bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Electrolyte Composition on the Performance of Coal Char-Derived Carbon Supercapacitors
Authors: Karimi Zahra , Moon Jaron V , Ginkel Chanel Van , U1302137 Douglas , Malzahn Joshua , Eddings Eric , Warren Roseanne
Published: July 2021

Research regarding supercapacitors has vastly grown over the past decade. The advantages of supercapacitors include high power density, rapid charge/discharge capability, and a long cycle life. Current applications of supercapacitors are limited by the need to develop new, low-cost electrode materials for electric double layer capacitors and pseudocapacitors [1]. Coal char is the solid product of a low-temperature coal carbonization process, and is currently used primarily as an ultra-low-cost fuel for electric power generation. As such, coal char consists mainly of hard carbons and ash [2]. Upon ash removal, the hard carbons in coal char may serve as a promising, low-cost, supercapacitor electrode material. This research will present the use of inexpensive coal char as an electrode material for supercapacitors, with particular focus on the effects of various electrolyte compositions on the performance of coal-derived carbon supercapacitors.

Electrolyte composition plays a large role in the electrochemical properties of a supercapacitor, affecting: ion interactions with electrode surface functional groups; electric double layer capacitance; thermal stability; and allowable voltage range. In this work, bituminous grade coal char from a Utah mine is pulverized, pyrolyzed, and washed in a base solution followed by an acid solution to remove residual ash. SEM imaging and BET surface area measurements are used to characterize the coal. The purified coal char is mixed into a slurry of coal char, Super P binder, and dimethylformamide, then applied on a stainless-steel plate to create supercapacitor electrodes. Three-electrode open-cell electrochemical measurements are used to characterize the supercapacitor performance of the coal char in varying electrolyte solutions using a Gamry Interface 1000E potentiostat. The different electrolytes explored include: aqueous acid 0.5 M H2SO4, aqueous base 6 M KOH, and aqueous neutral solutions 0.5 M Na2SO4, 4 M LiNO3, water-in-salt electrolyte using 12.5 M NaClO4, . Voltage range, specific capacitance, electrochemical impedance, and charge-discharge characteristics of the coal char in the different electrolytes are characterized by cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy measurements. The results provide important insight into the optimal electrolyte composition for use with coal char supercapacitor electrodes, and contribute to current understanding of electrode-electrolyte interactions in carbon supercapacitors.

This work is supported in-part by NSF Award #1742696.

Reference

1.Rakesh Kumar Gupta, Mukul Dubey, Parashu Kharel, Zhengrong Gu, Qi Hua Fan, Biochar activated by oxygen plasma for supercapacitors, Journal of Power Sources, Volume 274, 2015, Pages 1300-1305.

2. H. H. Schobert, Coal; The Energy Source of the Past and Future, pg. 9, American Chemical Society, Washington (1987).

Figure 1
The Green Electrochemical Synthesis of Periodates and Application in API Synthesis
Authors: Waldvogel Siegfried R , Arndt Sebastian
Published: July 2021

Periodates represent one of the most powerful and versatile oxidizers for organic synthesis. Common ways to generate it electrochemically employ lead dioxide anodes. The disintegration of these electrodes cause contaminations which impede sensitive applications.[1] The purification of periodates makes this reagent usually too costly pharmaceutical applications. With the use of boron-doped diamond a direct conversion of the inexpensive sodium and potassium iodide within an eight-electron oxidation process renders periodate. The novel process is scalable, heavy metal-free and can be conducted in batch as well as flow electrolyzers.[2] This approach can also be used for the regeneration of periodates from iodates. The process was implemented in a new synthetic approach to levetiracetam, which demonstrates the technical application and recycling of iodates in API synthesis.[3] The reactor concepts for the efficient preparation of multi-kg quantities will be presented.

References:

[1] D. Pollok, S. R. Waldvogel, Chem. Sci. 11 (2020) 12375–12592.

[2] S. Arndt, D. Weis, K. Donsbach, S. R. Waldvogel, Angew. Chem. Int. Ed.
132
,
(2020) 8112-8118.

[3] S. Arndt, B. Grill, H. Schwab, G. Steinkellner, U. Pogorevčnik, D. Weis, A. M. Nauth, T. Opatz, K. Donsbach, S. R. Waldvogel, M. Winkler, Green Chem.
(
2020), accepted.
(Invited) Energy Conversion and Storage:Novel Materials and Operando Methods
Authors: Abruna Hector
Published: July 2021

This presentation will deal with the development of new materials and operando methods for energy conversion and storage with emphasis on fuel cells and battery materials and technologies. The presentation will begin with a brief overview of the methods employed. Particular emphasis will be placed on the use of X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) X-ray microscopy and tomography and transmission electron microscopy (TEM) under active potential control. The utility of these methods will be illustrated by selected examples including electrocatalysts for the oxygen reduction reaction (ORR) in acid and base, hydrogen oxidation reaction (HOR) and spectroscopic studies of Li/S and Li/Se batteries and Li metal deposition and dendritic growth. The presentation will conclude with an assessment of future directions.
(Invited) Single Nanosheet Photoelectrochemistry: Probing Charge Recombination and Transport Pathways in Monolayer Transition Metal Dichalcogenide Photoelectrodes
Authors: Sambur Justin , Wang Li , Van Erdewyk Michael
Published: July 2021

