bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Translating Paper-Based Diagnostic Devices into Clinically Relevant Applications
Authors: Cheng Chao-Min
Published: February 2020

Developing methods to answer scientific questions is one of the practical approaches for doing science; optical microscopy, for example, has been a fundamental method of biological or medical discovery for more than three centuries. Building systems or tools to solve current issues existed in the world (e.g., infectious or chronic diseases) is also one of the attracting projects that we can involve and contribute. Due to this reason, for last few years, we have developed multiple “simple” technologies, which can be used in both developing and developed worlds. I will talk about what we are currently working on at National Tsing Hua University, including paper-based ELISA for the diagnosis of various diseases such as proliferative diabetic retinopathy, and other fiber-based diagnostic formats (i.e., cotton and bamboo), with their clinical validations, for clinically relevant diagnostic applications (septicemia and rapid diagnosis for organophosphorus and paraquat poisoning) in different divisions of medicine.
Shark Skin Inspired Riblet Microstructures As a Novel Solid-Liquid Triboelectric Nanogenerator for Energy Harvesting
Authors: Yeh CHENG , Liu Chia-Chen , Lin Zong-Hong
Published: February 2020

Nature has provided a number of innovative inspirations for human beings to design artificial systems in order to mimic the excellent performance of existing biological systems. One of the most important and unexplored example in this regard is the shark skin. The surface of the shark skin consists of a three-dimensional rib pattern which displays exceptional super-hydrophobicity effect and drag reduction effect compared to the absolutely smooth skin textures. Inspired by this characteristic feature found in nature, a novel triboelectric nanogenerator (TENG) has been developed for harvesting electrical energy arising from the solid-liquid interface. By integrating the shark-skin patterns with polytetrafluoroethylene (PTFE), the as-fabricated biomimetic surface exhibits excellent super-hydrophobicity. Moreover, the presence of the shark skin structures on the surface potentially enlarges the contact area thus inducing better intimate contact and reducing the effect of residual liquid on the triboelectric output. Owing to the aforementioned facts, our bio-inspired TENG would generate more accurate signals and thereby be a new paradigm for wider range of applications.
(Invited) scavenging of Mechanical Energy Using Piezoelectric and Triboelectric Materials
Authors: Lee Minbaek
Published: February 2020

The issue of the research for self-powered nanosystems is likely to integrate different nano-devices into a stand-alone. Such nanosystem, surely, requires a sustainable power source to make the entire package as self-powered one. In this regard, scavenging energy from the environmental sources can be a possible choice for powering nano-systems. Among the others, there are many of mechanical form of energy (such as body movement, muscle stretching) or vibration energy (such as acoustic/ultrasonic wave) which can be converted into electric energy. In here, we have demonstrated some approaches for converting mechanical energy into electric energy by piezoelectric, ferroelectric nanomaterials and triboelectric nanostructures. The technology allowed us to harvest energy which is mostly regarded as wasted mechanical movement/vibration or noises. Moreover, new design of devices have been fabricated, and possible materials for such generators have been explored. The presentation will be continuously dedicated to recent developments and improvements of energy harvesting technology towards self-powered nano-systems.
(Invited) Scalably-Nanomanufactured 2-D Tellurene for Ubiquitous Electronics and Smart Sensors
Authors: Wu Wenzhuo
Published: February 2020

The reliable production of two-dimensional (2D) crystals is essential for exploring new science and implementing novel technologies in the 2D limit. However, ongoing efforts are limited by the vague potential in scaling-up, restrictions on growth substrates and conditions, small sizes and/or instability of synthesized materials. In this talk, I will discuss our recent progress in the fabrication of large-area, high-quality 2D material by a substrate-free solution process. The crystals exhibit process-tunable thicknesses from a monolayer, bi-layer, tri-layer to tens of nanometers, and lateral sizes ~ 100 mm. Our prototypical 2D transistor device, which is air-stable, shows an excellent all-around figure of merits compared to existing 2D materials. We further carry out the first experimental exploration of piezotronic effect in such solution-grown 2D material and systematically investigate the piezotronic transport properties. The coupling between the piezoelectric and semiconductor properties in such material system enables the design and implementation of novel electronic devices and smart sensors that can interact with the mechanical stimuli. Our approach has the potential to produce stable, high-quality, ultrathin semiconductors with a good control of composition, structure, and dimensions for applications in electronics, optoelectronics, and energy devices.
(Invited) Surface Plasmon Resonance-Based Biosensing and Precision Medicine
Authors: Wu Nianqiang
Published: February 2020

First, this talk shows how to engineer plasmonic nanostructures to tune the optical properties and localized electromagnetic field. Second, this talk reveals how to use plasmonic nanostructures to construct surface-enhanced Raman scattering (SERS) sensors for disease biomarker detection. Third, this presentation demonstrates how to use plasmonic nanostructures for photodynamic therapy of tumor.
Highly Sensitive Solid-Liquid Interfacing Triboelectric Nanosensor for Self-Powered Mercury Ion Detection
Authors: Chen Shuo-Wen , Lin Yu-Jhen , Lin Zong-Hong
Published: February 2020

