bluuebunny/crossref_metadata_2025 huggingface dataset:
Study the Activity of a Novel Ni-Based Electrocatalyst for Oxygen Evolution Reaction in Alkaline Media
Authors: Ghahremani Raziyeh , Staser John A.
Published: February 2020

Electrocatalytic water splitting into hydrogen and oxygen has a great potential to produce hydrogen as a carbon neutral source of energy. However, the sluggish kinetics of oxygen evolution reaction (OER) leads to an inefficient process prohibiting industrial application [1]. Therefore, highly efficient OER electrocatalysts are needed to reduce the energy barrier and enhance the efficiency of water electrolysis cell [2]. IrO2 and RuO2 are the most efficient electrocatalysts for OER, however their commercial industrial applications are limited due to their high cost and low earth abundance. To address this issue, several non-noble metal based OER electrocatalysts including transition metal oxide/hydroxides, perovskite, and molecular electrocatalysts have been developed [3]. Among them, Ni-based materials attract substantial attention owing to their low cost, high corrosion stability, and remarkable catalytic activity in alkaline media. The present work aims to evaluate and compare the electrochemical activity of a novel Ni-based electrocatalyst prepared from two different plating baths toward OER. Electrochemical measurements including cyclic voltammetry (CV), quasi-steady state polarization (QSSP), electrochemical impedance spectroscopy (EIS), and chronopotentiometry (CP) were carried out to study and compare the activity, charge transfer resistance and stability of different electrocatalysts developed in this study toward OER in alkaline media.

References

[1] X. Su, Q. Sun, J. Bai, Z. Wang, C. Zhao, Electrodeposition of porous MoO42--doped NiFe nanosheets for highly efficient electrocatalytic oxygen evolution reactions, Electrochimica Acta. 260 (2018) 477–482.

[2] X. Lu, C. Zhao, Electrodeposition of hierarchically structured three-dimensional nickel–iron electrodes for efficient oxygen evolution at high current densities, Nat. Commun. 6 (2015) 6616.

[3] M. Lee, H.-S. Oh, M.K. Cho, J.-P. Ahn, Y.J. Hwang, B.K. Min, Activation of a Ni electrocatalyst through spontaneous transformation of nickel sulfide to nickel hydroxide in an oxygen evolution reaction, Appl. Catal. B Environ. 233 (2018) 130–135.
Three-Dimensional CoS2-MoS2 Hetero-Nanosheets Architecture from Polyoxometalate for Highly Efficient Electrocatalytic Hydrogen Evolution
Authors: Lei Jie , Bizuneh Girum G. , Zheng Mingsen , Dong Quanfeng
Published: February 2020

Electrolytic water splitting for hydrogen production, especially driven by renewable energy inputs such as wind and solar, stands out as a promising alternative technology for clean energy. By far, the state-of-the-art electrocatalysts for HER are platinum (Pt)-based catalysts. The wide practical applications are thus restricted due to their global scarcity and exorbitant cost. Increasing research attention has been attracted to the non-precious metal-based catalysts, such as transition metal sulfides, phosphides and oxides with promising good catalytic activity and durability for HER. Significantly, the transition metal sulfides electrocatalysts, such as MoS2, WS2, CoS2, Ni2S3, have presented superior HER performance which are attributable to the exposed edge active sites. To further enhance the catalytic activity, many strategies have been successfully developed to construct abundant active sites and increase electrical conductivity, such as doping heteroatom, constructing heterostructure with composite metal sulfides.

In the present study, three-dimensional CoS2-MoS2 hetero-nanosheet arrays grown on carbon cloth (CC) were successfully synthesized from an Anderson polyoxometalate (NH4)3[H6CoMo6O24] as the precursor. Benefiting from the heterostructure with abundant edge active sites, the composite exhibits superior activity with overpotentials of 177 mV for the HER at a current density of 10 mA cm-2 in 0.5 M H2SO4 aqueous electrolyte (Figure 1).

Figure 1
Bifunctional PGM-Free Hydrogen Evolution and Oxidation Electrocatalysts for AEM Electrodes
Authors: Serov Alexey , Lubers Alia , McKinney Samuel , McCool Geoffrey , Romero Henry , Odgaard Madeleine , Kendrick Ian , Pann Serge , Mukerjee Sanjeev , Capuano Christopher B , Ayers Kathy , Zulevi Barr
Published: February 2020

Anion Exchange Membrane Fuel Cells (AEMFCs) are a developing alternative to Proton Exchange Fuel Cell (PEMFC) technology. A great advantage of this technology is the possibility of replacing PGM catalysts on both anode and cathode and therefore reducing the costs. For example several PGM-free electrocatalysts have demonstrated superior fuel oxidation performance[1]. In AEM electrolysis both Hydrogen [2] and Oxygen Evolution[3] PGM-free catalysts have been demonstrated. In the present work we present unprecedented performance of a Nickel-based Hydrogen Evolution (HER) catalysts that are bifunctional for the Hydrogen Oxidation (HOR) reaction. These Nickel-based catalysts are multifunctional catalytic systems and rely on g alloying and mixed and low-coverage complementary metal oxides to fine tune surface-electrochemical interactions and reactions. While the goal of the work is to create reversible HER/HOR PGM-free catalysts, the efforts to date were focused on making the most active nickel-based bifunctional HER and HOR catalysts. Next reversible electrodes will be developed and catalyst stability under HER/HOR mode switching will be tested. (ARPA-E OPEN 2015 DE-AR0000688)

A series of nickel-based catalysts were synthesized to create mixed Nickel-alloys and oxides that promote the activation of water and hydroxyl groups on the catalysts. A range of wet-chemical routes was used to produce carbon-supported NiMo, NiCu, and NiMoCu supported on a range of standard and novel Interconnected Mesoporous Carbon™ supports. The materials were characterized through physical parameters such as crystal phase, size, and surface chemistry using XRD, XPS, and Raman Spectroscopy. These materials were evaluated in membrane electrode assemblies [MEAs] using a variety of membranes and ionomers. Unprecedented PGM-free HER performance exceeding 1000 mA/cm2 @ 1.9V and HOR performance exceeding 300 mA/cm2 @ 0.65V were achieved. Reversible MEA structures for these catalysts are still being optimized.