Monolayer heterojunctions such as MoS2/WS2 are attractive for solar energy conversion applications because the interfacial electric field spatially separates charge carriers in less than 100 femtoseconds. Photoelectrochemical cells represent an intriguing platform to collect the spatially separated carriers. However, the recombination, transport, and interfacial charge transfer processes that take place following the ultrafast charge separation step have not been investigated. Here we demonstrate novel charge recombination and transport pathways in monolayer MoS2/WS2 photoelectrochemical cells by spatially resolving the net collection of carriers (i.e., the photocurrent) at the single nanosheet-level. We discovered an excitation wavelength-dependent recombination pathway that depends on the heterojunction stacking configuration and the carrier generation profile in the heterostructure. Photocurrent mapping measurements revealed that charge transport occurs parallel to the layers over micrometre-scale distances even though the indium tin oxide electrode and liquid electrolyte provide efficient charge extraction pathways via intimate electron- and hole-selective contacts. Our results reveal how composition heterogeneity influences the performance of bulk heterojunction electrodes made from randomly oriented nanosheets and provide critical insight into the design of efficient heterojunction photoelectrodes for solar energy conversion applications.

Figure 1
Thermal-Electro-Chemical Modeling of Capacity Degradation in Li-Ion Cell
Authors: Sahu Swati , Buddhiraju Venkata Sudheendra , Runkana Venkataramana
Published: July 2021

Active material dissolution as well as Solid Electrolyte Interface (SEI) film growth are the major factors contributing towards capacity degradation in Li-ion cell. The effect of these factors on capacity fade is exacerbated at high temperature. We propose a thermal-electro-chemical model for studying the effect of both active material dissolution and SEI film growth in a Spinel LiMn2O4/Graphite Li-ion cells. While Mn disproportion reaction has usually been considered as the mechanism of active material loss for modeling purposes, recent studies suggest that the acid attack on Manganese spinel due to electrolyte decomposition causes the dissolution of Mn into the electrolyte. The exact mechanism of Mn dissolution is, however, unknown. In this study we model both mechanisms separately and compare the modeling results. The model is aimed to investigate capacity degradation at different ambient temperature- 25oC, 45oC and 60oC and at different current densities- 0.1C, 1C and 3C. The thermal model is included to study change in temperature due to reversible, irreversible and ohmic heat generation and its subsequent effect on material properties. The results include discharge profiles, film resistance due to SEI film growth, volume changes in electrode and state-of charge of anode.
Modelling Diffusion at Random Arrays of Active Sites: Revisiting the Voronoi Tessellation Concept
Authors: Pireddu Giovanni , Svir Irina , Amatore Christian , Oleinick Alexander
Published: July 2021

Many practical systems at micro- and nanoscale can be represented as arrays of active sites distributed randomly [1]. As shown previously these systems can be efficiently addressed theoretically by using Voronoi diagrams [2, 3] which allows facile tessellation of the system into the unit cells around each active sites. The overall current flowing in the system can then be evaluated by modelling diffusion-reaction processes inside every unit cell and summing the contributions from individual active sites. Although this approach is tempting by its simplicity and efficiency [3] one should bear in mind that Voronoi diagram representing the unit cells by polygonal prisms remains approximation and as each approximation remains valid only under certain conditions. In this work [4] we show that even for the case of diffusion limited electron transfer (ET) the actual shapes of the unit cells are more complicated and depend on the local configuration of the neighbouring active sites. This was exemplified on the small patches of the random arrays with band-like and disk-like active sites via simulations and in the case of band-like active sites confirmed by analytical derivations.

Importantly, by comparing the total array current obtained by employing Voronoi tessellation and simulation of the system without any approximations we found that they agree well (relative error ca. 5% or less). At the same time, the individual contributions from the active sites are reproduced with a much larger relative error [4]. The latter suggests that in the case of kinetic control or reaction mechanisms that are more complicated than simple ET the diffusion-reaction competition between the active sites may become even stronger eventually leading to significant deviations from the total current predicted on the basis of the Voronoi approximation. This is currently investigated in our team.

Fig. 1. Comparison between the Voronoi tessellation boundaries (white dashed lines) and the actual boundaries (coloured surface) of the unit cells. Three disk-type active sites are shown as white disks.

References

[1] O. Sliusarenko, A. Oleinick, I. Svir, C. Amatore. J. Electrochem. Soc. 167, 2020, 013530.

[2] T. J. Davies and R. G. Compton. J. Electroanal. Chem. 585, 2005, 63.

[3] O. Sliusarenko, A. Oleinick, I. Svir, C. Amatore. ChemElectroChem 2, 2015, 1279.

[4] G. Pireddu, I. Svir, A. Oleinick, C. Amatore, Electrochim. Acta 365, 2020, 137338.

