bluuebunny/crossref_metadata_2025 huggingface dataset:
Sputtered Pt3Y Thin Films As Cathode Catalysts with High Activity in PEMFC Measurements
Authors: Lindahl Niklas , Eriksson Björn , Grönbeck Henrik , Lindström Rakel Wreland , Lindbergh Göran , Lagergren Carina , Wickman Björn
Published: February 2020

Proton exchange membrane fuel cells (PEMFCs) have the potential to become a vital part of sustainable energy systems, provided that cathode catalysts with higher activity and stability are developed. A very promising group of materials for the oxygen reduction reaction (ORR) is the group of alloys with platinum and rare earth elements.[1, 2].

We have recently showed that sputtered thin films of Pt3Y have specific activities for ORR up to seven times higher than polycrystalline Pt in rotating disk measurements, which is similar to that of bulk alloys.[3] In addition, sputtered thin films of Pt3Y with thicknesses about 3 nm show a mass activity more than an order of magnitude higher than state-of-the-art Pt nanoparticles.

However, in order to become realistic alternative catalysts these materials need to prove an increased activity also under real fuel cell conditions. By sputtering thin films of Pt3Y on gas diffusion layers (GDLs) we are able to construct full membrane electrode assemblies (MEAs) and evaluate these in single cell measurements.[4] The fuel cell measurements show that Pt3Y has a specific activity up to 2.5 times higher than pure Pt. Detailed characterization reveals important materials properties of the thin films and indicates that the catalyst structure of the films on GDL is not optimal. This suggests that even higher activities should be possible in the fuel cell if the electrode and catalyst structure is improved.

References

Escudero-Escribano, M., et al., Tuning the activity of Pt alloy electrocatalysts by means of the lanthanide contraction. Science, 2016. 352(6281): p. 73-76.

Greeley, J., et al., Alloys of platinum and early transition metals as oxygen reduction electrocatalysts. Nature Chemistry, 2009. 1(7): p. 552-556.

Lindahl, N., et al., High Specific and Mass Activity for the Oxygen Reduction Reaction for Thin Film Catalysts of Sputtered Pt3Y. Advanced Materials Interfaces, 2017. 4(13): p. 1700311.

Lindahl, N., et al., Fuel cell measurements with cathode catalysts of sputtered Pt3Y thin films. ChemSusChem, 2018. http://dx.doi.org/10.1002/cssc.201800023.

Caption. a) Electrochemical single cell characterization of Pt and Pt3Y sputtered catalysts in H2/O2, 80 °C, 1.5 bar absolute pressure, 100% RH, 20 mV s-1. Inset shows a schematic image of the atomic stucture of the Pt3Y. b) Bright-field TEM micrograph of as-sputtered Pt3Y thin film on GDL. The scale-bar is 50 nm.

Figure 1
(Invited) Addressing Interfacial Processes That Govern the Electrocatalyst Activity-Stability Balance
Authors: Snyder Joshua David
Published: February 2020

The boundaries of functional materials development are continually being pushed where length scales down to the order of nanometers have introduced multi-functionality into the next generation of materials. The complex morphologies and compositional gradients that define these nanomaterials open pathways to new modes of instability, requiring strategies to address these instabilities and prolong the operational lifetime of these materials in real-world devices.

For complex, three-dimensional morphologies, the activity/stability balance begins to shift where an additional mechanism of performance degradation driven by the tendency to reduce the overall surface free energy of the system, results in material instability. It is critical that a more detailed fundamental understanding of the mechanisms of morphological and compositional instability and degradation in these topologically complex electrocatalytic materials be developed in order to propose strategies to improve their operational lifetime.

Here we will present an analysis of the mechanisms of material degradation for electrocatalysts with complex, three-dimensional nanoscale morphology with emphasis on operational conditions relevant for the oxygen reduction reaction (ORR). With a more fundamental understanding of the sources of structural evolution and performance metric degradation, we highlight the influence of the metal/electrolyte interface in governing both stability and activity. We will also present results of several mitigation strategies for the inherent instability of the three-dimensional morphology and their impact on electrocatalyst activity and selectivity.
Self-Supported, Carbon-Free Bimetallic Two-Dimensional Nanoframes for High Activity and Stability Oxygen Reduction Electrocatalysts for Fuel Cells
Authors: Rhodes Christopher , Godinez-Salomon Fernando , Ying Yuanfang
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). Carbon-supported catalysts result in significant catalyst degradation at high potentials, and therefore carbon-free structures are of interest to provide improved durability. We have recently developed bimetallic two-dimensional (2D) nanoframes as an approach to translate 2D materials into self-supported, carbon-free electrocatalysts that have both significantly higher ORR catalytic activities and stabilities compared with conventional Pt/carbon electrocatalysts.1 Bimetallic Pt-M (M=Ni, Co) 2D nanoframes were synthesized by controlled thermal treatments of Pt-decorated M(OH)2 nanosheets. The nanoframes consist of a hierarchical 2D framework composed of a highly catalytically active Pt-M alloy phase with an interconnected solid and pore network that results in three-dimensional molecular accessibility. The Pt lattice distances within the Pt-M alloy were significantly smaller compared to those of Pt nanoparticles. Based on the unique local and extended structure, the ORR specific activity of Pt-Ni 2D nanoframes (5.8 mA cmPt
-2) was an order of magnitude higher than Pt/carbon. In addition, accelerated stability testing at elevated potentials up to 1.3 VRHE showed that metallic Pt-Ni 2D nanoframes exhibit significantly improved stability compared with Pt/carbon catalysts. The nanoarchitecture and local structure of metallic 2D nanoframes results in high combined specific activity and elevated potential stability. Different temperature/atmosphere treatments were determined to significantly alter the atomic-level structure and influence the electrochemical activity. Additional efforts are aimed at understanding the effect of altering the transition metal and treatment conditions on the structure and ORR activity and stability. The ability to create metallic 2D structures with 3D molecular accessibility opens up new opportunities for the design of carbon-free nanoarchitectures that function as high activity and stability oxygen reduction electrocatalysts for PEM fuel cells and other applications.