References

[1] U. Martinez, et al Phys. Chem. Chem. Phys. 14 (2012) 5512-5517.

[2] Bates, M. et al J Phys Chem C Nanomater Interfaces. 2015 Mar 12; 119(10): 5467–5477.

[3] Bates, M. et al ACS Catal., 2016, 6 (1), pp 155–161

Figure 1
Two-Dimensional Nanoframes for High Activity Bifunctional Acidic Oxygen Reduction and Evolution Electrocatalysts
Authors: Godinez-Salomon Fernando , Albiter Luis , Rhodes Christopher P.
Published: February 2020

Bifunctional oxygen electrocatalysts that facilitate the acidic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the same electrode are critical components of unitized regenerative fuel cells (URFCs) and metal-air batteries. Obtaining bifunctional oxygen catalysts that simultaneously provide high ORR and OER activity, high stability, and lower precious metal content remains a significant challenge. Our recent work has explored bimetallic two-dimensional (2D) nanoframes as an approach to obtain carbon-free, unsupported nanostructures and demonstrated nickel-platinum and nickel-iridium 2D nanoframes function as high activity, separate ORR and OER catalysts respectively.1,2 To obtain high activity bifunctional oxygen catalysts, we investigated the combination of NiPt and CoIr 2D nanoframes. Bimetallic 2D nanoframes were prepared by microwave-assisted synthesis of noble metal-decorated transition metal hydroxide nanosheets followed by thermal reduction and chemical leaching steps. The 2D nanoframes utilize noble metal (Pt,Ir)-transition metal (Ni, Co) interactions to alter surface electronic structure, and the unsupported nanostructure provides a carbon-free matrix with three-dimensional accessibility to the catalytically active sites. Electrochemical testing using a rotating disk electrode configuration showed the two-component 2D nanoframe bifunctional oxygen electrocatalysts have higher ORR mass activity, OER mass activity, and round-trip efficiency compared with baseline Pt-IrO2 catalysts. Accelerated durability testing consisting of repeated voltage cycles over ORR/OER potential ranges showed that the 2D nanoframe catalysts exhibit similar ORR stability and improved OER stability compared with Pt-IrO2. The ability to combine highly catalytically active surfaces within a carbon-free 3D nanoarchitecture provides the opportunity to design bifunctional catalysts with improved activity and stability.

References

Godinez-Salomon, F.; Mendoza-Cruz, R.; Arellano-Jimenez, M. J.; Jose-Yacaman, M.; Rhodes, C. P., Metallic Two-Dimensional Nanoframes: Unsupported Hierarchical Nickel-Platinum Alloy Nanoarchitectures with Enhanced Electrochemical Oxygen Reduction Activity and Stability. ACS Appl. Mater. Interfaces
2017, 9, 18660-18674. DOI: 10.1021/acsami.7b00043

Godínez-Salomón, F.; Albiter, L.; Alia, S. M.; Pivovar, B. S.; Camacho-Forero, L. E.; Balbuena, P. B.; Mendoza-Cruz, R.; Arellano-Jimenez, M. J.; Rhodes, C. P., Self-Supported Hydrous Iridium–Nickel Oxide Two-Dimensional Nanoframes for High Activity Oxygen Evolution Electrocatalysts. ACS Catal.
2018, 8, 10498-10520. DOI: 10.1021/acscatal.8b02171
Pt-Mn/C and Pd-Mn/C Nanoparticles As ORR Electrocatalysts
Authors: Ahmadi Mahdi , Abruña Héctor D.
Published: February 2020

The sluggish kinetics of the oxygen reduction reaction (ORR) at the cathode remains as one of the main challenges for commercial viability of alkaline exchange membrane fuel cells (AEMFCs). It is therefore, of great interest to explore the development of electrocatalysts with superior activity and stability relative to the conventional carbon supported Pt nanoparticles (NPs).

In this work we have studied the effects and evolution of structure and surface composition of Pt-Mn and Pd-Mn NPs on their electrocatalytic activity for the ORR in alkaline media. Both Pt-Mn and Pd-Mn NPs were synthesized using solvothermal methods and were supported on C via impregnation. In the case of Pt-Mn an ordered intermetallic phase was obtained by heat treatment, while for Pd-Mn NPs heat treatment did not lead to an ordered alloy. We have investigated the crystalline structure of these NPs using X-ray diffraction (XRD) and their size, morphology and composition using TEM/STEM, EELS and EDX. Cyclic voltammetry (CV) and rotating disk electrode (RDE) voltammetry were used to assess their electrocatalytic activity and stability.