Figure 1
Solid-Solution Photocatalysts: New Insights Via Percolation Theory
Authors: O'Donnell Shaun , Maggard Paul
Published: July 2021

Solid-solution semiconductors in many metal-oxynitride and metal-chalcogenide systems have been demonstrated to efficiently drive water oxidation and/or reduction under visible-light irradiation as suspended powders or thin films, respectively. This occurs despite the high level of inherent atomic-level disorder that would normally be expected to decrease charge mobility and increase charge recombination in these systems. Within the mixed-metal oxides, current results will be presented on the syntheses, structures and photoelectrochemical properties of the solid solutions Cu5(Ta1-x
Nb
x
)11O30 and (Ba1-x
Sn
x
)(Zr1-yTi
y
)O3 with band gaps that span the visible light energies from ~1.9 to 3.1 eV. Their band gaps, band edge energies and photocatalytic activities for the production of molecular hydrogen and molecular oxygen are found to be a sensitive function of their Ta-to-Nb or Zr-to-Ti and Ba-to-Sn molar ratios, as shown in the Figure for the (Ba1-x
Sn
x
)(Zr1-yTi
y
)O3 solid-solution semiconductor. Notably, electronic structure calculations reveal that the highest photocatalytic activities should occur at the percolation thresholds of the mixed transition-metal frameworks, wherein extended diffusion pathways for the minority carriers start to form across the surfaces. In the semiconductors that will be described, the extended diffusion pathways constitute the lowest energies of the conduction bands and/or highest energies of the valence bands, and thus revealing an underlying driving force for achieving efficient charge separation in solid-solution systems.

Figure 1
A Reusable Rgo/BiVO4 Photocatalyst for Hydrogen Peroxide Synthesis in Different Flow Systems
Authors: Dhabarde Nikhil , Carrillo-Ceja Orlando , Subramanian Vaidyanathan
Published: July 2021

The photocatalytic H2O2 production is a sustainable and eco-friendly process, requiring mostly water, oxygen, and sunlight. In previous study, bismuth vanadate (BiVO4), a semiconductor with a low band gap energy (~2.4 eV) was encapsulated with reduced graphene oxide (rGO) to promote the separation and transport of charges, preventing the recombination of photogenerated electron-hole pairs in BiVO4. 1% GO loading on BiVO4 was found to deliver effective H2O2 synthesis. H2O2 shows stability in acidic pH (~3), hence the effectiveness of the rGO/BiVO4 was tested under different types of acids. The order of efficiency of the acids is as follows: oxalic acid > phosphoric acid > formic acid > perchloric acid. This study involves the stability and reusability aspects of rGO/BiVO4 exhibiting significant H2O2 synthesis in the presence of oxalic acid catalyzing two-electron O2 reduction reaction. The photocatalytic H2O2 synthesis reaction following a zero-order kinetics, while the photocatalytic H2O2 decomposition following a first-order kinetics has been proposed as a mechanistic insight. A photocatalytic flow reactor study has also been evaluated to assess the feasibility of H2O2 generation in different reactor systems. Photocatalytic performance of rGO/BiVO4 composite was analysed in batch as well as flow reactor conditions.
Development of Electrolysis Process and Designing the Instrument with Energy Source of Solar Cell Module for the Production of Alkaline and Acidic Waters
Authors: Kurniawan Ekki
Published: July 2021

Electrolysis is a process of decomposing a substance or solution using an electric current. Electrolysis of pure water will create hydrogen gas on the cathode side and oxygen gas on the anode side. Mineral water electrolysis can produce alkaline water and acidic water, which is beneficial for improving public health. Alkaline water can use to drink-health, while acidic water can serve as an external medicine. The maximum pH standard for drinking water set by WHO (2006) and the Indonesian Ministry of Health (2010) are 9.5 and 8.5. Currently, the equipment for producing alkaline water and continuous acidic water is available on the market; however, has a weakness, which is that it is still quite expensive and not yet affordable to the general public. There is a batch type mineral water electrolysis device which is relatively inexpensive, but there are still many shortcomings, including a long reaction rate, large electrical energy. The composition of the water content of the production results from continuous and batch types has not been tested analytically both in quality and quantity, besides that the theory underlying the process has not been explained in the literature. This research intends to develop and modify a batch-type water electrolysis process with the energy source of the electrolysis instrument coming from the sun through the solar cell module stored in the battery; the voltage can be increased and regulated by a power electronic converter. The electrolysis instrument is designed to facilitate the formation or efficient production of acidic and alkaline water, so in such a way that not much hydrogen gas at the cathode side and oxygen gas at the anode side were generated simultantly. The results of the mineral water electrolysis experiment at an average voltage of 46 volts and an average volume of 1400 mL for one hour required an average current of 61 mA, the average current efficiency for alkaline and acid water formation of 3.35%, and 9.47 %, the average pH values for acids and bases are 3.8 and 9.0, the amount of water that becomes hydrogen and oxygen gas is only 0.021mL or about 0. 0015%. The test results on PDAM water in Cibenying Kaler, Bandung city of Indonesia, showed that the number of mineral ions Ca2+, Mg2+, Cl-, NO3
- , and SO4
2-before electrolysis were respectively: 24.03; 7.92; 23.8; 51.69; and 3.69 mg/L, after electrolysis at the anode side were respectively: 7.07; 5.15; 110; 97.39; and 10.39 mg/L, at the cathode side were: 25.75; 9,54; 10.7; 31.04; and 0.65 mg/L. These values indicate that the alkaline water content on the cathode side meets potable standards. The final result of this research is that a portable mineral water electrolysis instrument has been made, not only using solar energy sources but also using AC voltage from national electricity company so that it can be easily used by the community.
Nanoscale Electrochemistry Study Using SECCM Option of Park Systems
Authors: Zhang Jiali , Kim Byong
Published: July 2021

Scanning electrochemical cell microscopy (SECCM) is a nanoelectrochemical scanning probe technique that creates a confined electrochemical cell (droplet) via meniscus contacting the surface by employing an electrolyte filled micropipette containing quasi-reference counter electrode(QRCE).[1] It is particularly useful to investigate the heterogeneity, or local electrochemical properties of the electrode surfaces by direct mapping the electroactivity with nanoscale resolution.