References

Godínez-Salomón, F.; Mendoza-Cruz, R; Arellano-Jimenez, M.J., Jose-Yacaman, M.; Rhodes, C.P; Metallic Two-dimensional Nanoframes: Design of Carbon-free Hierarchical Nickel-Platinum Alloy Electrocatalyst Nanoarchitecture with Enhanced Oxygen Reduction Activity and Stability, ACS Applied Materials & Interfaces, 2017, 9, 18660-18674. DOI: 10.1021/acsami.7b00043

Figure 1
Cathode Loading Impact on Voltage Cycling Induced PEMFC Degradation – a Voltage Loss Analysis
Authors: Harzer Gregor S. , Schwämmlein Jan Nicolas , Damjanović Ana Marija , Ghosh Sourov , Gasteiger Hubert A.
Published: February 2020

Proton exchange membrane fuel cell (PEMFC) based vehicles are on the verge of commercialization. However, significant hurdles for further market penetration of PEMFC vehicles are cost reductions by decreasing the amount of platinum catalysts while meeting long term durability targets. The durability of catalysts is usually estimated by accelerated stress tests (ASTs) using voltage cycling.[1] Generally, the electrochemically active surface area (ECSA) and mass activity of the cathode catalyst is analyzed over the course of 30000 voltage cycles, while effects of O2 mass transport related losses, especially for varying cathode catalyst loadings have not yet been systematically studied.

To better understand the influence of voltage cycling based ASTs on the development of mass transport resistances and on the extent to which they can be captured by currently available in situ diagnostics (ORR kinetics in H2/O2, cathode proton conduction resistance by impedance, oxygen transport resistance via limiting current measurements), we conducted a comprehensive voltage loss analysis on MEAs with high- and low-loaded cathodes (0.4 and 0.1 mgPt/cm2) over the course of ASTs conducted in H2/N2 (anode/cathode) at ambient pressure, 80 °C, and 100% RH, using different voltage cycling profiles: i) triangular wave (TW) and square wave (SW) cycles between 0.6 and 1.0 VRHE; ii) TW cycles between 0.6 and a lowered upper potential limit of 0.85 VRHE (TW-LUPL); and, iii) a combination of a triangular sweep between 0.6 and 1.0 VRHE with potential hold periods at the upper and lower potential (TW-H).

For all ASTs, the O2 transport resistance scaled inversely to the cathode electrode roughness factor (rf). Since the ECSA decreases in the course of potential cycling and two different loadings were used, a wide range of rf values with their corresponding pressure-independent O2 transport resistance was analyzed, proving its dependence on the available Pt surface area (Figure 1) as shown also by other researchers.[2] The pressure dependent transport resistance remained essentially constant. Furthermore, ex situ thickness measurements of catalyst layers showed no cathode thinning, indicating the absence of significant carbon corrosion. While 30000 TW or SW cycles dramatically decreased the H2/air performance for low- and high-loaded MEAs, only a negligible degradation in performance was observed when a lower upper potential limit of 0.85 VRHE was applied, providing a guideline to limit MEA degradation under automotive conditions.

Figure 1: Pressure independent O2 transport resistance vs the electrode’s roughness factor, rf, for high-loaded (0.4 mgPt/cm2, blue) and low-loaded (0.1 mgPt/cm2, orange) catalyst layers over the course of different voltage cycling ASTs.

Figure 1
Activity and Stability of Carbide Derived Carbon Supports in PEMFC Application
Authors: Sepp Silver , Nerut Jaak , Vaarmets Kersti , Kanarbik Rait , Tallo Indrek , Lust Enn
Published: February 2020

Polymer electrolyte membrane fuel cells (PEMFCs) are regarded as a promising alternative energy conversion devices for both mobile and stationary applications. Main problems hindering the wide-scale commercialization of PEMFCs are high overpotential for oxygen electroreduction reaction (ORR) at the cathode decreasing the efficiency as well as the instability of porous carbon supports in fuel cell working conditions. Therefore, novel catalyst materials are being sought for PEMFC applications [1, 2]. Hierarchical microporous-mesoporous carbon supports were prepared from molybdenum carbide using the high temperature chlorination method. Prepared materials exhibited high specific surface area and large mesopore volume [3-4].

Thermogravimetric analysis, X-ray diffraction, low temperature nitrogen sorption and high resolution transmission electron microscopy methods were used to characterize the structure of the synthesized catalyst materials.

Prepared catalysts were used in the single cell measurements. Catalyst coated membrane method was used to prepare the MEAs using ultrasonic spaying technique. The polarization curves and chronopotentiometric measurements were conducted to evaluate the activity and stability of the catalyst materials synthesized. From cyclic voltammetry the electrochemically active surface area values were calculated and used to estimate the contact surface of platinum nanoparticles and Nafion electrolyte. The series resistance of electrolyte, polarization resistance and activation energy values have been calculated from electrochemical impedance spectroscopy data. It was established that prepared carbon materials with well-defined properties are excellent objects to study the impact of the catalyst support properties on the performance of a PEM fuel cell.