The NPs were electrochemically dealloyed in acidic media, through potential cycling, leading to the formation of Pt and Pd shell on PtMn and PdMn core. The dealloyed nanocatalysts exhibited over 400% increase in mass activity and 500% increase in specific activity as compare to Pt/C. The stability of the electrocatalyst was tested after 4,000 potential cycles in alkaline media following the DOE protocol (0.6-1.0 V vs reversible hydrogen electrode). In alkaline media, Mn surface segregation ensued, leading to a lower electrocatalytic activity when compared to the freshly dealloyed catalyst.
Interface Effects and Band Edge Engineering in Photocatalytic Bi2WO6
Authors: Bainglass Edan , Huda Mohammad Nurul
Published: February 2020

Photocatalytic water-splitting is one of the most promising methods for solar-based renewable and sustainable energy applications. Ideal photocatalytic materials must be stable in aqueous solution, cost effective, and support several electronic properties for efficient device operations. These include conduction/valence band edges which straddle the H2/O2 redox potentials to achieve stochiometric reactions, a narrow band gap of 1.8 – 2.2 eV to absorb enough of the solar spectrum while retaining the driving potential for efficient charge carrier conduction, and a high band dispersion to reduce carrier recombination. The ns2
md0 metal oxide group has been suggested to favor high carrier mobility due to the dispersive ns and np characters of the valence band maxima and conduction band minima, respectively. Of these, bismuth-tungstate (Bi2WO6), a 2.6 eV n-type semiconductor, yields p-type materials as an impurity in quaternary oxides such as CuBiW2O8 and AgBiW2O8. On its own, however, Bi2WO6 exhibits high hole effective mass, or low valence band dispersion. Additionally, the band edges of Bi2WO6 experience an upshift with respect to WO3, though the conduction band of Bi2WO6 remains 0.3 eV below the H2 reduction potential, as compared to 0.5 eV in WO3. We will present results from density functional theory analyses of WO3:Bi2WO6 interfaces to better understand the behavior of Bi2WO6 at heterojunctions, as well as Sb:Bi2WO6 alloying for band gap and band edge engineering. The work is supported by NSF grant #1609811. Computations were performed on Texas Advanced Computing Center servers.
(Invited) 100MW-class vanadium flow battery projects in different applications in China
Authors: Huang Mianyan
Published: February 2020

Vanadium flow battery (hereafter referred as VFB) is one of the most suitable energy storage systems (hereafter referred as ESS) for grid-connected renewable power. And the inherent capitalization potential will improve its commercialization further in the coming future as well. However, comparing to other popular energy storage technology, VRB technology is still lack of experience on large-scale application in different situation.

As the Guideline to Promote Energy Storage System Technology and Industrial Development (the Guideline) issued by five ministries of China (Reform Commission, Ministry of Finance, Ministry of Science and Technology, Ministry of Industry and Information Technology, National Energy Administration) in October 2017 mentioned clearly one of the key commercialized technology should be 100MW VRB-ESS power station, there is several important large-scale flow battery projects promoted in China in 2018, such as 100MW/500MWh peak plant in Hubei, 200MW / 800MWh renewables integration in Liaoning, 200MW / 1,000MWh offshore wind integration in Jiangsu and renewable power integration in Qinghai. Some of the confirmed projects is listed in the following figure.

Figure 1. China’s vanadium flow battery energy storage projects development plan

Several provinces in south coastal area of China, such as Jiangsu, ESS is for peak shifting and arbitrage application as the urgent need of flexible/ Independent peak plants to support the summit power demand in summer. The 100MW/500MWh peak plant in Hubei is mostly to support power requirement of industrial parks. While Qinghai province is the most active place for renewable energy developing and requires large-scale ESS to support grid connection. VRB Energy has got involved closely in most of these projects, and looking forward to share experience and future prospects accordingly.

VRB Energy Operations (Beijing) Co. Ltd., used to known as Pu Neng, the supplier of the 2MW/8MWh VRB-ESS State Grid demonstration site in Zhangbei, Zhangjiakou, China, and 3MW/12MWh VRB-ESS in Zaoyang, Hubei, China. The 3MW/12MWh VRB-ESS in Zaoyang has commissioned in Oct 2018, and provided a technical foundation for the coming 100MW/500MWh project in Hubei. VRB Energy has followed up the 200MW / 1,000MWh offshore wind integration in Jiangsu and wind integration projects in Qinghai closely. Some of the projects are most likely to start construction in 2019.

Additionally, National Development and Reform Commission, state grid, and National Energy Committee issued the ESS price policy to support the ESS development in China. The policy includes increase the power price gap between peak time and off peak time, tax refund, and reward to the ESS project which can provide the good service to state grid, etc. With economic support and practical large-scale projects, the Chinese power market is expected to form a completed market mechanism in the near future.
Linked Donor-Acceptor Systems for Symmetric Nonaqueous Redox Flow Batteries
Authors: Rajewski Andrew , Mann Shane C. , Mortimer Nicholas J. , Dumitrascu Adina , Gillmore Jason G. , Guarr Thomas F.
Published: February 2020

A series of molecules containing electron donor and acceptor moieties were synthesized and analyzed for potential future use in redox flow batteries (RFBs). These compounds, including D-A, D-A-D, and A-D-A alkyl-linked systems, can exist in at least three stable oxidation states: an oxidized (catholyte) form, a reduced (anolyte) form, and the neutral species. For this study, donors included various organic heterocycles, while acceptors included several imides and diimides. In all cases, cyclic voltammetry revealed highly reversible electrochemical behavior for both the individual redox active moieties as well as for the fully linked system.

This approach provides for the independent optimization of anolyte and catholyte properties, while the covalent linkage results in a symmetric system whereby both RFB half-reactions generate an identical product (the neutral species). In principle, this may allow for elimination of the ubiquitous and expensive ion exchange membrane used in typical RFBs. Because the membrane can account for up to 40% of cell costs, this could represent an important opportunity to improve the economics of employing flow batteries for grid-level energy storage applications.

The synthesis, characterization and preliminary electrochemical investigation of these molecules will be described.

Figure 1
Strategies for Hydraulic Recharge of Zinc-Air Flow Batteries
Authors: Mahlendorf Falko , Fuchs David , Müller Christoph , Heinzel Angelika
Published: February 2020

The increased use of fluctuating renewable energy calls for efficient, safe and environmentally friendly energy storage solutions. To meet the variable power-, capacity- and profitability requests of mobile and stationary applications, it is necessary to identify promising materials. Zinc-air batteries with specific energy density higher than lithium-ion and low cost, highly available, eco-friendly active materials are suitable to fulfill these requirements. The use of a flow battery type with zinc-particles suspended in alkaline solution (zinc-slurry) in addition with high performance oxygen-reduction electrodes enables the development of high-power zinc-air batteries. This setup also allows the independent scaling of capacity and power. The recharging of this system can be performed due to classical electrical charging or due to a hydraulic recharge by changing the used zinc-slurry with a fresh one.

