bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-Index Faceted Platinum Nanoflowers Catalysts for Proton Exchange Membrane Fuel Cell
Authors: Abdelhafiz Ali , Liu Meilin 
Published: February 2020

Proton exchange membrane fuel cells (PEMFCs) have tremendous potential to be the preferred power sources for many emerging technologies, from electric vehicles to portable/mobile devices and smart grids, because of their numerous inherent advantages such as high efficiency, high energy density, low emissions, and fast start-up and shut-down capability. While PEMFCs are expected to use platinum group metal (PGM)-based catalysts in the near-term, the cost of the Pt-based catalyst alone constitutes over 40% of the fuel cell stack cost. Enormous efforts have been devoted to reducing the high cost of catalyst. To date, the catalysts can be classified into three groups according to the active component used: PGM-based catalyst (supported on carbon or other supports); PGM-based catalysts that are modified or alloyed with other metals such as Cu, Co, and Ru; and PGM-free catalysts such as non-noble metals and organometallic complexes. PGM-free catalysts are attractive for cost reduction of PEMFC technology, however, in reality is still a long way to go to before they can be used to run actual fuel cell application. Here in, we are proposing a facile, one-step, synthesis of Pt-based alloy nanoparticles for cost effective low temperature oxygen reduction reaction electrocatalysis at industrial scale.
Direct Pt nanoparticles synthesis is performed under room temperature to form a branched triple and quadruple-pods particles with an average size of ~3.5 nm, as confirmed by X-ray diffraction (XRD) and Scanning transmission electron microscope (STEM) analysis. Rotating disc electrode (RDE) setup is used to probe ORR. Results showed that synthesized Pt-nanoparticles superior catalytic activity for oxygen reduction reaction compared to state of the art Pt-XC/72R commercial catalyst. Pt-nanoparticles periphery are conformed of high index family crystallographic planes, as observed by STEM analysis. High index planes contain lower density of kinks, which optimize the adsorption/desorption energies to be neither too weak nor too strong. Pt-nanoparticles under accelerated durability testing (ADT) outperform their state of the art commercial catalyst counterparts, surviving 81% of electrochemical active surface area (ECSA) after 10,000 testing cycles.
Using a catalyst coated membrane (CCM) technique membrane electro assembly (MEA) was prepared to test Pt nanoparticles under actual PEMFC operation conditions (i.e. temperature and humidity). MEA prepared using the synthesized Pt-nanoparticles outperformed their counterparts prepared by Pt-XC/72R state of the art commercial catalyst with 27% enhancement factor. The reported Pt-based nanoparticles propose a competitive and more efficient synthesis route to prepare large scale commercial catalyst without the need of sophisticated apparatus or special heating conditions.
Super-Strong Nafion/PVA/Uhmwpe Membranes for Proton and Hydroxide Ion-Exchange Fuel Cells
Authors: Li Jin , Zhang Qinghua , Li Runlai , Gao Ping 
Published: February 2020

Perfluorosulfonic acid (PFSA) ionomers have been used extensively in proton exchange membranes due to their high proton conductivity and strong electrochemical stability. However, proton and anion conductivity through the PFSA membranes are contingent upon water uptake, but high water content in the membrane causes loss of long-term durability of the fuel cell system because of the water swelling-induced reduction in membrane’s mechanical strengths. Large body of literatures are available to address these issues, for example, hydroscopic nanoparticulate fillers have been used for self-hydration of the membrane, and aligned polytetrafluoroethylene (PTFE) has been employed to reinforce the tensile strengths of the PFSA ionomer. Unfortunately, there is yet no report to date that can resolve pareto fronts issues, i.e., simultaneously having high proton conductivity and high tensile property. Besides, the cost of PFSA membranes, e.g., Nafion, is still prohibitively high. Here, we report a new and low-cost hierarchical membrane with high proton/anion conductivity, low moisture/methanol uptake and super-high tensile strengths. The new membrane is a hybridized composite structure consisting of biaxially oriented nanoporous ultrahigh molecular weight polyethylene (UHMWPE) film coated with Nafion and polyvinyl alcohol (PVA) blend. The tensile strength of the composite membrane is at least 10 times higher than that of the pure Nafion membrane when fully humidified, and the proton and alkaline conductivity is comparable to that of the Nafion/PVA blend. The nanoporous UHMWPE simultaneously acted to provide the high tensile strengths, ion-conductivity selectivity and nanoconfinement to limit the water and methanol uptake. Thus the new hierarchical Nafion/PVA/UHMWPE membrane is potentially an ideal ion-exchange membrane for low temperature hydrogen and direct methanol fuel cells.
The work is financially supported by the theme-based research project of the university grants committee of Hong Kong, Grant No. T23-601/17-R
Understanding the Influence of Porosity on Product Selectivity for Copper CO2 Reduction Electrocatalysts
Authors: Fritz Kevin Eugene , Wiesner Ulrich , Suntivich Jin 
Published: February 2020

