bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Dye-Sensitized Oxide Nanosheets for Visible-Light Water Splitting
Authors: Maeda Kazuhiko
Published: July 2021

Metal oxide nanosheets derived from the layered counterparts have attracted attention in various fields due to their unique structural properties. The anisotropic feature of nanosheets, having a thickness of ~1 nm and lateral dimensions ranging from several hundred nanometers to a few micrometer, is advantageous for heterogeneous photocatalysis, as the diffusion length of photogenerated carriers to the surface is shortened, leading to higher activity.

It is also known that certain nanoparticulate metals or metal oxides on a semiconductor photocatalyst work as cocatalysts to promote water reduction and/or oxidation. In heterogeneous photocatalysis, the effect of cocatalyst size on the water-splitting performance had not been examined at sizes smaller than 1 nm due to the lack of an effective preparation method and a suitable photocatalyst. We have demonstrated that metal nanoclusters (such as Pt) of <1 nm in size could be deposited on the interlayer nanospace of KCa2Nb3O10 using the electrostatic attraction between a cationic metal complex and a negatively charged Ca2Nb3O10
– sheet, without the aid of any additional reagent. The material obtained exhibited 8 times greater photocatalytic activity for overall water splitting under band-gap irradiation than the previously reported analog using a RuO2 promoter. This study highlighted the superior functionality of <1 nm Pt nanoclusters for photocatalytic overall water splitting.

With further modification by a ruthenium(II) photosensitizer, this material also worked as a H2 evolution photocatalyst in visible-light-driven Z-scheme water splitting, in combination with a WO3-based O2 evolution photocatalyst and a triiodide/iodide redox couple. Pt-intercalated HCa2Nb3O10 nanosheets further modified with amorphous AlO
x
clusters demonstrated a remarkable photocatalytic activity with a dye-based turnover number and frequency for H2 evolution of 4580 and 1960 h–1, respectively, which were by far the highest among dye-sensitized nonsacrificial photocatalytic systems ever reported.
(Invited) Copper Kesterite Photocathode for Photoelectrochemical Water Splitting
Authors: Wong Lydia Helena
Published: July 2021

Copper kesterite, Cu2Zn(S,Se)4, with tunable bandgap between 1.1 – 1.7eV, is one of the most promising candidates for emerging thin film solar cell. It also has many suitable attributes of a photocathode for photoelectrochemical solar water splitting such as good absorption coefficient and conduction band maximum > H2O/H2 reduction potential. However the photocurrent and onset potential are relatively poorer due to tendency of forming deep defects associated with Cu, Zn, Sn antisites and interfacial defects. In this talk, I will present our group’s efforts in eliminating these defects by cation substitution. We found that partially substituting Zn with Cd improved its carrier mobility and lifetime and resulted in 4x enhancement of photocurrent. Ag partial substitution of Cu resulted in reduced defects at the CZTS/CdS interface and led to better onset potential. Finally, we show the use of transparent conducting oxide which not only improves the electron transport to the electrolyte, but also improves the long term stability of the photocathode.
Ligand Engineered Metal−Organic Frameworks for Electrochemical Reduction of Carbon Dioxide to Carbon Monoxide
Authors: Al-Attas Tareq A. , Marei Nedal N. , Yong Xue , Yasri Nael , Siahrostami Samira , Shimizu George , Thangadurai Venkataraman , Kibria Md Golam
Published: July 2021

The economic feasibility of electrocatalytic carbon dioxide reduction reaction (CO2RR) relies on the development of highly selective and efficient catalysts operating at a high current density. Herein, we explore a ligand engineering strategy involving the use of metal-organic frameworks (MOFs) and combining the desirable features of homogeneous and heterogeneous catalysts for boosting the activity of CO2RR. Zn-based MOFs involving two different azolate functional ligands i.e., 1,2,4-triazole (Calgary Framework-20, CALF-20) and 2-methylimidazole (zeolitic imidazolate framework-8, ZIF-8) were investigated for CO2RR in an alkaline flow cell electrolyzer. The highest CO partial current density of 53.2 mA/cm2 was observed for a Zn-based MOF (CALF-20). CALF-20 showed the highest reported Faradaic efficiency of Zn-based MOFs for CO production (ca. 94% at -0.969 V vs. reversible hydrogen electrode, RHE), with a TOF of 1360.8 h-1 and a partial current density -32.8 mA/cm2. Experimental and density functional theory (DFT) results indicate that the sp2
carbon atoms in azole ligands coordinated with the metal center in the MOFs are the active sites for CO2RR, due to the fully occupied 3d orbital of Zn(II) centers. Ab initio investigation shows that both azolate frameworks in CALF-20 and ZIF-8 have most favorable adsorption sites at the N−sp2
C. Adopting the triazole ligand in CALF-20 enhances the charge transfer (as compared with diazole group in ZIF-8), which induces more electrons in the adjacent active sites at the azole ligand and facilitates *COOH formation, boosting the current density and Faradaic efficiency towards CO production. This study suggests that ligand engineering in MOFs could be a viable approach to design highly efficient CO2RR catalyst.
(Invited) Enable Efficient Solar Driven CO2 Reduction with Stable and Highly Active Oxygen Evolution Catalyst in Neutral pH
Authors: Jia Hongfei , Zhou Li , Chen Ling
Published: July 2021