The cooperative project, ZnMobil, funded by the Federal Ministry of Economic Affairs and Energy in Germany combines the experience of industrial and academic partners (Covestro Deutschland AG; Grillo-Werke AG; VARTA Microbattery GmbH; Accurec Recycling GmbH; Technical University Freiberg, Gottfried Wilhelm Leibniz University Hannover; University of Duisburg-Essen; the fuel cell research center ZBT GmbH) to develop a zinc-air flow battery with high performance and economic efficiency.

Here we present strategies for the hydraulic recharging of zinc-air flow batteries. The battery system consists of a 100 cm² copper plate as current collector for the zinc-suspension electrode and an oxygen reduction electrode with a gas-diffusion layer (supplied by Covestro Deutschland AG). The zinc-slurry contains zinc particles (supplied by Grillo-Werke AG) suspended in alkaline solution (30 wt.-% KOH) and stabilized with polyacrylic acid.

Depth-of-discharge and battery resistance were measured for zinc-slurries in a flow system under regulated conditions. The influence of the depth-of-discharge and several additives on the rheology of the zinc-slurries was evaluated. Depending on the current density and additive selection, it is possible to achieve energies of up to 300 Wh during discharge.
(Invited) Advanced Redox Flow Battery Technologies
Authors: Wang Wei
Published: February 2020

Redox flow batteries (RFBs) have increasingly being recognized as a prominent candidate for large-scale energy storage due to their unique advantages of high safety, decoupling of power and energy, long lifespan, quick response, and potentially low cost. Electrolyte is de facto the most critical component in a RFB system. This presentation describes development of new electrolyte chemistries at Pacific Northwest National Laboratory. Salvation chemistry of the different electrolyte systems will be discussed, which provide a greater understanding of dynamic interactions between solvent-solvent, ion-solvent, and ion-ion at the molecular level. Such understanding is pivotal in developing new redox flow system with higher energy density and temperature stability. A new RFB based hydrogen generation technology will also be presented.
Scalable and Efficient Electrochemical Exfoliation of Graphite Felt As High-Performance Flow Battery Electrode
Authors: Zhu Hongli
Published: February 2020

Mass production of highly active graphite felt (GF) electrode is necessary to attain high power density and energy efficiency, which is essential to reduce the cost and enable the extensive industrial application. Herein, for the first time, we report a rapid and scalable electrochemical exfoliation of the GF in aqueous solution by breaking the weak van der Waals forces between the greaphitic layers through anion intercalation. The expansion of the graphite layers creates a distinctive layer by layer structure and introduces sufficient functional groups that intensifies the abundance of electrochemically active surface area resulting enhanced kinetics at the electrode-electrolyte interface and improved wettability enabling better electrolyte accessibility. Consequently, a rapid and reversible redox reactions with minimized overpotential and high volumetric capacity was achieved. In addition, the exfoliated GF (E-GF) electrode deliver voltage and energy efficiencies of 98.53 and 90.96 % at 40 mA cm-2 and 61.86 and 52.90 % at a high current density of 200 mA cm-2, individually. Compared to the traditional GF treatment method, by eliminating the high temperature and high energy consuming synthesis processes, our approach of electrochemical exfoliation is much faster and energy efficient. These results suggest the enormous potential of the exfoliated GF owing to its excellent electrochemical activity combined with its rapid, facile, and scalable nature.
Application of Nano-Dispersed Ionomer to Prolong Lifetime of Polymer Electrolyte Membrane Fuel Cells
Authors: Ahn Chi-Yeong , Kim Sungjun , Hwang Wonchan , Cho Yong-Hun , Sung Yung-Eun
Published: February 2020

In the late 1980s, the technique of impregnating ionomers (binders) into the electrodes of the fuel cells extended the proton transport pathway to the deep inside of the electrodes by forming lots of triple phase boundaries and also increased the durability by binding nano-sized catalysts physically. As a result of this technique, the amount of the catalyst used in the fuel cells is greatly reduced, and the performance can be greatly increased. In recent decades, catalysts for improving activity for oxygen reduction reaction (ORR) have been developed in several research groups. Although the activity of the catalysts has been remarkably improved, the catalysts do not exhibit such a high activity when it is applied to a practical fuel cells as membrane electrode assemblies (MEA) state. It has been argued that this is because the impregnated ionomer covers the surface of the catalyst and interferes with the mass transport of the gas (oxygen or etc.). Therefore, there is room for improvement in the performance of the MEA by improving the properties of conventional ionomers. In this study, we obtain an ionomer with improved properties by treating with a simple physical method, and apply it to practical fuel cells. As a result, we achieved high performance and durability, even though only the ionomer was replaced in MEA.
(Invited) Materials Design for Microbial Bioelectrochemical Devices
Authors: Minteer Shelley D.
Published: February 2020

Electrochemically interfacing bacteria with electrodes presents a dynamic new set of materials challenges. Bacteria naturally form biofilms on traditional electrode surfaces, but materials design can help promote extracellular electron transfer between the bacteria and the electrode within biofilms. This paper will discuss materials strategies for promoting biofilm formation, biofilm maintenance, and extracellular electron transfer within the film, as well as improving the lifetime of microbial bioelectrodes. We will discuss different strategies for biophotocurrent generation versus microbial fuel cells versus shock biosensors, including novel carbon materials, electrode treatments, redox polymers, and biopolymer engineering.
Nitrogen-Doped Carbon Catalysts Modified with Au-M (M = Co, Ni, Cu) Nanoparticles As the Anode Material for Direct Borohydride-Hydrogen Peroxide Fuel Cells
Authors: Balčiūnaitė Aldona , Vaičiūnienė Jūratė , Kruusenberg Ivar , Kaare Kätlin , Volperts Aleksandrs , Dobele Galina , Zurins Aivars , Tamašauskaitė-Tamašiūnaitė Loreta , Norkus Eugenijus
Published: February 2020