In this study, the electrochemically reversible [Ru (NH3)6]3+/2+ electron transfer process at a highly ordered pyrolytic graphite (HOPG) surface was recorded using Park NX12 AFM system. A single barrel glass nanopipette with Ag/AgCl inserted as QRCE was utilized. Using previous successful experience in commercializing pipette-based electrochemical microscopy,[2] Park Systems’ hardware and software enables localized nanoscopic cyclic voltammetry measurements conducted at each pixel each time the meniscus contacts the surface. Thus, a spatially resolved surface electroactivity mapping of HOPG at various scan rates were created with high-throughput at the micro-/nanoscale. The difference in electrochemical activity measured at the edge plane relative to the basal plane surface was shown.

This work demonstrates that Park Systems’ commercial SECCM option is promising for quantitative electroanalysis at the nanoscale, with potential applications in energy storage (battery) studies and corrosion research.

[1] Gao, R., Edwards, M. A., Qiu, Y., Barman, K., & White, H. S. (2020). Visualization of Hydrogen Evolution at Individual Platinum Nanoparticles at a Buried Interface. Journal of the American Chemical Society.

[2] Shi, W., Goo, D., Jung, G., Pascual, G., Kim, B., & Lee, K. Simultaneous Topographical and Electrochemical Mapping using Scanning Ion Conductance Microscopy–Scanning Electrochemical Microscopy (SICM-SECM).

Figure 1
Noble-Metal-Free Ni-N-C Catalyst for Efficient Electrochemical Synthesis of Hydrogen Peroxide from Oxygen Reduction Reaction Under Both Acidic and Alkaline Conditions
Authors: Shahcheraghi Ladan , Zhang Chunyang , Lee Hye-Jin , Cusack-Striepe Melissa , Higgins Drew C.
Published: July 2021

H2O2 is a valuable, environmentally friendly oxidizing agent with a wide range of applications from the provision of clean water to the synthesis of valuable chemicals. The on-site electrocatalytic production of H2O2 would bring the chemical to uses beyond its present reach. The successful commercialization of electrochemical synthesis of H2O2 through 2e- oxygen reduction reaction (ORR) and the efficiency of the process depends greatly on the availability of cost-effective catalysts with high selectivity, activity, and stability. Among the catalysts, heat-treated metal-nitrogen-carbon materials (M-N-C) are noble-metal-free alternatives to the expensive state-of-the art platinum-based catalysts and have attracted massive attention due to their low-cost, high abundance, and efficient catalytic performance towards ORR. Herein, we report the synthesis and electrocatalytic assessment of a M-N-C catalyst for the synthesis of H2O2 through ORR in both acidic and alkaline media. The catalyst was based on nickel, and prepared by pyrolyzing a mixture of nickel (II) chloride and nitrogen/carbon precursors. This talk will focus on the impact of nickel content on the performance, with catalyst characterization correlated with electrochemical results to gain insight into electrochemical activity and selectivity towards H2O2.
Enhanced Catalyst Stability Via Chemically Grafted Polyaniline Groups for PEMFC
Authors: Chenzhao Li , Zhu Limin , Gong Qing , Song Liang , Sun Chengjun , Liu Yuzi , Xie Jian
Published: July 2021

The promising performance from the platinum group metal (PGM) catalysts make them the most practical catalysts for the commercialization of the polymer membrane fuel cells (PEMFCs). However, the excellent initial performance is not good enough for massive applications, particular for the fuel cell vehicles, which requires the long-term durability. Both the performance and the durability of catalysts strongly impact the applications in a wide range of operations of fuel cells, from stationary power generation to the transportation power propulsion. Catalyst stability plays a very important role on reducing the operation cost and increasing the lifetime of PEMFCs. Herein, a concept is proposed, which enhances the lifetime of PEMFCs through engineering the surface of catalyst supports. By covalently grafting NH2 groups on carbon (NGCB) surface, followed by polymerizing polyaniline (PANI) onsite on NFCB surface (using introduced NH2 groups as precursor), Pt L-edge goes to higher energy level, suggested by XAS measurement. Such modification can increase the barrier for Pt’s oxidation. In this study, carbon supports with different PANI loadings were synthesized and the Pt nanoparticles were loaded onto these supports. The synthesized catalysts were characterized for their morphology and structure using TEM, XRD, BET and Hg porosimetry. Both RDE and MEA tests were carried out for these catalysts for their fuel cell performance. The results show that the energy levels of Pt L-edge were increased with PANI loading. Besides, the membrane electrode assembly (MEA) testing results prove that the catalyst stability was improved with PANI loading in certain range. Three different PANI loadings were analyzed: 0.2, 0.25 and 0.33 in mass fraction of NFCB. MEAs results show that the beginning of life (BOL) performances of three catalysts were almost same. But when it comes to the catalyst stability test, the performance losses between BOL and EOL at 0.8 A·cm-2 in air are 120 mV, 90 mV and 45 mV for the three catalysts, respectively, after 30k square wave cycling using the standard testing protocol from the Department of Energy (DOE).
Enabling Real-Time Quantification of Electrochemical Desorptionphenomena with Sub-Monolayer Sensitivity
Authors: Cavalca Filippo , Scott Søren
Published: July 2021

Across many scientific and industrial fields, it is a challenge to analyze chemical reaction products with high sensitivity and fast time-response. This is especially true in systems related to electrochemical energy conversion and storage, such as batteries and fuel cells, where accurate monitoring of fast and transient reaction phenomena often reveals key insights.