It was found that the novel synthesized catalyst materials are very stable and catalytically active towards ORR. Therefore, prepared materials are suitable for PEMFC applications.

Acknowledgements.

This work was supported by Estonian target research project IUT20-13, Personal Research Grant PUT1033, Estonian Centre of Excellence Project No. 2014-2020.4.01.15-0011.

References

S. Sepp, K. Vaarmets, J. Nerut, I. Tallo, E. Tee, H. Kurig, J. Aruväli, R. Kanarbik, E. Lust, Electrochim. Acta 2016, 203, 221−229.

S. Sepp, K. Vaarmets, J. Nerut, I. Tallo, E. Tee, H. Kurig, J. Aruväli, R. Kanarbik, E. Lust, J. Solid State Electrochem. 2016, 21(4), 1035–1043.

S. Sepp, E. Härk, P. Valk, K. Vaarmets, J. Nerut, R. Jäger, E. Lust, J. Solid State Electrochem. 2014, 18(5), 1223 – 1229.

E. Lust, K. Vaarmets, J. Nerut, I. Tallo, P. Valk, S. Sepp, E. Härk, Electrochim. Acta 2014, 140, 294-303.
Highly Active and Durable Ceramic Carbide and Nitride Cathode Materials for PEM Fuel Cells Synthesized Via Facile Methods
Authors: Lori Oran , Elbaz Lior
Published: February 2020

Considering the need for alternative and efficient energy sources, fuel cells appear to be a viable and cost-effective solution. One of the more acute setbacks in the commercial distribution and utilization of this technology is the lifetime of the fuel-cell which is mostly limited by the stability of the electrode.1 In this regard, carbon-based materials are not suitable as an electrode material since carbon undergoes severe corrosion in fuel-cell ambience.

In the quest to find more durable alternatives, Nano-structures of ceramic carbides and nitrides such as Mo2C, TiN and more were synthesized via facile solid-state synthesis paths and utilized as support material for the deposition of Pt catalyst in order to be studied as durable, corrosion-resistant ceramic-based systems for the oxygen reduction reaction (ORR). Catalyst integration techniques that further increase the stabilization and corrosion-resistance of the catalyst-support systems were employed as well. Concurrently, these techniques also enable the usage of low Pt loadings in order to satisfy the economical issues arising due to the use of precious metal catalysts (PMC).

The synthesized ceramic compounds were found to be devoid of free carbon despite their organic precursors, making them potentially compatible as fuel cell electrode material.

Furthermore, they were found to be superior at almost every fuel cell-related parameter than any other equivalent carbonaceous systems examined. Parameters like ORR performance showed circa 10% more positive half-wave value, and corrosion resistance tested using accelerated stress tests (ASTs) showed about 40% better initial ECSA preservation. Additionally, even the post-AST Pt/ceramic systems were found to show more positive half-wave potential (around 30 mV) over the pre-AST carbon-based equivalent.2

The corrosion mechanism of these ceramic-based systems is also being under investigation which suggest the formation of several oxide species that tend to dissolve in the aqueous medium over time.

O. Lori and L. Elbaz Catalysts, 2015, 5, 1445.

O. Lori, S. Gonen and L. Elbaz, Journal of The Electrochemical Society, 2017, 164, F825-F830.
Electropolymerization of Metallo-Corroles: Formation of Highly Active Three-Dimensional Catalysts for Oxygen Reduction
Authors: Friedman Ariel , Gross Zeev , Elbaz Lior
Published: February 2020

Within the class of precious group metal-free (PGM-free) catalysts for oxygen reduction reaction (ORR), significant progress has recently been reported for 1st row transition metal complexes of corroles, which generally shows better catalytic activity when compared to other molecular, macrocyclic transition metal complexes such as porphyrins and phthalocyanines. In order to further enhance their catalytic activity and durability we recently reported on electropolymerization of CoIII corroles. The catalytic activity of the polyCorrole and its monomer for oxygen reduction reaction (ORR) was studied using rotating ring disk electrode (RRDE). The polyCorrole exhibits significantly better catalytic activity than its monomer, reflected in lower overpotential as well as higher selectivity to the desired 4e-/4H+ pathway, both attributed to synergistic biomimetic-like effect of the interconnected catalytic centers. In the current work, we further investigated the polymerization process, trying to determine the parameters influencing the catalytic activity and stability of the polymer, such as morphology, polymerization techniques, chemical environment etc. In addition, the stability of the polyCorroles were measured in order to understand the dominating failure mechanisms which will allows further improvement of the catalyst for application in fuel cells.
A Hybrid Organic Linker Forms an Efficient Non-Precious-Metal-Based Metal–Organic Coordination Network Porous Material for Oxygen Electroreduction Reaction
Authors: Kongi Nadezda , Ping Kefeng , Bhadoria Rohit , Kook Mati , Vlassov Sergei , Tammeveski Kaido , Starkov Pavel
Published: February 2020

Proton exchange membrane fuel cells (PEMFCs) are one of a few technological solutions that address both alternative energy demands and sustainability (by virtually converting dihydrogen and O2 to water).1 With the prices of precious metals (e.g. Pt, Pd, Au) remaining high, the electrodes’ materials for this type of devices have to be cost-efficient in order to drive the technology into the marketplace. While the state–of–the–art solutions remain being platinum-based and carbon-supported, the alternatives are highly sought after. One of the potential solutions recognized by the community is to use earth-abundant metal (Ni, Co, Fe)-based systems.