Direct borohydride-hydrogen peroxide fuel cells (DBHPFCs) have several advantages such as high theoretical cell voltage (2.11-3.02 V), high energy density (12-17 kWh kg-1) and, finally, no CO poisoning during their operation. Therefore, anode material is the key factor for complete direct oxidation of borohydride. This study is focused on the synthesis of the nitrogen-doped carbon (N-doped C) catalysts supported Au-M (M = Co, Ni, Cu) nanoparticles using a rapid microwave heating method with the aim to use them as the anode material for DBHPFC. The electrocatalytic activity of the prepared M/N-doped C and Au-M/N-doped C catalysts for the borohydride oxidation reaction (BOR) was evaluated using cyclic voltammetry and chronoamperometry. The direct borohydride-hydrogen peroxide fuel cell was assembled using Pt as the cathode and the prepared M/N-doped C and Au-M/N-doped C catalysts as the anodes. The performance of a DBHPFC operating with 1 M NaBH4 + 4 M NaOH as fuel and 5 M H2O2 + 1.5 M HCl as an oxidant was investigated at different temperatures.

It has been determined that the prepared Au-M/N-doped C catalysts have а higher activity and а better stability for the oxidation of borohydride compared to those of M/N-doped C (M = Co, Ni, Cu) catalysts. The direct borohydride-hydrogen peroxide fuel cell exhibited an open circuit voltage of cа. 1.8 V when the Au-M/N-doped C catalysts were assembled as the anodes.
Investigation of Hydrazine Electro-Oxidation on Zinc-Cobalt Coating Modified with Gold Nanoparticles
Authors: Šimkūnaitė Dijana , Zabielaitė Aušrinė , Balčiūnaitė Aldona , Vaičiūnienė Jūratė , Selskis Algirdas , Vaitkus Rimantas , Tamašauskaitė-Tamašiūnaitė Loreta , Norkus Eugenijus
Published: February 2020

In this study, the electro-oxidation of hydrazine in an alkaline medium was investigated on the zinc-cobalt (ZnCo) coating, which was deposited on the titanium (Ti) surface and then modified with low amounts of gold nanoparticles (AuNPs). The AuNPs-ZnCo/Ti catalysts with different amount of AuNPs were prepared via a facile electrochemical deposition technique followed by a simple and low-cost galvanic displacement. Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Analysis and Inductively Coupled Plasma Optical Emission Spectroscopy were used for the characterization of the surface morphology, structure and composition of the as-prepared AuNPs-ZnCo/Ti catalysts. Electrocatalytic behavior of catalysts was investigated towards the electro-oxidation of hydrazine in an alkaline medium using Cyclic Voltammetry.

It was found that the AuNPs-ZnCo/Ti catalysts were prepared with the Au loadings of 31, 63 and 306 µg cm-2 after the immersion of the ZnCo/Ti catalyts into the 1 mM HAuCl4 solution for 0.5, 1 and 5 min, respectively. Moreover, the ZnCo/Ti catalysts modified by AuNPs has significantly higher catalytic activity towards the electro-oxidation of hydrazine as compared to that of the ZnCo/Ti catalyst. Additionaly, modification of the ZnCo/Ti catalyst by AuNPs leads to the rather pronounced shift in hydrazine oxidation potential to more negative potential region and is followed by a substantial increase in direct hydrazine oxidation rate as compared to that of the unmodified ZnCo/Ti catalyst.
Fuel Cell Catalysts Encased in 1D and 3D Porous Frameworks
Authors: Farghaly Ahmed A. , Kariuki Nancy N. , Myers Deborah J.
Published: February 2020

The strong catalyst surface-ionomer interactions in the membrane electrode assembly (MEA) have a negative impact on the electrode performance in the polymer electrolyte fuel cells (PEFCs).1-4 A new series of encased platinum group metal catalysts have been designed in order to minimize the ionomer poisoning of the oxygen reduction reaction (ORR), local oxygen transport issues, and the lack of cathode performance durability. Nanoporous materials have a wide range of technological applications5-9 and are potential candidates to improve the performance of the PEFC catalysts. 1D and 3D ordered inorganic nanoporous structures with well-defined and uniform pores are used to host the catalyst nanoparticles and block the access of the ionomer aggregates to the catalyst surface. The rotating disk electrode (RDE) technique has been used to examine the effect of the host dimensionality on the ORR activity of the newly-designed PEFC catalysts. The effect of the host dimensionality on stability, durability and rate of the electrocatalyst dissolution have been evaluated by means of inductively coupled plasma mass spectrometry (ICP-MS).

References

Kongkanand and M. F. Mathias, J. Phys. Chem. Lett., 7, 1127 (2016).

Subbaraman, D. Strmcnik, A. P. Paulikas, V. R. Stamenkovic, and N. M. Markovic, Chemphyschem, 11, 2825 (2010).

Subbaraman, D. Strmcnik, V. Stamenkovic, and N. M. Markovic, J. Phys. Chem. C, 114 8414 (2010).

C. Cetinbas, R. K. Ahluwalia, N. N. Kariuki, and D.J. Myers, J. Electrochem. Soc.,
165(13), F1051 (2018).

A. Farghaly, R. K. Khan, and M. M. Collinson, ACS Appl. Mater. Interfaces, 10(25), 21103 (2018).

Demir, A. A. Farghaly, M. J. Decuir, M. M. Collinson, and R. B. Gupta, Mater. Chem. Phys., 216, 508 (2018).