Till date, the potential of the solid-liquid triboelectric nanosensor for chemical sensing applications have remained unexplored. In this work, the first self-powered nanosensor based on solid-liquid triboelectric effect for the detection of mercury ions is substantiated. The triboelectric nanosensor was designed by using tellurium nanowires as the solid triboelectric layer and deionized water as the liquid triboelectric layer. Owing to the highly specific reaction between tellurium and mercury ions, the as-developed triboelectric nanosensor have proved to be highly selective and thereby have the capability to distinguish even small traces of mercury ions in complex environmental samples. The triboelectric nanosensor can offer a detection range of 10 nM-10 mM toward mercury ions. Moreover, hydrophilic and hydrophobic tellurium nanowires were synthesized to evaluate the effect of surface properties on the efficiency of triboelectric nanosensor. Based on the results, it is believed that solid-liquid triboelectric effect will be a new and efficient tool for the designing of rapid, portable and low-cost chemical nanosensors.
(Invited) Bio-Lasers: An Emerging Field Bridging Laser Photonics and Biomedicine
Authors: Chen Yu-Cheng
Published: February 2020

Bio-lasers are emerging technology for next generation biochemical detection and biophotonic applications. Recently, laser-based detection has been exploited as a novel tool in biosensing due to their capability to amplify subtle changes in the gain media caused by underlying biological processes. Laser emission has unique merits over fluorescence, including threshold-gated emission, narrow linewidth, and strong intensity, leading to ultrasensitive detection of intracellular dynamics, and superior contrast for higher spectral/spatial resolution imaging. In this talk, I will introduce the recent advances of biolasers in cells, tissues, and neuronal networks, by using several types of micro-laser cavities, such as optofluidic ring resonators and high-Q Fabry-Pérot mirrors. Next, we demonstrate the possible implementation of biolasers into an automated lasing system for systematic and statistical analysis, including an integrated cellular laser array device and laser-emission microscopy for cancer screening and immuno-diagnosis. Furthermore, optical recording of calcium transients during spontaneous neuronal activities was first demonstrated via neuron lasers with a significantly improved sensitivity, not only for monitoring neuronal network dynamics but an ultra-sensitive detection method for brain-on-chip applications and neuro-analysis. Finally, discussion and outlook is made on the strategies through biolasers and to pioneer novel on-chip devices for future clinical diagnosis, prognosis, and fundamental research in biomedicine.
(Invited) Biomimetic Electronic Skins for Wearable Sensors
Authors: Ko Hyunhyub
Published: February 2020

Flexible physical sensors with high sensitivities have gained great attentions in the fields of wearable sensors, robotic skins, and biomedical diagnostics. Here, we introduce several biomimetic approaches to develop high-performance flexible electronic skins and their applications in wearable sensors. First, by mimicking the structures and functions of fingertip skin, we introduce highly-sensitive, multifunctional, and stretchable electronic skins. Inspired by the interlocked microstructures found in epidermal-dermal ridges in human skin, piezoresistive interlocked microdomes are employed for the demonstration of stress-direction-sensitive, stretchable electronic skins. We show that interlocked microdome arrays possess highly direction-sensitive detection capability of various mechanical stimuli including normal, shear, stretching, bending, and twisting forces. We also demonstrate that ferroelectric skins with fingerprint-like patterns and interlocked microstructures can detect and discriminate multiple spatio-temporal tactile stimuli including static and dynamic pressure, vibration, and temperature with high sensitivities. For wearable device applications, we show that stretchable electronic skins attached on the human skin can be used as wearable healthcare monitoring devices, which are able to distinguish various mechanical stimuli applied in different directions, selectively monitor different intensities and directions of air flows and vibrations, and sensitively monitor human breathing flows and voice vibrations. In addition, dynamic touch sensing ability is employed for precise detection of acoustic sounds, and discrimination of various surface textures. For skin attachable devices, we also introduce smart adhesive pads based on octopus-inspired theremoresponsive adhesive pads. Finally, we demonstrate conductive and ultrathin nanomembranes for skin-attachable microphones and speakers.
(Invited) Merging Humans and Machines with Hydrogel Bioelectronics
Authors: Zhao Xuanhe
Published: February 2020

While human tissues are mostly soft, wet and bioactive; machines are commonly hard, dry and biologically inert. Bridging human-machine interfaces is of imminent importance in addressing grand societal challenges in healthcare, security, sustainability and joy of living. However, interfacing human and machines is extremely challenging due to their fundamentally contradictory properties. At MIT SAMs Lab, we propose the Hydrogel Technology to bridge human-machine interfaces. On one side, hydrogels with similar mechanical and physiological properties as tissues can naturally integrate with human body, playing functions such as scaffolds, catheters, stents and implants. On the other side, the hydrogels embedded with electronic and mechanical components can control and respond to external machines. In this talk, I will first discuss the mechanics to design extreme properties for hydrogels, including tough, resilient, adhesive, strong and antifatigue, which are necessary for reliable robust human-machine interfaces. Then I will discuss a set of novel soft hydrogel devices that interface with the human body, including i). long-term high-efficacy hydrogel neural probe, ii). ingestible and GI-resident hydrogel machine, and iii). untethered fast and forceful hydrogel robots controlled by magnetic fields. I will conclude the talk by proposing a systematic approach to design next-generation human-machine interfaces based on hydrogel technology.
(Invited) Gold Electronic Skins
Authors: Cheng Wenlong
Published: February 2020