The carbon dioxide reduction reaction (CO2RR) provides a process for producing valuable chemicals and energy-dense fuels from CO2; however, selectively producing a specific high-value product remains challenging. In this contribution, we present our study on how to harness nanoporous morphologies to address this challenge. Our work is driven by several results in literature which have now established that nanoporous morphologies can affect the CO2RR product distribution on Cu catalysts (1-3). To gain insight into this effect, we use model nanoporous Cu catalysts prepared using a self-assembled block copolymer (BCP) template. The BCP-template approach allows precise control over pore size and geometry as well as thickness. Using these structures and the dependence of the product distribution on pore sizes, pH, and mass transport, we will discuss the influence of nanoporous morphologies on the CO2RR efficacy and the implications for future CO2RR catalyst design, particularly within the context of reaction intermediate trapping for selectivity towards high-value products.

References

(1) A. Dutta, M. Rahaman, N. C. Luedi, M. Mohos, and P. Broekmann, ACS Catal.,
6(6), 3804 (2016).
(2) K. D. Yang, W. R. Ko, J. H. Lee, S. J. Kim, H. Lee, M. H. Lee, and K. T. Nam, Angew. Chem. Int. Ed.,
56(3), 796 (2017).
(3) T. Kim, A. Kargar, Y. Luo, R. Mohammed, E. Martinez-Loran, A. Ganapathi, P. Shah, and D. P. Fenning, ACS Appl. Energy Mater.,
1(5), 1965 (2018).
Developing and Understanding BiFeO3 Photoelectrodes for Solar Water Splitting
Authors: Radmilovic Andjela , Choi Kyoung-Shin 
Published: February 2020

Hydrogen production by photoelectrochemical water splitting is a challenging and exciting research topic that continues to receive much attention as it is a promising option for meeting the global energy demand. For this technology to compete with fossil fuels, a solar-to-hydrogen (STH) efficiency above 10% must be achieved using an inexpensive and durable photoelectrochemical cell (PEC). Accordingly, our group has been investigating oxide-based photoelectrodes that can be produced via practical solution-based syntheses using inexpensive raw materials. We are specifically interested in developing ternary oxides, which provide more opportunities to tune the composition and atomic/electronic structures of the photoelectrode materials relative to their corresponding binary oxides.
In this presentation, the synthesis and investigation of BiFeO3 photoelectrodes will be discussed. BiFeO3 has a bandgap of ~2.2 eV and appropriate band positions for water splitting; however, it has not been extensively studied for photoelectrochemical applications. BiFeO3 has previously shown both n-type and p-type behavior, meaning it can serve as either a photoanode for water oxidation or photocathode for water reduction, respectively. Here, we will first introduce electrochemical methods to prepare high-quality n-type and p-type BiFeO3 films. We will then discuss the photoelectrochemical properties of the resulting films and present strategies to further optimize the performance of BiFeO3 as both a photoanode and photocathode for use in a water-splitting PEC.
(Keynote) Stable Mixed-Anion Photocatalysts for Visible-Light-Induced Water Splitting
Authors: Abe Ryu 
Published: February 2020