Nahar, A. A. Farghaly, R. J. A. Esteves, and I. U. Arachchige, Chem. Mater., 29(18),7704 (2017).

A. Farghaly and M. M. Collinson, Langmuir, 32(23), 5925 (2016).

A. Farghaly, M. Lam, C. J. Freeman, B. Uppalapati, and M. M. Collinson, J. Electrochem. Soc., 163(4) H3083 (2016).

Acknowledgements

This work was supported by the United States Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office. Argonne is a U.S. Department of Energy Office of Science Laboratory operated under Contract No. DE-AC02-06CH11357 by UChicago Argonne, LLC.
Phosphoric Acid Loss Mechanism of High Temperature Proton Exchange Membranes
Authors: Lee Albert S , Choe Yoong-Kee , Matanovic Ivana , Kim Yu Seung
Published: February 2020

High temperature-polymer electrolyte fuel cells (HT-PEMFCs) traditionally utilize phosphoric acid-doped polybenzimidazole as proton exchange membrane.1 However, the retention of phosphoric acid within polymer matrix has been pointed out as one of the most critical factors that affect HT-PEMFC durability. Previously, we reported a new HT-PEMFC system in which a quaternary ammonium-functionalized polymer imparted a stronger ionic interaction which we deemed “ion-pair coordination” with phosphoric acid compared with that of polybenzimidazole,2 giving rise to improved water tolerance. In this study, we use a combination of 31P NMR and DFT computations to compare the ionic interactions between representative small molecule organic bases, benzimidazole or tetramethylammonium hydroxide, with phosphoric acid and water. Based of these results, we propose a new phosphoric acid loss mechanism in which the strongly interacting ion pairs can increase the phosphoric acid partition composition towards accommodating more phosphoric acid for better phosphoric acid retention.

References

Li, J.O. Jensen, R.F. Savinell, N.J. Bjerrum, Prog. Polym. Sci., 2009, 34, 449-477.

-S. Lee, J.S. Spendelow, Y.K. Choe, C. Fujimoto, Y. S. Kim, Nature Energy, 2016, 1, 16120-16124.
Advancement of Perfluorinated Alkaline Exchange Membrane Materials Toward Improved Durability
Authors: Strasser Derek , Neyerlin Ami , Meek Kelly M , Owczarczyk Zbyslaw R. , Antunes Christopher M , Pivovar Bryan S.
Published: February 2020

Perfluorinated (PF) alkaline exchange membranes have garnered attention due to the commercial success of the acidic analogue Nafion™, owing to it’s chemical stability, enhanced water mobility, and high performance in PEMFC systems. Furthermore, the incorporation non PGM catalyst materials available for AEMFC has the potential to significantly reduce cost. Current state-of-the-art PF AEM materials are derivatives of PF sulfonic acid ionomers wherein the sulfonic acid groups are modified to tether tetraalkylammonium cations. Previous research has indicated that a tether length of 6 carbon atoms from the sulfonamide linkage was sufficient to insulate the quaternary ammonium cation from the strong electron withdrawing PF backbone and was stable at 80°C for 2 weeks in 2M KOH indicating only ~10 % loss of IEC.1

Current research indicates that the most vulnerable functional group in the PF AEMs is the quaternary ammonium cation. Furthermore, there exists literature demonstrating small molecule imidazolium cations with enhanced base stability compared to tetraalkylammonium cations.2-4 The research presented will focus on furthering the base stability of PF AEMs through the incorporation of a sterically hindered imidazole ring. Presented is the synthesis of the 2-(2,6-dimethylphenyl)-1,4,5-trimethyl-imidazole (DMPTMIm) small molecule and its base stability, incorporation the DMPTMIm cation into PF materials, and membrane performance.

Park, A. M.; Owczarczyk, Z. R.; Garner, L. E.; Yang-Neyerlin, A. C.; Long, H.; Antunes, C. M.; Sturgeon, M. R.; Lindell, M. J.; Hamrock, S. J.; Yandrasits, M. A.; Pivovar, B. S., Synthesis and characterization of perfluorinated anion exchange membranes. ECS Trans.
2017,
80 (8, Polymer Electrolyte Fuel Cells 17 (PEFC 17)), 957-966.

Hugar, K. M.; Kostalik, H. A.; Coates, G. W., Imidazolium Cations with Exceptional Alkaline Stability: A Systematic Study of Structure-Stability Relationships. J. Am. Chem. Soc.
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3 (2), 160-165.

Sturgeon, M. R.; Long, H.; Park, A. M.; Pivovar, B. S., Advancements in anion exchange membrane cations. ECS Trans.
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69 (17, Polymer Electrolyte Fuel Cells 15), 377-383.
(Invited) Electronic Properties of ABO4 Photo-Catalysts Under Nb-Substitution and Phase/Pressure-Related Distortions
Authors: Huda Muhammad N , Bainglass Edan , Sarker Hori Pada , Rao Pratap
Published: February 2020