Next generation of electronic devices will be not only flexible but also stretchable, enabling applications impossible to achieve with existing rigid circuit board technologies. This needs new materials and new design principles. Among various materials of choices, gold has advantages of biocompatibity, chemical inertness and band-gap-matching with a lot of semiconductors materials. In this talk, I will discuss the Monash e-skin-based wearable technology platform using ultrathin gold nanowires. We have demonstrated their applications in skin-like pressure sensors, strain gauge sensors and transparent energy storage devices. Our sensors can communicate via smartphone, indicating the potential of remote health management anytime anywhere.In comparison to other nanomaterials, gold nanomaterials offer the advantages such as good biocompatibility, chemical inertness and facile synthesis at large scale.
Multi-Responsive Hydrogel Based Flexible Sensors for Plants/Animals Metabolic Stress Analytics
Authors: Mugo Samuel , Alberkant Jonathan , Yu Nancy , Lu Weihao
Published: February 2020

Versatile and non-invasive multiresponsive flexible sensor platforms developed in our research group will be demonstrated in this talk. The sensor platforms are fabricated by contact printing on a composite carbon nanotubes/polyaniline conductive flexible films, embedded with multi-responsive (redox, ionic strength, pH) molecularly imprinted responsive polymer hydrogels, highly selective biomimetric molecular receptors.

In this presentation, data highlighting the sensor platforms when applied for dosimetric and real-time monitoring of metabolic stress biomarkers in plants and animals will be discussed.

With standout customization and versatility, the flexible wearable sensors are interfaced to Bluetooth, which transmits data wirelessly to a mobile device, demonstrating their utility for autonomous deployment in health/wellness diagnostics and precision agriculture.
Evaluation of on-Body Performance of a Sweat-Based Lactate Sensor from Low Volumes of Passive Eccrine Sweat
Authors: Bhide Ashlesha , Prasad Shalini , Muthukumar Sriram
Published: February 2020

Lactate is a critical biomarker that can be used to monitor physical performance in sports medicine and restricted oxygen supply to tissues during anaerobic respiration for diagnosing clinical conditions such as hypoxia, cystic fibrosis, and ischemia. Recent advances have been made towards understanding accessible human biofluids to non-invasively monitor biomarkers that reflect the state of the body. Passive eccrine sweat is a potential candidate containing valuable information due to its ease of access, collection, and analysis. Literature studies have shown clinical correlations between sweat lactate and blood lactate levels which confirm that there is value in investigating sweat lactate for investigating clinical conditions. Existing wearables devices monitor only digital biomarkers to track heart rate and physical activity, however, there is no information obtained on human health status which can be understood by probing biochemical markers. The motivation of this study is to demonstrate on-body, low-volume detection of lactate in passive eccrine sweat. An electrochemical biosensor fabricated on a flexible, nanoporous substrate that can wick sweat is placed on the subject’s lower back and is utilized to detect and quantify sweat lactate levels. Label- free AC- based electrochemical impedance spectroscopy (EIS) is the signal transduction technique used to report the impedance in response to the lactate present in the passive body sweat. Prior to on-body testing, the functionality and the metrics of the lactate sensor in detecting sweat lactate within the physiological relevant ranges (5- 60mM) will be tested in controlled lab- environment to build a calibration response of curve of mapping impedance ranges to the lactate level for dynamic reporting of lactate concentrations when placed on-body. Sensor metrics obtained in human sweat from current bench top testing have yielded a 1mM as the lower limit of detection and a dynamic range of 1- 100mM. The on-body impedance response profiles produced corresponding to the lactate levels in continuous, real- time detection mode on integration with portable electronics will allow for translation into wearable biosensing applications.
Solar Powered Monitoring System Development for Smart Farming and Internet of Thing Applications
Authors: Chung Wen-Yaw , Luo Reng-Hong , Chen Chien-Lin , Heythem Salhi , Chang Chieh-Feng , Po Chi-Chao
Published: February 2020

This paper is mainly aimed to develop a solar powered hand-held monitoring system for real-time crop-growth multiple environment parameter sensing and ZigBee-based wireless data transmission for Internet of Thing (IoT) applications.

Regarding the problems of less man-power and difficult farm management in aging farmer population in many countries, in order to assist famers to monitor the status of plant growth and green-house condition in real time, this research focuses on the use of solar panels (5V/240mA 90mm2) and the buck converter IC to charge 18650 Lithium ion batteries used for hand-held monitoring system. The battery output will be coupled to a Low-Dropout (LDO) regulator, then generate a stable voltage to the CC2530 node. Solar panels will be integrated with the rechargeable batteries to yield more efficient power management. This paper proposes a LDO design for 18650 Lithium ion batteries. It will convert a supply voltage from 3.7V into 3.3V for driving the CC2530 and the sensors.