Photo-induced water splitting using semiconductor photocatalysts has attracted considerable attention for producing H2 as a clean energy carrier, while the effective utilization of visible light is imperative to achieve the desired efficiency for practical applications.[1, 2] Recently, mixed-anion compounds such as oxynitrides have been intensively studied as promising candidates since one can expect that higher energy p orbitals of non-oxide anions (e.g., N-2p) elevate their valence band maximum (VBM) values. Unfortunately, most of them are subject to facile self-oxidation by photogenerated holes, while highly dispersed cocatalyst particles certainly improve the stability of some oxynitrides.[3] We have recently demonstrated that Sillén–Aurivillius type perovskite oxyhalides such as Bi4NbO8Cl can stably and efficiently oxidize water to O2 under visible light without any surface modifications, and also exhibits a stable Z-scheme water splitting when coupled with a H2-evolving photocatalyst.[4] It was revealed that the VBMs of these materials consist mainly of O-2p orbitals, instead of Cl-3p (or Br-4p), but their positions are much more negative than those of conventional oxides. [5, 6] Thus, they possess narrow bandgaps for visible light absorption as well as sufficiently negative CBMs for water reduction. DFT calculation visualized a fairly strong hybridization between the Bi-6s and O-2p orbitals, which can explain why the O-2p orbitals are elevated in energy, combined with the result on Madelung site potential analysis that can rationalize the origin of high energy of O-2p orbital in these materials. Since O– anions are known to be relatively stable, photogenerated holes populated at the O-2p orbitals will not lead to self-decomposition but to oxidize water. These results could provide new strategies for developing durable photocatalytic materials for water splitting under visible light, by manipulating the interaction between post-transition metal s orbitals and O-2p orbitals.
[1] R. Abe, J. Photochem. Photobiol. C: Photochemistry Reviews, 11 (2011) 179.
[2] R. Abe, J. Tang et al., Chem. Rev. 118 (2018) 5201.
[3] R. Abe, M. Higashi, K. Domen, J. Am. Chem. Soc., 132, (2010) 11828.
[4] H. Fujito, H. Kunioku, H. Kageyama, R. Abe et al., J. Am. Chem. Soc., 38 (2016) 2082.
[5] D. Kato, H. Kunioku, R. Abe, H. Kageyama et al. J. Am. Chem. Soc., 139 (2017) 18725.
[6] H. Kunioku, H. Kageyama, R. Abe et al., J. Mater. Chem. A, 6 (2018) 3100.

Key Words: Photocatalyst, Semiconductor, Water splitting, Solar energy
(Invited) Structure, Composition, Support, and Electrolyte Effects in CO2 Electroreduction
Authors: Roldan Cuenya Beatriz 
Published: February 2020

The efficient electrochemical conversion of CO2 (CO2RR) to valuable fuels and feedstocks is a highly sought process towards the minimization of the carbon footprint. However, higher selectivity towards C2+ products must be achieved before a broad industrial use can be envisioned. Better efficiency can be attained by tuning the morphology (size, shape, dispersion), oxidation state, composition of the catalysts, NP/support interactions, and by a rational selection of the electrolyte. In addition, understanding the changes that a catalyst may experience on its surface during a reaction is crucial in order to stablish structure/composition-reactivity correlations. Here, mechanistic insight into CO2RR will be provided by using as target materials size- and shape-controlled mono and bimetallic NPs including Cu, Cu2O, Zn, Cu-M (M=Zn, Co, Pd, Ag, Au) NPs with spherical and cubic shapes as well as Cu2O cubes decorated with monodispersed M nanoparticles on the surface.
A synergistic combination of spectro-electrochemical methods, in situ microscopy (EC-AFM), operando X-ray absorption spectroscopy (XAS) and quasi in situ X-ray photoelectron spectroscopy (XPS) were used to gain insight into the morphological, structural, and chemical transformations underwent by the NPs during CO2RR. I will illustrate that the as-prepared state of the mono and bimetallic NPs is drastically different from the structure and surface composition of the working catalyst.
Design of Materials for Electroreduction of Nitrogen to Ammonia: A Computational Perspective
Authors: Matanovic Ivana , Garzon Fernando H 
Published: February 2020