The design of efficient functional materials often requires exploration of new modes of connectivity. In porous coordination materials, the nature of an organic linker plays a crucial role. Metal–organic frameworks have recently shown a well-received attention in addressing the need for new solutions in energy conversion and storage.2-4

While symmetric linkers are widely employed, we show that a non-symmetric, electron-rich merged scaffold allows for fabrication of crystalline and amorphous metal-organic coordination networks. We have further utilized them to fabricate a non-supported material that shows high electrochemical oxygen reduction performance in alkaline medium with the onset and half-wave potential higher than that of the state-of-the-art 20 wt% Pt/C catalyst.

References

M. K. Debe, Electrocatalyst approaches and challenges for automotive fuel cells, Nature, 486
, 43 (2012).

H. B. Wu and X. W. Lou, Metal-organic frameworks and their derived materials for electrochemical energy storage and conversion: Promises and challenges, Sci. Adv., 3
, eaap9252 (2017).

P.-Q. Liao, J-Q. Shen, and J.-P. Zhang, Metal–organic frameworks for electrocatalysis, Coord. Chem. Rev., (2018) in press, DOI:10.1016/j.ccr.2017.09.001.

M. Shao, Q. Chang, J.-P. Dodelet, and R. Chenitz, Recent advances in electrocatalysts for oxygen reduction reaction, Chem. Rev., 116, 3594 (2016).
Engineered Ptshell-Pdcore Bi-Metallic Catalyst for Active and Durable Alcohol Oxidation in Direct-Fuel Fuel Cells
Authors: Choi Insoo , Lim Dong-Hee , Shin Dong Yun , Cho Yong-Hun
Published: February 2020

Pt-Pd nanoparticles are structure-engineered by successive electroless deposition and galvanic displacement technique, to manifest a shell-core configuration. Based on the microscopic analysis, the nanoparticles present an uniform distribution. When applied as an electrocatalyst, they are confirmed to be highly active toward both methanol and ethanol oxidation reaction for a prolonged time. In addition, the catalyst is more resistive against CO-poisoning than conventional Pt catalyst. The stable activity of Pt-Pd catalyst is ascribed to the surface-tuned electronic property of Pt over-layer, which leads to a weak adsorption strength to CO and a high affinity to OH. The modified binding ability of surface Pt was reflected by CO-stripping experiment and by monitoring of electrochemical surface area over multiple times. The observed chemical stability of as-prepared catalyst is further proved and supplemented by a computational investigation via density functional theory calculation. The experimental and theoretical outcomes indicate that the catalyst is suitable and applicable for the direct methanol and ethanol oxidation in DAFC.

Figure 1
(Invited) U.S. DOE Early-Stage Alkaline Membrane Fuel Cell R&D
Authors: Thompson Simon T. , Ho Donna , Papageorgopoulos Dimitrios C
Published: February 2020

The U.S. Department of Energy (DOE) supports research, development, and demonstration of fuel cell technologies for transportation, stationary, and early market applications. Fuel cell research and development (R&D) efforts predominantly concentrate on R&D of fuel cell stack materials and components to achieve low-cost, high performance fuel cell systems, and include longer term technologies, such as alkaline membrane fuel cells (AMFCs). More favorable oxygen reduction kinetics and increased platinum group metal (PGM)-free catalyst stability at high pH conditions have invigorated interest in alkaline membrane fuel cells as an alternative to polymer electrolyte membrane fuel cells (PEMFCs), on which fuel cell electric vehicles currently available for retail sale are based. The catalyst accounts for >40% of the projected high-volume stack cost in PEMFC electric vehicles, owing largely to the inclusion of PGMs [1]. Achieving cost competitiveness with internal combustion engine vehicles will be expedited by eliminating PGM-based catalysts; AMFCs offer a promising route for successfully incorporating state of the art PGM-free catalysts into membrane electrode assemblies (MEAs).

Alkaline membrane R&D is targeted to increase the operating temperature and humidity ranges of fuel cells while improving conductivity and to increase membrane mechanical, chemical, and thermal stability with diminished fuel crossover. In 2016, an expert-led workshop on alkaline electrolyte membranes (AEMs) was convened by the DOE based on intense interest in the field and recent advances including performance of >1 W/cm2 in H2/O2 MEA testing [2]. There was consensus on the need for AEM-specific standardized protocols and testing and for further improvement in MEA performance. In order to accelerate materials development within the field, the DOE has set an AMFC-specific 2020 technical milestone of PGM-free MEA demonstration of >600 mW/cm2 performance in H2/air.

Stable, conductive polymer materials and durable hydrogen oxidation catalysts are key to realizing commercially relevant AEMFCs. Existing efforts in the DOE R&D portfolio include increasing performance and durability in perfluorinated and hydrocarbon-based ionomers, increasing cation group stability, diminishing catalyst deactivation due to ionomer-catalyst interaction, and PGM-free MEA performance of 350 mW/cm2.

Going forward, the profound lack of readily available, stable AEMs or ionomers for high pH MEAs must be addressed in order to expand entry into the field and foster more rapid progress in AEMFC development.

References:

[1] B. D. James, J. M. Huya-Kouadio, C. Houchins, D. A. DeSantis, "Mass Production Cost Estimation of Direct H2 PEM Fuel Cell Systems for Transportation Applications: 2017 Update," Strategic Analysis, Inc., 2017.