The proposed solar powered system successfully built a Wireless Sensor Network (WSN) for quality agriculture application by using the ZigBee technology standard and TI’s CC2530 chip. Commercially available sensors were utilized specifically for temperature, humidity, soil moisture, light, chlorophyll, and CO2 monitoring. With the consideration and advantages of low power, low cost and multi-node capabilities, we chose ZigBee-based wireless network to transmit data into the cloud system for further data processing and analysis. When the sensors and Zigbee transmission system are set up, the data obtained through the human machine interface on the host will be sent to the cloud database established by MySQL in XAMPP. The management and data storage of the cloud database are both processed under the phpMyAdmin system. In addition, we use another program in XAMPP - Apache HTTP Server to set up the php website. Finally, this database of the sensing information will be used for assessment and evaluation of the environmental condition, data log recording, risk management and decision making. These resources can feed back to farmer’s cell phones through a decision support system. The experimental design and field test were verified in Tai-Yuan Organic farm located in Tao-Yuan County, Taiwan. The system will have a potential to be deployed into an open-field or green-house based farm to improve the optimized crop cultivation and increase the harvest yield.

Figure 1
(Invited) Hybridized Electronics for Wearable Healthcare: From the Skin to below the Skin
Authors: Xu Sheng
Published: February 2020

Wearable electronic devices that can acquire vital signs from the human body represent an important trend for healthcare. Combined strategies of materials design and advanced microfabrication allow the integration of a variety of components and devices on a stretchable platform, resulting in systems with minimal constraints on the human body. We have demonstrated a skin-mounted multichannel health monitor that can sense local field potentials, temperature, strain, acceleration, and body orientation. Integrating ultrasonic transducers on this stretchable platform adds a third dimension to the detection range by launching ultrasound waves that reach well underneath the skin. The ultrasound waves allow capturing a wide range of dynamic events in deep tissues such as blood pressure in central arteries and veins. This technology holds profound implications for continuous and noninvasive sensing, diagnosis, and treatment of chronic diseases.
Alkaline Water Electrolysis at 20 a cm-2 with a Microfibrous, Flow-through Electrolyzer
Authors: Yang Feichen , Kim Myung Jun , Wiley Benjamin J.
Published: February 2020

Improving both the efficiency and productivity of water electrolysis is necessary for making the electrochemical generation of hydrogen economically competitive. Flow-through electrodes are widely used to improve the efficiency and productivity of electrochemical processes, but studies of their use in alkaline water electrolysis are relatively rare. This work aimed to (1) test the hypothesis that the use of a flow-through electrode could enhance the rate of bubble removal from the electrode surface, thereby improving productivity, and (2) determine what length scale of electrode would maximize the surface area available for electrolysis without hindering bubble removal. To determine how the efficiency and productivity of the flow-through electrode depends on the electrode length scale, the performance of the oxygen evolution reaction was compared with flow-through electrodes consisting of a Ni foam, Ni microfibers (Ni MFs, d = 1.2 mm), and Ni-coated Cu nanowires (NiCu NWs, d = 350 nm). Although the turnover frequency (TOF) for the Ni foam was 2.4 times higher than the Ni MF electrode and 42 times higher than the NiCu NW electrode, its surface area was more than 90 times lower than the other electrodes, resulting in the lowest overall current density. Although the NiCu NW electrode had a higher surface area than the Ni MF electrode, it had a lower overall current density because of its low TOF. We attribute the high performance of the Ni MF electrode to the fact that the mean pore size of the Ni MF electrode (5-10 mm) is on the order of the mean bubble size (20 mm) that was measured by examining the bubbles generated from a mesh electrode. The performance of the Ni MF electrode was further improved by coating it with a Ni-Fe layered double hydroxide (LDH) catalyst, resulting in an OER overpotential of 247 mV at 0.1 A cm-2 and a Tafel slope of 26 mV dec-1. These values are among the lowest reported for Ni-Fe LDH catalysts. A Ni MF anode was paired with a Pt-coated Ni MF cathode to measure the overall productivity for water splitting. The maximum current density for water splitting was 20 A cm-2 at 3.9 V in 30% KOH, which is 20 times greater than the highest current densities previously reported for alkaline water electrolysis. This current density and voltage could be sustained for at least 8 hours with no signs of degradation. This high current density was attributed to the ability of the flowing fluid to promote bubble removal and keep the hot electrode surface from boiling water. This work demonstrates that flow-through microfibrous electrodes can improve the efficiency and productivity of alkaline water electrolysis.