Both SbTaO4 and SbNbO4 in the orthorhombic α-Sb2O4 phase have demonstrated pure water splitting as photo-catalysts. Previous experimental studies have shown a significant difference in reported bandgap values for SbTaO4 such as 3.71 eV and 2.28 eV. We have studied SbTa1-xNbxO4 (x = 0, 0.25, 0.5, 0.75, 1) in the tetragonal, orthorhombic, and monoclinic phases. The resulting Sb3+
M
5+O-2
4 material can be classified as a ns2
md0 ternary metal oxide. We have studied the effects of structural symmetry related distortions on the band gaps and overall energetics of SbMO4 compounds (M = Ta, Nb). Evolution of the electronic structures was studied as one transitions from a system of 4d bands to 5d bands, and whether this has any effect on the Sb oxidation state or its lone pair s electrons. From the atomic point of view, electronic correlation energy is higher in Ta 5d than in Nb 4d, and Nb 4d band is higher in energy than Ta 5d. These were examined in terms of oxidation states in their respective solids. We look at the effects of increasing Nb concentration on the electronic structure of SbTa1-xNbxO4 alloy with emphasis on polyhedral and overall cell distortions. We decouple the effects caused by the presence of different nd cations from those caused by distortions and reorientation of various polyhedra. BiVO4 Belongs to the same group of materials; we will also present the electronic structure changes caused by Nb incorporation in BiVO4 and the application of external pressure. Through the analyses of the chemical-potential landscape, we have determined the single-phase stability zone of BiVO4 with the Nb doping. Application of external pressure improved the single-phase stability zone. We have also focused on the local structural distortions near the Nb doping site, especially on the BiO8 octahedra. We have shown here that pressure-induced symmetrization of BiO8 dodecahedron could lower the electron’s effective mass and therefore can help to improve the photo-conduction property of BiVO4.

This work is supported by NSF-award # 1609811. We also acknowledge the computational time from Texas Advanced Computing Center (TACC).
Hydrogenation of Carbonyl Compounds over Pd in Aqueous Phase Under Charged Conditions: Role of Organic Molecular Structure
Authors: Meyer Laura C , Sanyal Udishnu , Camaioni Donald M , Stoerzinger Kelsey A , Gutiérrez Tinoco Oliver Y , Lercher Johannes A
Published: February 2020

Electrocatalytic hydrogenation (ECH) is a promising approach for energy conversion utilizing renewable electricity to transform biogenic carbon sources to more useful feedstocks. Carbonyl groups are one of the most abundant and highly reactive functionalities of bio-derived molecules. Recent studies of benzaldehyde ECH showed a higher activity of C-supported Pd compared to other metals, i.e., Pt, Rh, Ni.

In the present study we explore this catalytic chemistry further, comparing the reduction of aromatic and aliphatic carbonyl compounds on Pd/C with the aim to understand the influence of molecular structure on the reaction pathways and selectivity in ECH. The experiments were conducted over the potential range of -0.1 VRHE to -0.3 VRHE at low temperatures and atmospheric pressure. The aromatic carbonyl compounds benzaldehyde, acetophenone, and furfural showed significant reactivity toward hydrogenation, whereas the aliphatic carbonyl compounds butyraldehyde and cyclohexanone exhibited small or negligible reduction rates. Under these conditions, the reactive carbonyls all reduced to alcohols without secondary products. The Figure demonstrates the result of the cathodic potential on the reduction of carbonyls. The H2 evolution reaction (HER) was the prevalent side reaction during ECH and increased exponentially with negative potential. Benzaldehyde reduction rates were highest and increase linearly, followed by acetophenone reduction rates, which plateaued at -0.2 VRHE. Furfural reduction rates increased exponentially with cathodic potential albeit with lower values than benzaldehyde and acetophenone. Rotating disk electrode (RDE) experiments showed that the presence of organic compounds affects charge transfer processes to an extent that is a function of the molecular structure. These results indicate a competitive adsorption of organic compounds and hydrogen on Pd and highlight the dependence of hydrogenation rates, HER rates and charge transfer on the molecular structure, which determines the adsorption strength of the organic molecules. TCH rates are plotted against their OCV values in the Figure, showing lower rates than ECH. This allows to conclude that an electrochemical mechanism is dominating the reaction under cathodic bias. The data agrees well with a kinetic model, where the first hydrogen addition (through a proton coupled electron transfer) is the rate determining step.

This work helps to understand the influence of molecular structure on the rates of electrocatalytic hydrogenation of organic compounds and simultaneous H2 evolution. Our studies will enable predictive models - based on common principles in catalysis - to be applied to other metals and organic compounds.

Figure 1
(Keynote) Generation of Hot Electrons in Plasmonic and Hybrid Metastructures for Photochemical Applications
Authors: Govorov Alexander O. , Besteiro Lucas V. , Chang Le , Wang Zhiming
Published: February 2020

Generation of energetic (hot) electrons is an intrinsic property of any plasmonic nanostructure under illumination. Simultaneously, a striking advantage of metal nanocrystals over semiconductors lies in their very large absorption cross sections. Therefore, metal nanostructures with strong and tailored plasmonic resonances are very attractive for photocatalytic applications in which excited electrons play an important role [1,2]. However, the central questions in the problem of plasmonic hot electrons are the number of optically excited energetic electrons in a nanocrystal and how to extract such electrons. Here we develop a theory describing the generation rates and the energy distributions of hot electrons in nanocrystals with various geometries [3-5]. In particular, we show that nanostructures with strong and extended plasmonic hot spots generate unusually large numbers of energetic electrons, which can be observed using ultra-fast transient spectroscopy [4,6] as well as photochemistry. Hot-electron generation together with non-radiative plasmonic transfer [7] represent efficient methods to convert optical energy into other forms, such as electricity or chemical energy.

V. Hartland, L. Besteiro, P. Johns, A. O. Govorov, What’s so Hot about Electrons in Metal Nanoparticles? (perspective paper), ACS Energy Letters, 2, 1641–1653 (2017).

Sousa-Castillo, M. Comesaña-Hermo, B. Rodríguez-González, M. Pérez-Lorenzo, Z. Wang, X.-T. Kong, A. O. Govorov, and M. A. Correa-Duarte, J. Phys. Chem. C, 120, 11690–11699 (2016).