Here, we present a unique analysis instrument using a microchip-based inlet system to couple a mass spectrometer directly to any liquid test environment, aqueous or non-aqueous, and exhibits a sensitivity up to 2-3 orders of magnitude than conventional differential electrochemical mass spectrometry (DEMS).(1–3) The instrument allows to measure the evolution of volatile products and consumption of reactants at electrode surfaces. Due to its extraordinary sensitivity, the system can measure all the individual volatile molecules desorbing from an electrode surface during a single electrochemical turnover. Product formation can be measured from total Faradaic currents of 1 mA all the way down to 200 nA, corresponding to approximately 0.2% of a monolayer (ML) desorbing from the electrode surface in 1s. These features enable time-resolved, fully quantitative measurements of transient phenomena during electrochemistry, providing fundamental insight in the electrochemical reaction mechanisms. Furthermore, an accurately calibrated on-chip gas system allows rapid gas switching between different gases, both inert and reactive. Due to the near-instantaneous equilibration between gas and electrolyte, the transient response of electrodes to rapid gas exposure changes can be measured.

As direct evidence of the ultrahigh sensitivity, i
n situ quantification the anodic desorption of less than ~1% of a ML of hydrogen on a Cu electrode in alkaline electrolyte (Fig. 1) is shown.(4) Finally, several examples of quantitative electrochemical measurements will be presented, including lattice oxygen contribution during OER on NiFeOxHy,(2) and hydrocarbon oxidation of propene on palladium. (3, 5)

Fig.1 H2 desorption on Cu(pc) in 0.1 M KOH.
(4)

D. B. Trimarco et al., Electrochim. Acta. 268, 520–530 (2018).

C. Roy et al., Nat. Catal.
1, 820–829 (2018).

A. Winiwarter et al., Energy Environ. Sci.
12, 1055–1067 (2019).

S. B. Scott et al., Catal. Sci. Technol. (2020).

A. Winiwarter et al., ChemElectroChem, in press.

Figure 1
Cation Co-Adsorption and Island Formation in the Electrochemical Environment
Authors: McCrum Ian T. , Koper Marc
Published: July 2021

The electrode/electrolyte interface is complex, and its composition, structure, and dynamics affect the rate and mechanism of electrocatalytic reactions. The presence of spectator cations near the electrode surface, for example, is well known to affect the rate and selectivity of carbon dioxide electroreduction, where changing from a lithium to a cesium cation can increase the selectivity of ethylene production on copper from 2% to 31% [1]. While many explanations of the mechanism of the effect of these alkali metal cations has been proposed, no one theory has been well accepted. In previous work, we have shown that alkali metal cations can sit close to an electrode surface, in particular at high pH and low potentials; further, once close to (“adsorbed” on) the surface, these spectator cations can then interact with and alter the adsorption energy of reactive intermediates, such as those present during CO2 electroreduction [2], or adsorbed hydroxide (OH*) on platinum (an intermediate in many electrochemical reactions) [3]. In this work, we find a cation which when present in an alkaline electrolyte has a large effect on the binding strength of hydroxide (larger than that of the alkali metal cations) on a Pt(111) electrode and causes a significant hysteresis in hydroxide adsorption/desorption. Using a combination of detailed experiments on a single crystal Pt(111) electrode and density functional theory simulations, we show that this hysteresis results from the co-adsorption of the cation and of hydroxide, with an interaction between the cation and hydroxide which is so strong that it drives island formation and a first order phase transition in the OH* adlayer. This provides direct evidence for cation (co)adsorption. Implications for electrocatalysis and electrolyte design will be discussed.

[1] M.R. Singh, Y. Kwon, Y. Lum, J.W. Ager III, A.T. Bell, J. Am. Chem. Soc.,
138, 13006-13012 (2016).

[2] S.A. Akhade, I.T. McCrum, M.J. Janik, J. Electrochem. Soc., 163, F477 (2016).

[3] I.T. McCrum, M.J. Janik, J. Phys. Chem. C, 120, 1, 457-471 (2016).
Adsorbate Molecular and Electronic Structure Effect on Metal-Adsorbate Interactions
Authors: Hasan Mohammad Hasibul , McCrum Ian T.
Published: July 2021

(Electro)catalysis is a powerful tool which can be used to produce fuels and chemicals, such as hydrogen and ammonia. Economical catalysis requires catalysts which are highly active, selective in producing the desired product, and inexpensive too. Meeting these design goals is challenging and requires intelligent catalyst design. Catalytic activity and selectivity is dictated by the relative energy and activation barriers between adsorbed reaction intermediates, which in turn are determined by how strongly these intermediates interact with the (electro)catalyst surface. Therefore, if we can unveil the mystery behind the driving forces for metal-adsorbate interaction, this could be a step forward towards predictive active & selective catalyst design. From the earlier works of B. Hammer et al. [1] & Federico Calle-Vallejo et al. [2] we know that some of the properties of metals, such as the energy of the metal d-bands, and the surface coordination number, determine how strongly a metal surface will bind to an adsorbate. However, we still do not have enough information on what properties of the adsorbate can influence this metal-adsorbate interaction. The goal of our research is to find what properties or parameters of an anionic adsorbate dictates the interaction between the anion and the metal surface. To bring some light into this, we have experimentally measured the adsorption strengths of a series of anions to an electrode surface and examined how the electronic or molecular structure of these anion adsorbates are correlated with changes in adsorption energies. We will also discuss possible descriptors for adsorption strength based on the structure of the adsorbate.