[2] U.S. Dept. of Energy. "2016 Alkaline Membrane Fuel Cell Workshop Report," Phoenix, AZ. April 1, 2016.
Synthesis and Characterization of Platinum-Praseodymium Oxide Nanocatalysts for Methanol Oxidation
Authors: Valk Peeter , Nerut Jaak , Kanarbik Rait , Aruväli Jaan , Paiste Päärn , Tallo Indrek , Lust Enn
Published: February 2020

Direct methanol fuel cells (DMFCs) are promising energy conversion devices, which can provide high efficiency and energy density, and as such, have been studied intensively. Due to the poisoning of Pt catalysts during methanol oxidation, various co-catalysts have been studied. Ruthenium has been studied extensively and good results have been obtained. More recently various oxide materials have been proposed and studied. Of these materials, rare earth metal oxides have been shown to be promising co-catalysts, although of the various oxides, CeO2 has perhaps received most attention.

In this study, praseodymium oxide containing catalyst materials have been synthesised and characterized. Praseodymium oxide containing nanocatalysts were obtained via deposition of praseodymium hydroxide onto a carbon support material and calcination of the resulting material. Thereafter, platinum nanoclusters were deposited onto the praseodymium oxide containing composite material by impregnation of the Pt precursor into the support material and further reduction with hydrogen.

The studied materials were electrochemically characterized using rotating disk electrode, cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy methods. Physical properties of the materials were characterized using X-ray diffraction, thermogravimetric analysis, scanning electron microscopy with EDX, inductively coupled plasma mass spectrometry and specific surface area measurements.

The studied materials exhibit high currents for methanol oxidation even at low Pt loadings. Compared to a commercial Pt-C(Vulcan) material, the overpotential was drastically reduced, and the peak potential for methanol oxidation is at E = 0.15 V vs mercury-mercurous sulfate electrode.

The good results of the study are a continuation of the investigation of nanocatalysts containing rare earth metal oxides for electrooxidation of alcohols.

Acknowlegements

This work was supported by the EU through the European Regional Development Fund Project TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011) and by the Estonian Research Council (institutional research grant IUT20-13, and PUT1581). P. Valk thanks Estonian Students Fund in USA for financial support.
Proton Conductor-bearing Material for Enhanced Catalytic Performance of Oxygen Electrode in Unitized Regenerative Fuel Cells
Authors: Jung Ho-Young , Roh Sung-Hee
Published: February 2020

There is little study on the preparation of non-conductive silica support for the fuel cell. It is expected that the sulfonation site in sulfonated silica (sSiO2) support can enhance the proton transfer property rather than the electron transfer. Therefore, we synthesize the sulfonated silica-supported Pt electrocatalyst for a bifunctional oxygen electrode in unitized regenerative fuel cell (URFC). A novel catalyst based on platinum on sulfonated SiO2 support aims for stabilizing cycle performance of URFC. It means that the usage of alternative sSiO2 is focused on suppressing the corrosion of support, whereas carbon support for the conventional oxygen electrode shows significant degradation in electrolyzer mode. In this study, the nano-morphology of our catalyst is confirmed by XRD and TEM. Electrochemical performances are analyzed by cyclic voltammetry (CV). Our new catalyst (46.1%) shows higher and stable performance during cyclic process due to the enhanced proton conduction property and low corrosion of the sulfonated silica support rather than the conventional Pt/C catalyst (45.3%). This means that the sulfonic acid functional group on the silica support can increase proton conductivity in the catalyst layer. Therefore, the ohmic resistance can decrease in the unit cell. Therefore, the sulfonated silica supported Pt electrocatalyst can be a promising candidate for bifunctional electrocatalyst in URFC.
Uio-66 As an Effective Support of Metal Oxides for Oxygen Evolution Catalysis
Authors: Andrade Angela Macedo , Liu Ziqi , Grewal Simranjit , Bai Seoung Jai , Lee Min Hwan
Published: February 2020

The most well-known electrocatalyst for oxygen evolution reaction (OER) have been noble metals or combination of them such as ruthenium, and/or iridium.1 Due to their cost and scarcity, however, there is a persistent search for alternative materials. Metal organic frameworks (MOFs) have recently attracted significant attention due to their versatility and stability in wide range of environments that allow for post-synthetic modifications and functionalization. This tunability of MOFs has given way to the development of exceptional electrocatalyst that can have comparable performance to noble metals, and mitigate the issues found in them.2

In this study we investigated the OER performance of the zirconia-based MOF, UiO-66, as a support for metal oxides such as CoOx, MnOx and TiOx. UiO-66 has previously been used as a support for catalyst such as molybdenum, and has rendered comparable catalytic performance to that of platinum carbon for the hydrogen evolution reaction (HER).3 Having a MOF support for catalysts, such as metal oxides, can be ideal due to the well-defined MOF surrounding that will allow them to function as catalyst, but protect them from agglomeration at high temperatures.

We synthesized samples containing UiO-66, graphene oxide (GO) and cobalt oxide (CoOx) using the solvothermal method. Electrochemical characterization revealed that the hybrid CoOx@UiO-66/GO affords an excellent catalytic activity for OER with an onset potential of 1.6 V versus RHE, comparable to that of Ir and Ru-based catalysts.2 Additionally, this study contains discussions on the factors of the high OER activity through a series of physical characterizations of the hybrid catalyst.

References:

Lee, Y., Suntivich, J., May, K. J., Perry, E. E. & Shao-Horn, Y. Synthesis and Activities of Rutile IrO 2 and RuO 2 Nanoparticles for Oxygen Evolution in Acid and Alkaline Solutions. doi:10.1021/jz2016507

Aijaz, A. et al. Co@Co3O4 Encapsulated in Carbon Nanotube-Grafted Nitrogen-Doped Carbon Polyhedra as an Advanced Bifunctional Oxygen Electrode. Angew. Chemie - Int. Ed.
55, 4087–4091 (2016).