Figure 1
Electrodeposition of Co-W Coatings from Acidic-Citrate Solutions for Hydrogen Evolution
Authors: Kwiecińska Anna Maria , Kolczyk Karolina , Skibinska Katarzyna , Kutyla Dawid , Zabinski Piotr , Kowalik Remigiusz
Published: February 2020

The electrochemical deposition of cobalt binary alloys with transition metals has received recently much attention due to some characteristic properties and possible practical applications of the coatings. These alloys, besides useful mechanical properties, exhibit valuable features like high corrosion resistance and low overpotential for hydrogen evolution reaction. Among many possible used alloy additives, tungsten seems to be the most promising to improve the catalytic and anti-corrosive properties of cobalt. Furthermore, the electrochemical method of coatings deposition features many advantages compare to other methods, even though the tungsten electrodeposition is very difficult due to its complex chemistry. It is still remains a challenge for many scientists to choose the optimal electrolyte composition and optimal parameters of the electrolysis process to obtain the cobalt alloy with the highest tungsten content.

The present work aims to deposit of thin layered active cobalt alloy cathodes for hydrogen evolution. Electrodeposition mechanism and kinetics of cobalt and tungsten from acidic – citrate solutions was studied by electrochemical methods. In the present investigation, the composition of the electrolyte, potential and current density were changed systematically in ranges within which they significantly affect on the composition and structure of the resulting Co – W alloy. The proper adjustment of the process of electrolysis has a crucial role on the composition and structure of the deposited films, which decide about their electrocatalytic properties. The presence of cobalt and tungsten were confirmed by X-ray spectrofluorometry and electron probe microanalysis. In order to determine the phase composition and the morphology, the obtained coatings were analysed with the use of x-ray diffraction and scanning electron microscopy. Next the electrochemical properties of the coatings were examined in sulfuric acid and sodium hydroxide solutions.

This work was supported by the Polish National Centre of Science under grant UMO-2016/21/B/ST8/00431. The authors would like to acknowledge the COST MP1407 Action for networking.
The Mechanism of Proton Diffusion in ABO3 Perovskite Structure
Authors: Aluru Narayana R. , Jing Yuhang
Published: February 2020

Perovskite oxides (ABO3) are well-known proton conductors. However, the role of A-site ion on proton diffusion in a perovskite oxide is not clear. By performing detailed density functional theory (DFT) calculations, we investigate the effect of A ion vacancy on proton transfer in Y-doped BaZrO3, which is one of the widely studied perovskite oxide. We found that the presence of A ions reduces the barrier for proton diffusion in a perovskite oxide, demonstrating the significance of perovskite structures as proton conductors. We show that the proton movement in a perovskite oxide is governed by hydroxide ion rotation and proton transfer from one oxygen to another. Both these motions are strongly coupled to lattice deformations. We identify the key physical mechanisms and the energy barriers associated with both hydroxide rotation and proton transfer by performing NEB calculation. Finally, we also calculate the bond strength and show that the presence of an A ion can reduce the bond strength between O and B ions, thereby reducing the energy barrier for local lattice deformations.
(Invited) In Situ x-Ray Absorption Spectroscopy Studies of Catalysts for Water Spitting
Authors: Feng Zhenxing
Published: February 2020

Electrocatalysis plays a key role in producing/converting molecular energy carriers and metal to either store electricity from solar or wind energy in chemical forms or produces electrical energy through fuel cells and metal-air batteries. In the search of highly efficient electrocatalysts, it is important to understand how catalysts work, then subsequently a ration design rule can be provided. We use several in-situ synchrotron X-ray techniques, particularly X-ray absorption spectroscopy (XAS), to probe the element-specific changes from heavy metal (e.g., Mn, Co, Fe, etc) to light element (e.g., O, N) during various electrochemical reactions including oxygen evolution/reduction and hydrogen evolution/oxidation reactions. We not only directly observe how catalysts adjust their local structures and valence state to promote reactions, but also identify different reaction centers that weren’t considered before and couldn’t be found from ex situexperiments. In my talk I will show couple of cases to highlight the importance of our in situstudies as well as new thoughts for catalystdesigns.
Compositional and Microstructural Engineering of Transition Metal Phosphides for Improved Electrocatalytic Performance
Authors: Liu Lifeng , Xu Junyuan
Published: February 2020

Water splitting has been proposed to be a promising approach to renewable energy storage through converting the off-peak solar or wind energy to hydrogen fuels. Presently, one of major challenges facing widespread deployment of water splitting devices is their high cost, which primarily results from the use of precious and scarce noble metal catalysts.

In this talk, I will present our recent efforts towards compositional and microstructural engineering of transition metal phosphide (TMP) electrocatalysts, with an aim to improve their electrocatalytic performance for the oxygen evolution reaction (OER). I will showcase two examples: 1) Trends in the OER activity of TMP nanoparticles [1]. We have investigated the alkaline OER electrolysis of a series of TMP catalysts and observed a notable trend in OER activity which follows the order of FeP < NiP < CoP < FeNiP < FeCoP < CoNiP < FeCoNiP. Our results show that the introduction of a secondary metal(s) to a mono-metallic TMP can remarkably boost the OER performance. This promotional effect can be ascribed to the enhanced oxidizing power of bi- and tri-metallic TMPs. 2) Hollow CoP octahedron (OCH) nanostructures with well-defined exposed crystal facets [2]. The hollow CoP OCH NPs were prepared by solution phase synthesis of CoO OCH precursors, followed by a post-phosphorization treatment and subsequent chemical etching process. They show excellent intrinsic electrocatalytic performance for the OER, substantially outperforming CoP nanospheres without any preferentially exposed facets and many other non-precious OER catalysts reported in the literature.