[1] B. Hammer, J.K. Norskov, Nature, 376, 238-240 (1995).

[2] F. Calle-Vallejo, J.I. Martínez, J.M. García-Lastra, P. Sautet, D. Loffreda, Angew. Chem. Int. Ed., 53, 8316-8319 (2014).
(Keynote) Metal Organic Framework for Photoelectrochemical Conversion and Electrochemical Energy Storage
Authors: Wu Nianqiang Nick
Published: July 2021

This talk presents our effort on metal organic framework (MOF) for photoelectrochemical conversion and energy storage. We have screened the metal cluster center to improve the electrochemical oxygen evolution reaction. We have also coated the MOF layer onto titanium oxide nanorod arrays toward photoelectrochemical oxygen evolution reaction. In addition, we have studied the charge transfer and mass transport during photoelectrochemical reactions. Last, we have designed a single-ion conducting MOF as a solid-state electrolyte for lithium-ion batteries.
Understanding the Self-Templating of Hierarchically Porous Carbon Electrocatalysts Using Group 2 Coordination Polymers
Authors: Farber Eliyahu , Eisenberg David
Published: July 2021

Self-templating of hierarchical porosity in carbon materials can be realized by the pyrolysis of well-designed metal-organic precursors. While this strategy is elegant and scalable, detailed mechanistic understanding of the self-templating process is lacking. We now present a systematic investigation of the microstructural evolution in porous carbons, including hierarchically micro-/meso-/macroporous materials with variable mesopore size. We focus on a homologous series of well-defined metal-organic coordination polymers, combining the highly abundant Group 2 ions (Mg2+, Ca2+, Sr2+, Ba2+) with a common ligand. To understand the role of the metal ion in directing the morphology of the ultimate N-doped carbons, we performed a detailed investigation using electron microscopy (HRSEM, HRTEM, EDS), N2 porosimetry, XRD, XPS and Raman spectroscopy. The rich morphological variations in the carbons determine their activity as metal-free electrocatalysts towards the oxygen reduction reaction. In particular, the reaction selectivity (2e
– vs. 4e
– pathways) is directed by competition between kinetics and mass transfer, due to confinement in mesopores.

Figure 1
(Keynote) Bio-Inspired Nano-Architectures for Artificial Photosynthesis
Authors: Bonchio Marcella
Published: July 2021

The perfect machinery of Natural Photosynthesis, powering our daily life with solar energy, is shaped by a modular network of photocomplexes, where molecular/nano-range order and distances are precisely tuned on membrane-bound compartments.1 Along these guidelines, the current frontier of Artificial Photosynthesis looks at a multi-component, interconnected system, where the cross-talk of photo-active and catalytic building blocks implements function and optimization/repair strategies.1 The expectation for man-made systems is to dissect the photosynthetic complexity and replicate its core-apparatus under a totally artificial environment, using cost-efficient synthetic strategies.2-4 In this scenario supramolecular strategies can play a crucial role to boost photo-assisted catalysis by a tailored interplay of non-covalent interactions, including hydrogen bonding, hydrophobic and electrostatic forces. Building on these concepts we report herein the functional characterization of photosynthetic nano-patterns emerging from the combination of water soluble photosensitizers with oxygenic polyoxometalates (POMs) known as the inorganic analogs of the natural PSII-OEC.5

A. Sartorel, M. Prato, M. Bonchio et. al., Energy Environ. Sci.
2012,
5, 5592.

S. Piccinin, A. Sartorel, M. Bonchio, S. Fabris et. al. PNAS
2013, 110, 4917.

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2009, 131, 16051.

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2010, 2, 826.

M. Bonchio, A. Sartorel, M. Prato et al. Nature Chemistry
2019,
11, 146.
Continuum Approach for Studying Morphological Deformations of Multiple-Phase Organic Photovoltaic Cells
Authors: Shapira Alon Z , Gavish Nir , Uecker Hannes , Yochelis Arik
Published: July 2021

Optimizing the properties of the mosaic morphology of bulk heterojunction (BHJ) organic photovoltaics (OPV) is not only challenging technologically but also intriguing from the mechanistic point of view. Among the recent breakthroughs in studies of BHJ morphology, is the identification and utilization of a three-phase (donor/mixed/acceptor) BHJ, where the (intermediate) mixed-phase can inhibit morphological changes, such as phase separation. Using a continuum approach, we develop and analyze a model that undertakes the coupling between the spatiotemporal evolution of the material and charge dynamics along with charge transfer at the device electrodes. Starting from an ideal BHJ represented by stripes, we reveal and distinguish between generic mechanisms that alter the evolution of stripes: the bending (zigzag mode) and the pinching (cross-roll mode) of the donor/acceptor domains. We then emphasize that the latter instability mode, is notorious as it leads to the formation of disconnected domains and hence to loss of charge flux. Consequently, the analysis implies that donor-acceptor mixtures with higher mixing energy are more likely to develop pinching under charge-flux boundary conditions. We believe that these results provide a qualitative roadmap for morphological BHJ optimization, using mixed-phase composition and moreover, open new vistas to application involving three phase morphologies, such as ion-intercalated rechargeable batteries.
In Situ Electrochemical AFM: Travelling Waves and Pit Growth during Au Dissolution
Authors: Gao Qingyu
Published: July 2021