Yang, J. et al. Porous Molybdenum Phosphide Nano-Octahedrons Derived from Confined Phosphorization in UIO-66 for Efficient Hydrogen Evolution. Angew. Chemie - Int. Ed.
55, 12854–12858 (2016).
Spray Pyrolyzed High Surface Area Ni-Based Hydrogen Evolution Electrocatalysts for AEM Electrolyzer Applications
Authors: Washington Christian , Rockward Tommy , Martinez Ulises
Published: February 2020

The most widely used hydrogen evolution electrocatalyst for alkaline electrolyzer applications is Ni. However, in order to achieve desired rates of hydrogen generation, large amounts of Ni are required. High surface area Ni electrocatalysts are typically obtained via the caustic leaching of Ni-Al mixtures to obtain Raney Ni. While this process is relatively inexpensive, thick electrodes are needed to ensure enough active surface areas. In this work, an alternative approach for the synthesis of unsupported high-surface-area Ni-based electrocatalysts via spray pyrolysis will be presented. This versatile technique allows the fine-tuning of particle morphology for controlled synthesis of materials with high purity and uniform composition. Furthermore, the promotion effect of rare-earth metal oxides (REO) on the electrochemical activity of Ni electrocatalysts will be studied for rare-earth atomic compositions of 0-10%. Increased surface area of Ni-REO electrocatalysts will be obtained by producing a solute concentration gradient using low melting point precursors, resulting in hollow catalyst particles during the evaporation process. Synthesized catalyst materials will be characterized using XRD for crystallography and phase composition, XPS for elemental catalyst surface composition, electron microscopy (SEM, TEM) for micro and nano-sized morphology, and pore size analysis (BET and PSD). Physical/chemical characterization will be correlated to the observed electrocatalytic activity for the hydrogen evolution reaction (HER) in alkaline electrolytes to better understand the co-catalyst effect of REO on the Ni HER activity.
(Invited) Recent Advances in Fuel Cell Electric Vehicle Technologies of Hyundai
Authors: Hong Bo Ki , Kim Sae Hoon
Published: February 2020

Over the past few decades, fuel cell electric vehicles (FCEVs) powered by hydrogen have received great attention as a promising candidate for not only eco-friendly vehicles due to their high power density and zero emission features, but also distributed power plants and active air cleaners on the road. Since Hyundai’s deployment of the world’s first mass-produced FCEV, Tucson ix35, in February 2013, Hyundai has been exerting every effort in resolving three major challenges, i.e., performance, durability, and cost. As a result, Hyundai unveiled an advanced FCEV, NEXO, in March 2018 and began to manufacture it for the world market. The NEXO FCEV has achieved significant technological advancements in comparison with its predecessor, Tucson ix35 model: enhanced driving range on a single charge by approximately 45%, i.e., from 415 km to around 600 km according to the fuel economy test results in Korea; improved durability from 4 years/80,000 km to 10 years/160,000 km; enhanced cold start-up capability from -20 oC down to -30 oC; improved system efficiency from 55% to 60%. In this presentation, the recent advances and progress of Hyundai’s FCEV technologies will be addressed, along with the research and development roadmap of the next-generation FCEVs aiming for more robust and cost-effective systems.
(Invited) Japan’s Current Policy and Activity Toward Realizing a Hydrogen Based Society
Authors: Ohira Eiji
Published: February 2020

The presentation shows Japan’s challenge to realize hydrogen based society including up to dated policy, market information, and RD&D activities.

To tackle several social agendas such as energy security, climate change, etc. Government of Japan has been strongly promoting activity toward realizing hydrogen based society. On December 26, 2017, the Japanese Government concluded the “Basic Hydrogen Strategy” to accomplish a world-leading hydrogen-based society.

The strategy shows future visions toward 2050 and also serves as an action plan to accomplish the visions by 2030. The strategy sets a goal that Japan should reduce hydrogen costs to the same level of conventional energy and to achieve the goal, provides integrated policies across ministries ranging from hydrogen production to utilization under the common goals.

Fuel cell applications has been penetrated to Japanese market. Total installation number of residential fuel cell has reached over 250,000. About 2,200 fuel cell vehicles have been sold and 100 hydrogen refueling stations have been operated.

To enhancing utilization of hydrogen technology, the New Energy and Industrial Technology Development Organization (NEDO) has been conducting comprehensive technology development and demonstrative research programs. The most recent result from NEDO’s program on fuel cell technology will be addressed. Also current status of NEDO’s demonstration project on hydrogen gas turbine, large scale hydrogen supply chain, power to gas will be introduced. In addition, NEDO has been developing a technology roadmap on hydrogen and the roadmap will be introduced.
(Invited) Next Generation of Nanostructures, Electrodes, and Key Components for PEM Water Electrolyzers
Authors: Carmo Marcelo , Müller Martin , Burdzik Andrea , Keeley Gareth , Scheepers Fabian , Shviro Meital , Stähler Markus , Stolten Detlef
Published: February 2020

The future of energy conversion and storage is expected to rely on the production and storage of hydrogen using water electrolyzers. In this scenario, water electrolyzers will play a key role in the establishment of an energy matrix based on renewable but intermittent power sources (e.g. wind turbines and photovoltaics). Hydrogen has the potential to drive multiple revenue streams like transportation, chemicals, green production of fertilizers, regeneration of electricity through fuel cells, and also initially supplement the energy gap through methanation. Moreover, the production, storage, or distribution can be chosen to be centralized or decentralized, and is recognized as the only option to store multi-GWh electricity. 1