Acknowledgements

Financial support from the EU Horizon2020 project “CritCat” (grant no. 686053) and the Portuguese Foundation of Science and Technology (IF/01595/2014) is acknowledged.

REFERENCES

J.Y. Xu, J. J. Li, D.H. Xiong, B.S. Zhang, Y.F. Liu, K.H. Wu, I. Amorim, W. Li, L.F. Liu, Chem. Sci. 9 (2018) 3470

J.Y. Xu, Y.F. Liu, J.J. Li, I. Amorim, B.S. Zhang, D.H. Xiong, N. Zhang, S.M. Thalluri, J.P. Sousa, L.F. Liu, J. Mater. Chem. A 6 (2018) 20646.
Unique-Structure MoS2 Grow on Nickel Foam As Highly Efficient Self-Supported Electrode for Oxygen Evolution Reaction
Authors: He Zizhou , Guo Hui , Ardoin Sydney , LaCoste Jed , Fei Ling
Published: February 2020

Growing demand for sustainable, clean, efficient energy conversion system has derived tremendous interest to develop cost-effective and highly efficient electrocatalysts for oxygen evolution reaction (OER). Sulfides have recently attracted great attention due to their highly efficient electrocatalytic activity. MoS2 has been verified as an efficient catalyst toward OER because of its durability, cost-efficiency and high activity. However, binder and extra conductive materials are required to attach electrocatalyst on a conductive substrate which will result in restricted active surface areas, undesirable interfaces and lots of dead volumes. Binder-free self-supported material can eliminate these problems. Herein, we synthesize self-supported binder-free MoS2 on 3D porous nickel foam (NF) with excellent activity and stability via a facile hydrothermal method. The MoS2@NF electrode is tested in 0.1mol KOH by linear sweep voltammetry (LSV), electrochemical surface area (ECSA) and electrochemical impedance spectroscopy (EIS). Compared with different substrates (Cu foam, NF, Cu paper and carbon paper), MoS2@NF electrode where NF as substrate shows the lowest overpotential at 10mA cm-2 of 359mV for OER. Furthermore, the overpotential at 10mA cm-2 after 10hr is 419mV, which demonstrates high stability and activity. Such high electrochemical performance may attribute to the following reasons: 1) the large ECSA and good conductivity, that improves utilization of electroactive sites and electron transfer; 2) the unique 3D porous structure, that facilitates electrolyte penetration and reactant/product diffusion; and 3) the sulfur vacancy in MoS2, that accelerates the O-H bond breaking.
Ni-Fe-Based Nanostructures for Oxygen Evolution Reaction in Alkaline Media
Authors: Manso Ryan , Prashant Acharya , Greenlee Lauren F. , Chen Jingyi
Published: February 2020

Controlling morphology, composition, and crystalline phase of Ni-Fe-base nanostructures is of great interests in the development of nanocatalysts for improving the sluggish kinetics of oxygen evolution reaction (OER) in alkaline media. This work develops a scalable, solution-based synthesis approach based on thermal decomposition of organometallic complexes that enables manipulation of both the morphology and crystalline phase of the Ni-Fe nanocatalysts. Different design of morphologies including core-shell and alloy nanostructures are synthesized via either sequential or simultaneous injection. Using fine control of reaction kinetics, the resulting Ni-Fe-based nanostructures exhibit high uniformity with ultrafine size. These uniform nanostructures allow us to use transmission electron microscopy (TEM) including high resolution TEM and electron energy loss spectroscopy (EELS) for in-depth structural and electronic characterization of single particles. The quantitative analysis of the elemental distribution on individual particles using EELS not only matches well with that of the bulk measurement using inductively coupled plasma mass spectrometry but also reveals additional information for the composition of nanoparticles with uneven elemental distribution. Together with the x-ray methods including x-ray power diffraction, x-ray photoelectron emission spectroscopy, x-ray absorption spectroscopy on the bulk sample, we elucidate the morphology, composition, and structure of individual particles for each of these nanostructures in detail. Semi-quantitative analysis of the electronic structures using EELS on single particles agrees with the results from the x-ray techniques. We then evaluate the OER performance for these well-defined, Ni-Fe-based nanostructures and compare with Ni and Fe alone nanoparticles. Through this study we establish a fundamental understanding of morphological, compositional, and structural influences on the electrocatalytic activity of Ni-Fe-based nanocatalysts for OER and identify the best performed nanocatalysts to guide the design of future OER nanocatalysts for anion exchange membrane based electrocatalysis.
TiO2-MoOx-Supported Iridium As Electrocatalysts for the Oxygen Evolution Reaction in PEM Based Electrolysis
Authors: Kim Eom-Ji , Shin Jaewook , Cho EunAe
Published: February 2020