Kinetics, mechanism and self-organization evolution during electrochemical dissolution of gold (gold leaching) in acidic thiourea or alkaline thiosulfate solutions can be clarified through in Situ electrochemical (EC) AFM at the mesoscopic level. Pit-induced layer dissolution and travelling waves as well as the transition from pit-induced layer dissolution to wave-type dissolution could be observed by using in situ EC-AFM at open-circuit potential (OCP) of Au(111) bead electrode in acidic thiourea solutions. A proposed scheme gives an interpretation for the pit-induced layer and wave dissolution of Au(111) through the bonding interaction of sulfur atoms with gold atoms located at different positions on Au(111). Pits and pit-induced layer dissolution of Au(111) plane could be observed through in situ EC-AFM as the potential applied potentiostat above OCP in cupric ammoniacal thiosulfate solutions, where the pits dissolution present autocatalytic growth in depths, radius and numbers. The role of copper(II) anions and ammonia during the electrochemical dissolution of Au(111) plane is to dissolve the passivated sulfur comes from the decomposition of thiosulfate or chemical dissociation of polythionates produced by thiosulfate on the surface of Au(111) bead electrode, rather than to oxidize Au0 to Au+ for copper(II) ammonia complex according to the our study with in Situ EC-AFM.
Micro-Kinetic Modelling of the Electro-Oxidation of Methanol on Platinum
Authors: Paredes Salazar Enrique Adalberto , Calderón Cárdenas Alfredo , Varela Hamilton
Published: July 2021

Methanol electro-oxidation reaction is a widely studied system due to its applicability in electrochemical devices for energy conversion, such as direct methanol fuel cells. Nevertheless, the effect of some kinetic parameters on the overall reaction rate is still unclear and the reaction mechanism is controversial. Herein we investigate the electro-oxidation of methanol on platinum by means of a micro-kinetic approach using the mean-field approximation. The resulting model, c.f. Figure 1, is based on data, namely spectroscopic and electrochemical, available in the literature, and translated into a set of ordinary differential equations. Simulations are carried out in comparison with experimental results, including cyclic voltammetry, chronamperometry and potential oscillations under galvanostatic control. The numerical simulations agree satisfactorily with the experimental results with a set of realistic reaction rates in the elemental reaction steps for the electrooxidation of methanol in platinum. The values of the rate coefficients show the adsorption of methanol and the first steps after the formation of formic acid as the fastest, while the desorption of bridge adsorbed formic acid and the chemical adsorption and desorption of methylformate as the fastest steps.

Figure 1
In-Situ X-Ray Absorption Spectroscopy Study of Electrocatalytic Reduction of Carbon Dioxide with Molybdenum Disulfide
Authors: Kumar Khagesh , Majidi Leily , Misal Saurabh , Salehi-Khojin Amin , Cabana Jordi
Published: July 2021

Electrocatalytic reactions offer alternative routes for the conversion and storage of energy. For instance, the electrocatalytic reduction of carbon dioxide could lead to energy-rich syngas, methanol, or even hydrocarbons. Layered transition metal dichalcogenide nanomaterials, such as MoS2, have emerged as electrocatalysts towards CO2 reduction with high efficiency and low overpotentials. However, the underlying chemical and electronic states defining the catalytic activity have not yet been completely defined. These key states can be probed for both metals and ligands in selected MX2 (M=W, Mo; X=S, Se) using synchrotron-based X-ray absorption spectroscopy (XAS). In recent work we performed in-situ XAS measurements at Mo K-edge and S K-edge for MoS2 nanosheets. Measurements at the S K-edge showed drastic changes at the pre-edge and edge indicating changes in number of available unoccupied states and Zeff respectively. On the other hand, only a small shift of the Mo K-edge was observed. Metal d-states are found to be the active site for catalysis, yet the ligand K-edge presents a better method to examine catalytic processes. Since the pre-edge reflects a transition to metal-ligand hybridized states, its intensity and position gives direct insight into the activity and changes of d-states. Given the vast compositional space of metal and ligand for MX2, the knowledge of how d-state activity will serve to pave the way to a better study of metal and chalcogenide combinations to improve the electrocatalytic performance.

Figure 1
(Invited) Mapping Electrode and Electrolyte Heterogeneity with High Energy Synchrotron Diffraction
Authors: Fister Tim , Kinnibrugh Tiffany , Wolfman Mark , Bazak J. David , Murugesan Vijay , Chalasani Subhas , Scott Jack , Smith Kevin , Hesterberg Travis , Raiford Matthew , Ellis Tim
Published: July 2021

