORR electro-catalysts for electrochemical energy applications.
Solar Hydrogen Production from Seawater Vapor Electrolysis
Authors: Kumari Sudesh , White Robert , Spurgeon Joshua M
Published: February 2020

Solar photovoltaic utilities require large land areas to produce power equivalent to a conventional fossil fuel utility, and also must be coupled to cost-effective energy storage to overcome the intermittency of sunlight and provide reliable, continuous energy generation. To target both of these disadvantages, a method was demonstrated to produce hydrogen fuel from solar energy by splitting seawater vapor from ambient humidity at near-surface ocean conditions. Using a proton exchange membrane electrolyzer with seawater-humidified air at 80% relative humidity at the anode and dry N2 at the cathode, sufficient electrolysis current density was maintained to operate near the maximum energy-conversion point when driven by a triple-junction amorphous Si solar cell of equivalent area. Fluctuations in atmospheric water content were demonstrated to have minimal effect on the solar-to-hydrogen efficiency, remaining ~ 6% with relative humidity ≥ 30%. Direct solar-driven H2 production from seawater vapor was maintained at > 4.5 mA cm-2 for > 90 hours. The calculated solar-to-hydrogen conversion efficiency before and after 50 h of operation changed from 6.0% to 6.3% using an ambient seawater humidity feedstock as compared to a drop from 6.6% to 0.5% using liquid seawater feedstock.
Strategy for the Incorporation of Light Absorbing Catalysts into Photoelectrochemical Devices
Authors: Suter Silvan , Haussener Sophia
Published: February 2020

Photoelectrochemical devices incorporate light absorbing semiconductors, reaction-selective and supporting catalysts, conducting and protecting interlayers, and ion-conducting electrolytes. The overall device performance is a complex interplay between the design and the performance of the individual components. Catalysts and photoabsorber are usually in immediate vicinity in order to minimize the transport lengths of the charge carriers. Nevertheless, a large number of catalysts are light absorbing and considerably reduce the amount of radiation accessible to the photoabsorber. We present and experimentally demonstrate a strategy allowing for the use of light absorbing catalysts in immediate vicinity of the photoabsorber with limited influence on device performance. The strategy was predicted using PEC device modeling and consists of the directed and limited application of catalysts on the photoabsorber in regions with high concentration of charge carriers. We show that parameters such as the catalyst performance, interlayer conductivity, electrolyte conductivity, and device design, are affecting the success of the strategy and provide general design guidelines for the incorporation of light absorbing catalysts into photoelectrochemical devices.

Figure 1
(Invited) Development of Semiconductor Quantum Dots and Their Interfacial Dynamics for Solar Energy Conversion
Authors: Tachibana Yasuhiro
Published: February 2020

Semiconductor quantum dots (QD) have received considerable interest as a novel material in solar energy conversion devices. The attractive property of these dots is known as “quantum size effect”, where the band gap energy becomes larger by reducing QD size. By employing this concept, the light absorption wavelength range can be tuned by controlling the QD size. In addition to this effect, by selecting appropriate elements, the light absorption range can be selected from UV or visible to near infrared region. This wavelength tunability is particularly attractive to designing a photocatalytic device such as solar water splitting, hydrogen generation or CO2 fixation devices.

The potential energy levels of the QD conduction and valence bands can also be adjusted with the QD size. An appropriate size will be selected to optimize efficient photo-induced charge separation and to retard charge recombination at the QD interfaces (Optimum Gibbs free energy difference), thereby facilitating performance improvement of solar energy conversion devices.

We are also interested in elucidating mechanisms of photocatalytic reactions at semiconductor interfaces. In particular, identification of interfacial reaction rates would be useful to design appropriate structures and selection of nanomaterials.

In this presentation, we will show some designs of synthesizing semiconductor quantum dots. Also, some examples of identifying interfacial dynamics employing time-resolved laser spectroscopies will be presented.

This work was financially supported by JST PRESTO program, Japan. The author also acknowledges Australian Research Council (ARC) LIEF grant (LE140100104) and the Office for University-Industry Collaboration, Osaka University, for the financial supports.