Polymer Exchange Membrane water electrolysis (PEMWE) is promising energy converting device, which is one of the main component for hydrogen society. However, there are still some issues about prices and durability. Especially, in the anode electrode which the oxygen evolution reaction (OER) occurs, a large amounts of precious metal catalyst is required to show quite good efficiency. Besides, durability issues occurs in anode side due to their high voltage and acidic conditions. To solve the issues, supporters have been proposed. According to the recent studies, the catalyst stability in the OER could be improved by using metal-support interaction. Here, we report TiO2-MoOx supporter for the OER in PEMWE. In half-cell test, TiO2-MoOx-supported Iridium catalyst shows high activity and stability compared with commercial iridium on carbon and Iridium black. Moreover, TiO2-MoOx-supported Iridium catalyst shows better stability than TiO2 supported Iridium. It seems that the main reason to improve stability is originated from interaction between Iridium and TiO2-MoOx. These results demonstrated that TiO2-MoOx supporter can be utilized for a new active and durable the OER supported catalyst in PEMWE.
Electroless Deposited IrOx Nanoparticles for Ni Foam Functionalization with Low Iridium Loading
Authors: Milazzo Rachela Gabriella , Privitera Stefania M S , Scalese Silvia , Monforte Francesca , Condorelli Guglielmo Guido , Lombardo Salvatore
Published: February 2020

Hydrogen is potentially a reliable, affordable and sustainable energy carrier. Unfortunately hydrogen gas must be usually be generated from other compounds: 96% of Hydrogen is still extracted from fossil fuels, such as natural gas, oil and coal. The generation by electrolysis using the solar energy is a promising carbon free approach but it needs to be improved in terms of efficiency and durability to become economically appealing. A crucial factor is represented by the electrode and catalyst materials. The catalysts with highest activity and stability are noble or rare materials. In particular, IrO2 represents the best compromise for an active and stable oxygen evolution reaction catalyst. In order to minimize the amount of rare material, an affordable technique consists in depositing the catalyst on the surface of a less noble metal, such as nickel or steel. The deposition of IrO2 usually requires high temperature (200-1000°C), high purity precursors and complex experimental set up. In this paper we propose the use of electroless deposition through spontaneous galvanic displacement as a promising and simple deposition technique to produce interconnected IrO2 nanoparticles on nickel foam electrodes (figure 1). The deposition process of Ir on Ni has been studied as a function of time, pH and temperature. The formation of the iridium oxide has been achieved by thermal annealing in air. The experimental conditions have been optimized in order to improve the catalytic activity during water splitting measurements in 1M KOH, using a saturated calomel electrode (SCE) as reference and a Pt wire as counter. Scanning Electron Microscopy (SEM) analyses, coupled with X-ray Energy Dispersive Spectroscopy (EDX) and X-Rays Photoelectron Spectroscopy (XPS) show that, under proper deposition conditions, we can overcome the limits of other deposition techniques, achieving a uniform IrO2 coverage throughout the 3D structure of the Ni foam. Such a condition is crucial for the long term stability of the electrodes under constant current stress. The amount of Ir on the Ni foam has been experimentally evaluated, obtaining optimal results with 8 mg cm−2 of noble metal in a 0.16 cm thick electrode. Such a value is more than two orders of magnitude lower than typical values employed in the PEM electrolyzers, therefore making the present approach very promising.

Figure 1
Iridium-Based Catalysts for Acidic Water Splitting: Oxygen Evolution and Dissolution Mechanisms
Authors: Cherevko Serhiy , Mayrhofer Karl , Kasian Olga , Geiger Simon
Published: February 2020

Over the last half century, iridium is the state-of-the-art anode catalyst in acidic water splitting. Despite the fact that iridium is one of the rarest elements on the Earth, its relatively good activity and stability make it indispensable. In this situation, when viable alternative catalysts are absent and there is no time for identifying and testing new candidates, smart utilization of iridium in catalyst layers (CLs) becomes of a very high importance. Current approaches on the way of optimizing Ir usage by decreasing iridium loading include: (a) formation of highly porous IrOx CLs; (b) using Ir based catalysts like perovskites and mixed oxides; (c) using conducting supports. While enhancement of gravimetric Ir activity may indeed be achieved, each of these strategies may lead to deterioration in stability.

In this presentation I will show that improving Ir utilization going from rutile to more active catalysts like hydrous Ir oxides leads to a change in the oxygen evolution reaction (OER) mechanism and subsequent increase in Ir dissolution. Based on our recent mechanistic studies, it will be shown that lattice oxygen participation in OER is the bottleneck in materials’ stability.1,2 The latter conclusion is also valid for Ir-based single and double perovskites.3 Finally, utilization of conductive supports will be presented as challenging, as most (all?) of such oxides are intrinsically unstable during acidic OER.4 In this situation an alternative solution must be suggested, as will be discussed during the presentation.