O. Govorov, H. Zhang, V. Demir, and Y. K. Gun’ko, Nano Today, 9, 85 (2014).

Harutyunyan, A. B. F. Martinson, D. Rosenmann, L.K. Khorashad, L.V.Besteiro, A.O.Govorov, and G.P. Wiederrecht, Nature Nanotechnology 10, 770–774 (2015).

V. Besteiro, X.-T. Kong, Z. Wang, G. V. Hartland, A.O. Govorov, ACS Photonics, DOI: 10.1021/acsphotonics.7b00751 (2017).

E. Sykes, J. W. Stewart, G. M. Akselrod, X.-T. Kong, Z. Wang, D. J. Gosztola, A.B.F. Martinson, D. Rosenmann, M. H. Mikkelsen, A. O. Govorov, G. P. Wiederrecht, Nature Communications, 8, 986 (2017).

-M. Roller, L.V. Besteiro, C. Pupp, L. Khosravi Khorashad, A. O. Govorov, T.Liedl, Nature Physics, 13, 761-765 (2017).
(Invited) Rational Design of Hybrid Photoelectrode Assemblies for Solar Fuel Generation
Authors: Janáky Csaba
Published: February 2020

Given that CO2 is a greenhouse gas, using the energy of sunlight to convert CO2 to fuels (such as methanol or methane) or basic chemicals represents a value-added approach to the simultaneous generation of alternative fuels and environmental remediation of carbon emissions. Electrochemistry and photoelectrochemistry have been proven to be a useful avenue for solar water splitting. CO2 reduction, however, is multi-electron in nature (e.g., 6 e- to methanol) with considerable kinetic barriers to electron transfer. It therefore requires the use of carefully designed electrode surfaces to accelerate e- transfer rates to levels that make practical sense. In this talk I will present some collaborative work, carried out together with Prof. Rajeshwar, on hybrid photoelectrodes leading to enhanced efficiency, selectivity, and stability.

First, I will present the use of electrosynthetic (and photoelectrosynthetic) methods for preparing semiconductors on nanocarbon-modified electrode surfaces. Composites of nanocarbons with both inorganic and organic semiconductors represent an interesting class of new functional materials. Therefore, I will show how electrodeposition can be used to tune composition, crystal structure, and morphology of the nanocomposites for targeted applications.

In the second part of my talk, I will focus on how to use semiconductor/nanocarbon hybrid materials for the photoelectrochemical reduction of CO2. Carbon nanotubes and graphene (either alone, or as building blocks of organized 3-D superstructures) can facilitate enhanced charge transport property for the photoelectrodes. I will present examples for Cu2O, TiO2, and Fe2O3-based electrodes, where the nanocarbon-containing photoelectrodes outperformed the pure semiconductor counterparts, both in terms of the achieved current densities and stability. Taking these observations together, as a general model will be presented on the role of the nanocarbon scaffold.
Surface Structural Evolution of Pd Nanosheets during Aging and Their Effect on (Electro-)Catalytic Activities
Authors: Zhang Yu , Xia Younan , Shao Minhua
Published: February 2020

Advances in probing the correlations between surface atomic structures of noble metal nanocrystals and their catalytic activities are vital for the development of effective catalysts. In general, the nanocrystals with well-preserved morphology over time is believed to present stable and consistent physicochemical properties. However, little attention has been paid to their surface structural evolution during aging, which might significantly alter their catalytic activities. In this work, hexagonal Pd nanosheets with an average thickness of ca. 0.93 nm (around four atomic layers) were synthesized and studied before and after aging as stable colloidal suspension at room temperature. Upon exposure to the electron beam (e-beam) of high-magnification transmission electron microscopy (TEM, > 150k, 200 kV), the fresh Pd nanosheets with (111) facet dominated on the surface immediately developed into poriferous and quasi-polycrystalline nanosheets. However, the Pd nanosheets became much more stable under e-beam after aging in water/ethanol at room temperature for two months. In addition, diverse defects were observed on the surface of the aged Pd nanosheets, including dislocations, lattice distortions, twin boundaries and vacancies, indicating the atomic reconstruction during aging. The driving force of structural transformation was found to originate from the gradual removal of surfactants and thus induced localized strain during aging, as evidenced by the greatly improved electrochemical active surface areas (ECSA) after aging. Electrochemical evaluation further demonstrated that the fresh Pd nanosheets possessed high activities for ethanol oxidation, formic acid oxidation and the reduction of 4-nitrophonel. The results suggest that the surface structural evolution during aging, which tends to be ignored, has a critical effect on catalytic properties. Our studies might provide insight on the design and processing of advanced nano-catalysts.
Hydrogen PEC Supernode: Emergent Degradation Mechanisms with Integration and Scale up of PEC Devices
Authors: Young James L. , Deutsch Todd G , Danilovic Nemanja
Published: February 2020

This talk will give an overview of the HydroGEN Photoelectrochemistry (PEC) Supernode and present recent progress. This Supernode project is collaboration of nine PEC capability nodes that are part of the HydroGEN Advanced Water Splitting Materials consortium. These nodes are contributing to a common objective of developing understanding of integration issues and emergent degradation mechanisms of PEC devices beyond the current research scales that typically does not exceed 1 cm2 active areas. Larger devices are expected to introduce new component integration challenges and pathways for degradation that this PEC Supernode project will identify and propose pathways for future progress.

The PEC Supernode project tasks include: 1) Photoreactor chassis fabrication and baselining, 2) development, fabrication, and testing of larger area PEC devices, 3) development of in-situ morphology and corrosion analysis techniques and characterization, and 4) analysis of durability mechanisms and impacts using modeling LCA and TEA. A new photoreactor chassis will be presented that has been designed to facilitate indoor and on-sun efficiency and durability benchmarking measurements. The design will be validated in a preliminary set of multi-institution round robin measurements toward understanding and harmonizing measurement conditions and protocol. This preliminary protocol and initial set of round robin results will be presented.