Theoretical studies and computational modeling play a key role in predicting various properties of catalytic materials, including their activity and selectivity towards a desired electro-catalytic pathway. In the last decade, density functional theory calculations have been used to study the activity and selectivity of various materials for the nitrogen electroreduction, an extremely important aspect in the development of novel technologies for the ammonia synthesis. However, the design of an ideal electro-catalyst that exhibits high activity for nitrogen reduction to ammonia while at the same time suppresses the competing hydrogen evolution reaction is still an ongoing pursuit.
Here we will use the example of molybdenum nitride and molybdenum carbide to illustrate different aspects in the design of materials for nitrogen electroreduction to ammonia and discuss different challenges associated with this effort [1, 2]. We will first present calculations of free energy diagrams and kinetic volcano plots aimed at understanding the activity of different surfaces of the molybdenum nitride (Mo2N) and molybdenum carbides (MoC and Mo2C) towards hydrogen evolution reaction and nitrogen electroreduction to ammonia. Secondly, we will discuss the thermodynamics calculations directed towards understanding the stability of these materials at different cell potentials and pH. Namely, our results show that at the nitrogen reduction potentials the catalytic surface can be covered with the H-adatoms rather than the N-adatoms. In addition, the carbides and nitrides can be converted to oxynitrides or oxides, which can lead to the decrease in the activity and durability of the catalytic material. Molybdenum carbides and nitrides will be used to illustrate how computational modeling can direct the design of the active sites with highest efficiency for nitrogen reduction to ammonia, but also support the optimization of reaction conditions to ensure the catalyst durability.
[1] I. Matanovic, F. H. Garzon, and N. J. Henson, Electro-reduction of Nitrogen on Molybdenum Nitride: Structure, Energetics, and Vibrational Spectra from DFT, Phys. Chem. Chem. Phys. 2014, 16: 3014-3026.
[2] I. Matanovic and F. H. Garzon, Nitrogen Electroreduction and Hydrogen Evolution on Cubic Molybdenum Carbide: A Density Functional Study, Phys. Chem. Chem. Phys. 2018, 20: 14679-14687.
Electrochemical Synthesis of Ammonia Using Origami-like Molybdenum Carbide Nanoflakes As Nitrogen Reduction Reaction Catalyst
Authors: Ramaiyan Kannan Pasupathikovil , Ozden Sehmus , Maurya Sandip , Komini Babu Siddharth , Benavidez Angelica D , Garzon Fernando H , Kim Yu Seung , Mukundan Rangachary , Kreller Cortney R. 
Published: February 2020

Ammonia plays a crucial role in feeding the majority of today’s population and its production has increased from a few thousand tons per year in 1908 to above 100 million tons per year today, revolutionizing the fertilizer industry thanks to the Haber-Bosch (HB) process. However, the HB process is highly energy intensive consuming about 1.4 % of the fossil energy generated worldwide and releasing 1.87 tons of the greenhouse gas CO2 into the environment per ton of ammonia synthesized. Hence, finding alternative and energy efficient ways to synthesize ammonia under milder conditions is important from more than one perspective. The challenge associated with NH3 synthesis from its constituent nitrogen and hydrogen gases is breaking the strong N≡N bond (947 kJmol-1). While heterogeneous catalytic synthesis needs high temperature and pressure operation, electrochemical synthesis routes offer a milder approach. However, electrochemical synthesis of ammonia under different temperatures, utilizing different electrolytes and catalysts has not yet reliably produced ammonia at viable rates and efficiencies. We report a Mo2C cathode catalyst for ammonia synthesis that has demonstrated synthesis rates on the order of 2x10-12 molcm-2s-1 for more than 24 hours at 30 °C using Nafion 212 as the electrolyte and Pt/C as the anode. The β-Mo2C has a hexagonal lattice structure with an origami-like morphology containing numerous kinks which may improve its electrocatalytic activity. The maximum synthesis rate was obtained at -0.5 V, however, the faradaic efficiency decreased with increasing over-potential. This catalyst offers a promising alternative for producing ammonia especially with electrolytes that conduct protons under dry conditions. This presentation further covers the utility of Nafion as an electrolyte for electrochemical ammonia synthesis.
References
1. P. Ramaiyan, M. Sandipkumar, A. D. Benavidez, S. K. Nayak, Y. S. Kim, F. H. Garzon, R. Mukundan, C. R. Kreller, Meeting Abstracts 2018, MA2018-01 2012 1.
2. D. Benavidez, S. K. Nayak, E. Coker, F. H. Garzon, Meeting Abstracts
2018, 1.
3. Matanovic, F. H. Garzon, Phys Chem Chem Phys 2018, 20, 14679.
Removal of Nitrate and Ammonia from Wastewater
Authors: Bagheri Hariri Mohiedin , Botte Gerardine G. 
Published: February 2020