Lead acid batteries are often portrayed as a mature technology with limited capacity and room for innovation. In reality, lead batteries have significant room for growth since they only utilize a fraction of their active material and have been engineered for SLI applications that lack a battery management system for controlled charge and discharge. In large part these issues are related to chemical heterogeneity that exists at both the pack level and within the battery electrode microstructure. Unlike a lithium ion battery, lead acid electrodes are typically larger laterally and millimeters thick with significant porosity to allow acid penetration. At the particle level, the growth and dissolution of PbSO4 during discharge from the Pb and PbO2 charge species also leads to significant volume change and swings in local acid concentration within the electrode pores. Recently, we have begun analyzing the spatial variation of charge acceptance in lead acid cells using high energy x-ray diffraction. At energies approaching the lead K-edge (88 keV), x-rays can penetrate through several millimeters of active material. This allows chemical mapping across 2 V cells during formation and cycling and even depth profiling on miniaturized batteries. In situ diffraction provides valuable new information on microstructural changes in phase and crystallite size during these precipitation and growth reactions. Surprisingly, scatter from noncrystalline phases – i.e. the electrolyte – can also be measured by analyzing changes in the broad background underlying the strong Bragg peaks. While the average state of charge (SOC) computed from diffraction species closely matches the electrochemistry, diffraction mapping shows that the charge state and the degree of charge acceptance can vary substantially throughout each electrode. In general, we find strong gradients in SOC and electrolyte concentration that grow from the lead current collector during formation and initial cycling. In larger cells, we also find vertical heterogeneity that develops over repeated cycling. Combined with ongoing electrochemical modeling and innovations in electrode architectures, these results are helping improve utilization and cyclability, developing lead acid into a stronger contender for emerging stationary storage applications.
(Invited) Operando Characterization of Transient Material Changes in Battery Cathode Materials By X-Ray Diffraction and Spectroscopy
Authors: Gallaway Joshua W
Published: July 2021

Operando characterization of battery materials provides several benefits. For example it eliminates the chance that materials are oxidized or further transformed during removal from the cell and sample preparation, and increases the odds that short-lived material changes and intermediate species can be observed and correlated to electrochemical data. Receiving adequate experimental signal from complicated electrochemical cells can be problematic, and the use of synchrotron light is one solution. X-rays with high brightness, flux, or energy can provide data that is adequately temporally (and sometimes spatially) resolved to correlate material changes with cycling data. This talk will present characterization by both X-ray diffraction and X-ray absorption spectroscopy, which provide information about long-range and short-range structural order respectively.

The first example is that of a sulfide all solid-state cathode that is a composite of FeS2, conductive carbon, and Li6.6Ge0.6Sb0.4S5I solid electrolyte (SE).1 Voltage stability window of sulfide SEs is a critical issue, and we directly observe crystal structure distortion of the SE that occurs during discharge. This occurs in the cathode but not elsewhere in the cell, and is reversible provided a minimum potential limit is not passed (see Figure 1). Given the air and moisture sensitivity of the SE, experiments had to be performed within the sealed cell, under significant applied pressure. Operando energy-dispersive x-ray diffraction (EDXRD) allowed data to be collected from buried locations in the bulk of intact and sealed batteries during cycling.2

The second example is that of a rechargeable alkaline Bi-modified MnO2 cathode, in which both Bi and Mn are electrochemically active and provide cycled capacity. The mechanism of MnO2 cycling is complex, first involving insertion of cations into the layered structure, followed by conversion to a new structure. By using rapid collection of X-ray absorption near edge structure (XANES) data at the Mn K-edge and Bi LIII-edge, an interaction between Mn and Bi was identified during early stages of the charging step.3 This gives insight into the cycling mechanism that makes rechargeability possible.

Acknowledgments

This work was supported by the U.S. Department of Energy (DOE) Office of Electricity Delivery and Energy Reliability, Dr. Imre Gyuk, Energy Storage Program Manager. We also acknowledge financial support from the National Science Foundation under Award Number CBET-ES-1924534.

References

Sun, X.; Stavola, A.M.; Cao, D.; Bruck, A.M.; Wang, Y.; Zhang, Y.; Luan, P.; Gallaway, J.W.; Zhu, H., Advanced Energy Materials,2020, 2002861.

Marschilok, A. C.; Bruck, A.; Abraham, A.; Stackhouse, C.; Takeuchi, K. J.; Takeuchi, E. S.; Croft, M.; Gallaway, J.W., Physical Chemistry Chemical Physics, 2020, 22, 20972-20989.

Bruck, A.M.; Kim, M.A.; Ma, L.; Ehrlich, S.N.; Okasinski, J.S.; and Gallaway, J.W., Journal of the Electrochemical Society,
2020,
167, 110514.

Figure 1
Highly Stable Co3O4 Nanofibers in Alkaline Oxygen Evolution Reaction
Authors: Aljabour Abdalaziz
Published: July 2021

Electrocatalysis of hydrogen and oxygen evolution is an essential route in performing renewable and sustainable energy alternatives. Although hydrogen technologies are largely advanced, the oxygen electrochemistry is mainly limited due to the complexity in seeking suitable and stable electrocatalysts, in unifying electrolytic conditions and hence sluggish reaction kinetics. Herein, we demonstrate the electrocatalytic activity of the nanofibrous cobalt oxide in alkaline oxygen evolution reaction with a generous operation lifetime of 120 hours. The unique and facile preparation pathway of fibers by electrospinning allows enlarged electrode networking and nanofibrous interaction thus leading to extended catalytically active surface area, imperative for well-performing electrolysis. Operating at low overpotential of 293 mV at a current density of 10 mA cm- 2, as well as low Tafel slope of 60.5 mVdec-1 in 1M KOH prove the efficient utilization of nanofibrous Co3O4 electrocatalyst towards oxygen evolution with an excellent long-term stability over 100 hours.[1]

[1] A.A., Long-Lasting Electrospun Co3O4 Nanofibers for Electrocatalytic Oxygen Evolution Reaction, ChemistrySelect 2020, 5, 748, doi.org/10.1002/slct.20.