Using electricity generated from solar cells, conversion of water and CO2 to syngas in an electrolytic cell mimics the photosynthesis process and provides a facile pathway to the production of various chemicals and liquid fuels.1 Development of new oxygen evolution reaction (OER) catalysts that are both active and stable in neutral pH is highly desired for such a process to avoid the complication of managing the pH gap between CO2 reduction on the cathode and water oxidation on the anode. Over the last several years, we have investigated various transition metal oxides as potential candidates for OER for artificial photosynthesis, including CoWO4, Li2CoGeO4 and various perovskites.2-4 It has been revealed that these catalysts were not stable in neutral pH and subjected to degradation either thermodynamically or kinetically.

In this presentation, we report a new brownmillerite OER catalyst, Sr2GaCoO5 (SGC), with superior performance and durability. At pH 7.0, the catalyst has a specific activity about 7.8-18.3 times higher than that of IrO2 at the applied electrode potentials between 1.53-1.73 V vs. RHE. With a catalyst loading of 1 mg/cm2, the measured overpotential was only 0.38 V at a current density of 10 mA/cm2, which maintained unchanged over the testing period of 72 hrs. A comparative study against Sr2AlCoO5 indicates the excellent stability of SGC is related to the presence of gallium oxide in the crystal structure, which may help prevent SGC from dissolution under the OER operation condition in neutral pH, although detailed mechanistic understanding should be further developed by additional studies in the future. Combining this novel OER catalyst with an anodized silver cathode and a triple junction of GaInP/GaInAs/Ge photovoltaic, the CO2 reduction system demonstrated a solar-to-CO energy conversion efficiency of 13.9% over a period of 19 hrs with no appreciable performance degradation.5 This result has shown that artificial photosynthesis can indeed be more efficient than the natural photosynthesis process for CO2 reduction, and should play an important role in addressing the challenges of global warming and climate change.

References:

Chem. Commun. 51, 17704–17707 (2015)

RSC Adv.
2(29), 10874-10881 (2012)

Mater. Chem. A. 2(43): 18428-18434 (2014)

Chem. Chem. Phys., 17, 22576-22580 (2015).

Nat. Commun. 10
, 4081 (2019)
(Invited) Electrochemical CO2 Reduction Reaction to C2 Chemicals with Cu-Based Nanocatalysts
Authors: Hwang Yun Jeong
Published: July 2021

Cu is an interesting electrocatalyst for CO2 reduction reaction (CO2RR) due to its unique capability to produce various hydrocarbon chemical in addition to H2, and the nanostructures of Cu surface significantly affect the product selectivity for C2+ over C1 chemicals. Although material engineering strategies have aimed at the design of a selective C2+-producing catalyst, the role of the fundamental descriptor allowing control of the desired pathway is not yet well-understood. In this context, reliable guidelines for highly selective reactions require understanding the catalyst material and characterization. Both of a H-cell and gas-diffusion-electrode (GDE) based gas-fed cells have shown the enhanced ethylene selectivity with Cu nanoparticles prepared by oxide forms. The fragmented Cu surfaces having high defects or grain boundaries are proposed as active sites for C-C coupling based on the material characterization. In addition, in-situ spectroscopy such as X-ray absorption spectroscopy, Raman spectroscopy, and infrared absorption spectroscopy can provide additional information of the catalyst and intermediate operando condition. We demonstrated that there are active sites that activate the dimerization of CO, and C-C coupling occurs exclusively by CO dimerization, without the participation of *CHO which is proposed as an intermediate for CH4 production. We expect that these findings will aid the understanding of the CO2RR mechanism, and that the disclosed structures and kinetics of the surface intermediates will enable the design of improved catalysts for future CO2RR.
(Invited) Photoelectrochemical Reduction of CO2 at Poly(4-vinylpyridine)-Stabilized Copper(I) Oxide Semiconductor Decorated with Palladium Cocatalyst
Authors: Kulesza Pawel J. , Szaniawska Ewelina , Seta-Wiaderek Ewelina , Wadas Anna , Rutkowska Iwona , Rajeshwar Krishnan
Published: July 2021