Literature:

1 Cherevko, S. et al.
J. Electroanal.
Chem.
774, 102-110, (2016).

2 Kasian, O. et al.
Angew Chem Int Ed Engl
57, 2488-2491, (2018).

3 Geiger, S. et al.
Nature Catalysis
1, 508-515, (2018).

4 Geiger, S. et al.
Scientific Reports
7, 4595, (2017).
Direct Visualization of Ultra-Fast and Micro-Scale Bubble Evolutions and Electrochemical Reactions in Proton Exchange Membrane Electrolyzer Cells
Authors: Li Yifan , Yu Shule , Yang Gaoqiang , Talley Derrick A , Zhang Feng-Yuan
Published: February 2020

The electrochemical reactions and two-phase flow that occur in energy devices could be a very important part in promoting energy efficiency of both engineering and sciences. The electrochemical reactions only occur at a micro scale at the center part of the electrochemical devices like fuel cells and electrolyzers. The objective of this research is to visualize the bubble generation and growth process inside a proton exchange membrane electrolyzer cell (PEMEC) by taking advantage of the thin/well tunable liquid gas diffusion layer (LGDL) and high-speed visualization system. The effects of temperature, current density, and flow rate on bubble dynamics in pore scale and multiphase flow in channel scale, including bubble nucleation, growth, and detachment, are investigated. The reaction sites and rapid bubble evolution phenomena are captured under various operating conditions. The number of reaction sites and bubble growth rates increases with the operating current density and temperature, while the flow rate in the channel has limited effects. The gas bubbles are observed to emerge at the edge of the LGDL pores and gradually detach from the reaction sites. This work will provide a pathway to further investigate the electrochemical reaction in energy devices.
A Highly Active and Stable Electrocatalyst Based on Nicos Nano-Flower Structure for Hydrogen Evolution Reaction
Authors: Ali Yousuf , Nguyen Van-Toan , Nguyen Ngoc-Anh , Choi Ho-Suk
Published: February 2020

Developments of high and efficient electrocatalyst are significant attentions for the hydrogen evolution reaction. Platinum metal group and its alloys represent the most efficient catalytic activity for hydrogen evolution reaction (HER). However, the high cost and low abundant of Pt metal impede their commercial scale-up application. To solve these problems, the transition-metal based catalysts are developing to alter Pt-based catalysts. In this work, we used carbon dot (C-dot) as a structure-directing agent to first synthesize NiCoOH nano-flower, and then, sulfur atomss were solvothermally dopped into the NiCoOH nano-flower to generate the NiCoS nano-flower. The NiCoS nano-flower structure shows an onset potential of 90 mV, and an overpotential of 232 mV at a current density of 10 mA cm−2 and a Tafel slope of 80.17 mV dec−1. Furthermore, the Rct value of the NiCoS is 63.3 Ω. Especially, as-prepared catalyst shows an excellent long-term durability, which was confirmed by chronopotentionmetric response for 20 hours to maintain current densities at 10 mA cm−2. Therefore, this catalyst can be considered as a promising candidate for hydrogen production.
Surface Ligand Effects on Ni-Fe-Based Nanocatalysts for Oxygen Evolution Reaction
Authors: Manso Ryan , Acharya Prashant , Greenlee Lauren F. , Chen Jingyi
Published: February 2020

One of the most critical limitations of water electrolysis in alkaline media is overcoming the slow electron kinetics required to evolve oxygen. Typically, the oxygen evolution reaction (OER) is carried out on the surface of a catalyst in alkaline media; therefore, we expect the surface chemistry to play a crucial role in determining the overall efficiency of this process. Recently, we have demonstrated a scalable synthesis of Ni-Fe-based nanoparticles in an oil-based solution. While the atomic structure plays a crucial role in their catalytic activity, another important factor that must be considered is the surface ligand functionalization needed in order to transfer the nanostructure into aqueous, alkaline media. In this study, these previously-developed nanocatalysts will be utilized to vary the surface ligands for evaluation of their OER performance. The effects on different surface ligands on OER activity will be discussed to establish an essential understanding of how it may influence the electron kinetics at the surface.
Bifunctional Transition Metal Oxide-Based Oxygen Electrode Catalysts for Unitized Reversible Fuel Cells
Authors: Choi Sung Ryul , Lee Sungwon , Park Jun-Young
Published: February 2020

While the global warming and environmental pollutions have been emerged as international issues, hydrogen, which is renewable and sustainable energy source has received extensive attentions. Especially, unitized reversible fuel cells (URFCs) are considered as a prospective electrochemical energy conversion device due to their high energy efficiency and non-polluting system [1]. However, sluggish electrochemical kinetics and overpotential loss for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in both electrodes are still the biggest technical obstacles for entering into the real markets [2]. Until now, platinum-based noble metals such as platinum, iridium, and their alloys have been used for OER and ORR catalysts because of their high electrocatalytic activity [3]. However, the main weaknesses of these materials are low durability, low bifunctionality, and high price [4, 5]. In order to overcome these barriers, non-precious transition metal oxide-based material have regarded as promising alternative for bifunctional electrocatalysts due to their low price and high durability [6]. In this study, to increase intrinsic property and electrical conductivity of catalysts for OER and ORR, doping of other transition metals with various high surface area carbonaceous materials as a supporting material is adopted. The synthesized catalysts are analyzed by various physicochemical and electrochemical tools [7. 8].

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Keywords: Oxygen evolution reaction; Oxygen reduction reaction; Bifunctional electrocatalysts; Unitized reversible fuel cell; Transition metal oxide.