In order to meet the future demand for water electrolyzers, investment and operational costs still have to be reduced. It is also crucial to develop electrolyzers that are able to operate at high current densities, variable partial load, overload, and on/off conditions. These requirements usually place PEM water electrolysis as an optimal alternative to couple with intermittent power sources. In any case the high costs of PEM water electrolysis components (based on Pt, Ir, and Ti components) are still hampering its large-scale commercial application.2

Though consistent R&D we aim to drastically reduce the costs and increase the efficiency of PEM water electrolyzers. By using advanced methods to design and characterize nanostructures and catalyst coated membranes, and by properly accessing the performance and durability of cell and stack components, we hope to be able to demonstrate in the next years the next generation of PEM water electrolyzers, and its future incorporation into our energy matrix for energy storage and conversion.
Ni-Fe Oxide Quantum Dots Anchored on Carbon Nanotubes As a Catalysts for Oxygen Reduction/Evolution Reactions for Metal-Air Batteries
Authors: Xu Nengneng , Wang Yu-Dong , Zhou Xiao-Dong , Qiao Jinli
Published: February 2020

Metal-air batteries, such as zinc-air batteries and magnesium-air batteries, can potentially enable a widespread implementation of clean renewable energy. The primary limitations of metal-air battery are the sluggish electrocatalytic kinetics on the air side and poor stability of electrode performance. Hence, highly efficient and stable Fe/Ni-based electrode can simultaneously address these challenges. In this work, a novel ORR and OER catalyst, NiFe2O4 quantum dots (QDs) is synthesized, which are self-assembled on carbon nanotubes (CNTs). A composite of NiFe2O4(QDs)/CNTs exhibits a superior bifunctional oxygen electrocatalytic activity with a low the potential gap between ORR and OER (ΔE: 0.9 V). The NiFe2O4(QDs)/CNTs electrode displays a high power density and a high specific capacity in both zinc-air batteries and magnesium-air batteries at ambient conditions. Particularly, the rechargeable zinc-air batteries show a low charge-discharge voltage gap of only 0.62 V and long-term rechargeability for more than 800 hours. The remarkable performance of NiFe2O4(QDs)/CNTs can potentially facilitate the largescale implementation of renewable energy storage by rechargeable metal-air batteries.

Keywords: NiFe2O4 quantum dots, ORR, OER, Low voltage gap, Metal-air battery
Improvement of Cathode Materials for Proton Conducting Intermediate Temperature Solid Oxide Fuel Cells
Authors: Sun Shichen , Cheng Zhe
Published: February 2020

Proton conducting oxides such as BaZr0.1Ce0.7Y0.1Yb0.1O3 (BZCYYb) are attractive electrolyte materials for intermediate temperature (~400-600oC) solid oxide fuel cells (IT-SOFC) due to their higher ionic conductivity at intermediate temperature range compared to widely-used oxide-ion conducting oxides (e.g. Yttria-stabilized zirconium, YSZ) that are used in conventional high temperature (>700oC) SOFC. Whether proton conductivity also offers additional benefit for the cathode process has not been well-studied yet. In this study, two most promising cathode materials for oxide ion conducting IT-SOFC - Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) and SrCo0.8Nb0.1Ta0.1O3−δ (SCNT) as well as their corresponding composites with proton conducting electrolyte (i.e., BSCF-BZCYYb and SCNT-BZCYYb) are evaluated as the cathode for proton conducting IT-SOFC using electrolyte supported cell structured from 750oC to 450oC. Comparisons have been made based on electrochemical impedance spectroscopy (EIS), current-voltage characteristics (IV) tests, as well as microstructure features. The implications from these studies are discussed and the directions for designing new proton conducting IT-SOFC cathodes with further improved performance are pointed out based on the insights gained from these studies.
Conversion Materials and Performance in Laser Based Light Sources
Authors: Raukas Madis , Lenef Alan , Kelso John , Engl Moritz
Published: February 2020

We briefly review the rationale and basic principles behind light sources based on (solid state) lasers and luminescence conversion, along with main applications and market need considerations for such sources (examples: medical, information projection, automotive and general lighting). It is clear that the efficiency of high luminance laser pumped phosphor sources depends strongly on the performance of conversion material which is often pushed to optical and thermal limits. Critical materials characteristics and physical mechanisms that control overall source performance will be discussed, also the expected interplay of material characteristics and laser conversion performance. We have separated contributions from thermal and non-thermal quenching mechanisms, and point out the distinction between the true loss mechanisms (e.g. Auger-like or excited state absorption related) and the decline in converted light output due to increased transparency for the pump light (due to activator ground state depletion). The main challenges and roadblocks for improving both the converter materials as well as laser sources are considered and outlook on future discussed: where is the laser based lighting expected to continue from here?
Effect of Adding Electrolyte on Current Efficiency for Light-Emitting Electrochemical Cell Using Ruthenium Complex
Authors: Aoki Atsushi , Tanaka Akebono
Published: February 2020