Ammonia and nitrate contamination of groundwater, surface water, and other water resources is considered a serious environmental and human health issue that causes several problems like algae bloom, fatal illnesses specially for the infant under 6 months. Electrochemical techniques for ammonia oxidation and nitrate reduction reactions are usually straightforward, energy-efficient, environmentally-friendly, and easy to control.
Electrochemical techniques for separate removal of ammonia and nitrate has been extensively studied. However, in this work, we demonstrate a new process that addresses both water pollutants simultaneously in a single cell that leads to a considerable energy saving in the order of 90 % and 35-65 % less energy per grams of ammonia and nitrate removal, respectively. A new flow cell with novel electrode architectures is introduced to perform both ammonia/nitrate removal simultaneously. The concentration of nitrate and ammonia were measured according to the Environmental Protection Agency (EPA) standards which is a UV-vis spectrophotometric based technique, and ammonia Ion Selective Electrode (ISE-THERMO), respectively. Effect of electrode loading and other process variables on the ammonia and nitrate removal rates were evaluated. Findings of this work will be presented at the meeting.
Direct Ammonia-Fueled Solid Oxide Fuel Cells
Authors: Tao Greg 
Published: February 2020

Ammonia, as a hydrogen carrier, has a much higher volumetric energy density than hydrogen and can be safely handled and distributed in a liquid form at an ambient temperature with a pressure greater than 1MPa. Similar to hydrogen, a clean-burning ammonia potentially can be used for power generation with zero greenhouse gas emissions. A Solid Oxide Fuel Cell (SOFC), typically operating at a temperature of 700ºC – 900ºC, has been widely acknowledged by the R&D society for a direct conversion of chemical energy of fuels (e.g. hydrocarbon fuels, ammonia, etc.) into electricity at a proven efficiency as high as 60%. Lowering the SOFC operating temperature to 700°C or below potentially enables considerable cost reduction with opportunities of using inexpensive materials for constructing SOFC systems that otherwise could not be considered. However, the corresponding SOFC inevitably faces challenges of higher electrode polarization losses and electrolyte ohmic losses, as well as reduced electrode catalytic activities.
Chemtronergy is actively pursuing the development of the anode-supported SOFC technology capable of operating directly on the ammonia fuel at a temperature below 650ºC for reliable power generation. This talk will cover discussions of cell materials design and ammonia catalyst consideration for the mitigation of the increased polarization losses and ammonia reaction with the nickel-based anode, respectively, caused by lowering operating temperatures. Materials implementation and validation on both button cells (2 cm2) and single cells (100 cm2) over time will also be presented.
(Invited) Low Ionic Resistance Radiation-Grafted Cation- and Anion-Exchange Membranes for Reverse Electrodialysis (salinity gradient power) Application: Cross-Linking Is Essential for High Permselectivities.
Authors: Willson Terry , Bance-Soualhi Rachida , Hamerton Ian , Varcoe John R. 
Published: February 2020

Reverse electrodialysis (RED) cells are a form of salinity gradient power technology where electrical energy can be recovered from the mixing of waters of differing salinities. RED cells require both cation- and anion-exchange membranes (CEM and AEM, respectively) in order to operate.
This presentation details the development of radiation-grafted (RG) CEMs and AEMs, which were evaluated for ex situ resistances (conductivities) and permselectivities. Trends between ex situ properties will be discussed (e.g. room temperature Na+ conductivities (in water) are higher with RG-CEMs that possess higher gravimetric water uptakes, see Figure).
It is clear that RG-CEMs and RG-AEMs are desirably low resistance. However, non-crosslinked RG-CEMs and RG-AEMs have permselectivities that are too low for application in RED cells. However, the addition of crosslinking (either via the addition of divinyl-monomers, such as BVPE, or through the use of difunctional amination agents, such as N,N,N',N'-tetramethylhexane-1,6-diamine) leads to higher permselectivity types.
Therefore, we conclude that cross-linking is essential for the production of RG-ion-exchange membranes with high permselectivities for such application.

Figure 1