Organic light emitting diodes (OLED) have been greatly investigated for application in flat panel display and light source. A different type of OLED is light emitting electrochemical cell (LEC), which consists of luminescent chromophore films with solid electrolyte such as ionic ruthenium complex film. Driving process of LEC is different from that of OLED. That is, upon applied voltage, the electric double layer is formed at the interface between the anode or cathode and ionic luminescent film and hole and electron are injected from both electrodes into the luminescent film and then light is emitted by charge recombination. Thus, LEC has attractive features which are single-layer device and no requirement to use low work function metal as a cathode. However, LEC has some drawback which is ill charge-injection balance between hole and electron caused by the difference in ion size between large ruthenium complex cation and small counter anion. To improve the charge-injection balance, incorporation of small cation into ionic luminescent layer will be expected. In this study, current efficiency for LEC was improved by introduction of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as additive electrolyte into the ruthenium complex film of LEC. LEC was prepared by spin-coating tris(2,2’-bipyridyl) ruthenium(II) complex TFSI2 (Ru(bpy)3(TFSI)2) and poly(methyl methacrylate) (PMMA) matrix in acetonitrile solution with LiTFSI solid electrolyte on ITO anodes. And then silver was vacuum-deposited onto the resulting ruthenium complex film with solid electrolyte on ITO anodes. The luminescent property of LEC was performed by applying constant current. The standard LEC without LiTFSI was not emitted and the lower voltage than 1 V was observed in the constant current of smaller than 1.5 mA whereas it was emitted and the voltage of around 2.5 V was observed in the constant current of larger than 1.5 mA. These results indicate that the only hole injection occurs and the electron injection does not occur until the applied current over 1.5 mA. It’s due to the thicker electric double layer of ruthenium complex at the cathode of LEC. As introduction of LiTFSI into the ionic luminescent layer, the emission starts at the smaller applied current with increasing amount of LiTFSI. The maximum current efficiency becomes 3.0 cd/A in the LEC containing 3 wt% LiTFSI. However, the addition of more than 3 wt% LiTFSI into LEC makes LEC performance worse because the distance between ruthenium complex become wide and the electron hopping rate becomes slow. Finally, addition of 10 wt% LiTFSI makes crystalize ionic luminescent layer and it does not function as LEC. Therefore, we found that the introduction of 3 wt% LiTFSI to LEC was the optimum condition.
Comparative Study between Pulsed-Voltage and Pulsed-Current Driving for Enhanced Stability of Electrochemiluminescent Device
Authors: Shin Ik-Soo , Kang Moon Sung
Published: February 2020

Light-emitting device based electrochemiluminescent (ECL) process promises cost-efficient, large-area emissive applications, as its electrochemical characteristic enables use of air-stabile electrodes and single-layered emitting material. However, rapid degradation of its performance along with thermal decomposition of the device has proven a seemingly fundamental problem. Herein, we present a novel approach that overcomes this critical issue showing that the pulsed current operation regarding electrochemical redox kinetics on the surface of electrode should be considered in order to minimize undesired side reactions. By designing and operating solution-based ECL devices, we confirm the basic principles and conditions for stable performance of the ECL device. It is also demonstrated that applying a controlled-current pulse instead of controlled-voltage yields enhanced stability of ECL devices yielding a half-life time for > 2,000 sec. Bis (2-phenylquinoline) iridium (III) picolinic acid was employed as an ECL luminophore, and the devices were analyzed under various operating conditions; controlled-voltage or controlled-current pulses were applied to the device at different magnitude, frequency, and duty cycle.
Novel Red-emitting Phosphors: Synthesis, Photoluminescence and Theoretical Calculations
Authors: Liu Wei-Ren
Published: February 2020

A series of novel red-emitting Sm3+-doped phosphors were synthesized by a conventional solid state reaction. The crystal structure and atomic coordinates of was characterized by Rietveld refinement. Luminesce properties of as-synthesized Sm3+-doped phosphors are carried out by PL/PLE, decay life time, thermal quenching as well as reflectance spectrometer and LED fabrications. The results indicate that composition-optimized phosphor exhibits orange-red emission peaks located on 564, 601, 608 and 648 nm attributed to the transitions of 4G5/2 → 6H5/2, 4G5/2 → 6H7/2, 4G5/2 →6H7/2

and 4G5/2 → 6H9/2, respectively. The results of LED fabrication by combing 380 chip and blue/green phosphors are demonstrated in this study. Finally, from viewpoint of theoretical calculations, band structure and density of state for host and Sm3+-doped phosphor are studied by first principles calculations. All the results indicate that our phosphors could be a potential material for white light-emitting diodes.

FIG. 1 (a) Electroluminescence spectrum of BaMgAl10O17:Eu2+, Ba2SiO4:Eu2+ and as-synthesized red phosphor with 380 chip. Inset: photo image of LED device derived at 20 mA; (b) CIE coordinates of red phosphor excited at 365 nm. Inset: red phosphor image in UV box under 365 nm excitation.

References

[1] Irish Valerie B. Maggay, Kai-Yuan Yeh, Bingfu Lei, Mikhail G. Brik, Michal Piasecki and Wei-Ren Liu,* “Luminescence properties of Eu2+ - activated NaCaBeSi2O6F for white light-emitting diode applications,” Mater. Res. Bull.,
100, 26-31 (2018).

[2]Chun-Ting Chen, Maxim S. Molokeev, Tzu-Jen Lin and ± “Synthesis, luminescent properties and theoretical calculations of a novel orange-red-emitting Ca2Y8(SiO4)6O2:Sm3+ phosphors for white light-emitting diodes applications,” Dyes and Pigments, 150, 121-129 (2018).

[3] Jy-Chern Chang, Haikun Liu, Pin-Chun Lin, Libing Liao and Wei-Ren Liu,* “Intense broad-band absorption and efficient blue-emitting SrCa2MgSi2O8:Eu2+ phosphor for high color-rendering white LED Applications,” J. Alloy and Compds., in press.