Poly(4-vinylpyridine)-modified copper(I) oxide photocathodes, bare or decorated with palladium nanoparticles, can be used for the visible-light-driven selective reduction of CO2, mostly to carbon monoxide (in the absence of Pd co-catalyst) and methanol (in the presence of Pd co-catalyst). The photocathode materials, which are composed of hierarchically deposited (onto transparent fluorine-doped conducting glass electrode) Cu2O (inner layer) and poly(4-vinylpyridine), P4VP, polyelectrolyte film (outer-layer), with or without dispersed Pd-nanoparticles, have been fabricated and, subsequently, examined using electrochemical methodology, atomic force microscopy and various spectroscopic techniques, including Raman approach. While the physicochemical characteristics of Cu2O, including the oxide identity and its semiconducting properties, are not largely affected by the interfacial modification with P4VP, the photostability of the hybrid photocathode is significantly improved. The P4VP-modified Cu2O photocathodes exhibit reasonable durability during photoelectrochemical reduction of CO2 upon illumination with sunlight in semi-neutral medium (Na2SO4). On the whole, the photoelectrochemical reduction of CO2 proceeds at potentials starting from ca 0.55 V (vs RHE), which are substantially (almost 800 mV) more positive, in comparison to those characteristic of the conventional electrochemical reduction in the dark. Introduction of palladium co-catalyst seems to improve distribution (collection and transport) of photoelectrons at the photoelectrochemical interface and affects the CO2-electroreduction mechanism.
Ammonia Generation from 2D MoS2 Catalysts
Authors: Miller-Link Elisa , Attanayake Nuwan , Zhang Hanyu , Metzroth Lucy
Published: July 2021

We use metallic MoS2 as a catalyst for N2 fixation and NH3 generation. Based on the current literature with regard to MoS2 catalytic performance for NH3 generation, it is tracking with catalytic performance for hydrogen evolution. For example, if you increase edge sites with 2D MoS2 structuring or incorporate more vacancies/defect sites, the hydrogen evolution reaction improves. The same is true of NH3 formation. If we take this one step further, hydrogen generation further increases if MoS2 is converted to its thermodynamically unstable metallic state and is stabilized in this state with functional groups. Therefore, we extend this correlation to NH3 generation. We expect that the N2 fixation and NH3 generation will improve and be stable if we use metallic, functionalized MoS2 nanosheets. This hypothesis is tested and reported. We will also comment on the selectivity for the H2 versus NH3 generation from this catalyst with various functional groups.
(Invited) High-Rate Ammonia Synthesis at Non-Aqueous Gas Diffusion Electrodes
Authors: Manthiram Karthish
Published: July 2021

The Haber Bosch process has served as the dominant method of synthesizing ammonia over the last century. Ammonia produced through this route leads to a stoichiometric carbon dioxide footprint and also involves harsh conditions which limit modularity of the process. We are developing a continuous lithium-mediated approach through which nitrogen can be fixed at ambient conditions while eliminating the carbon dioxide footprint. We have elucidated the reaction network through which ammonia synthesis occurs in competition with hydrogen evolution. The coupling of kinetics and transport has a significant influence on the rates of ammonia synthesis, providing a means to improve selectivity of nitrogen fixation through non-aqueous gas diffusion electrodes.
Electrochemical Nitrogen Reduction Reaction over Subnano-Clustered Ruthenium Catalysts: A DFT Study
Authors: Kim Seung-hoon , Yoo Geunsang
Published: July 2021

The electrochemical nitrogen reduction reaction (NRR) for ammonia production is one of the most spotlighted chemical process for hydrogen storage and transportation. We investigated NRR on the ruthenium-based subnano-clustered catalysts embedded in modified defective graphene (Rux/YC, Ru : ruthenium, x : 1 to 3, Y : boron, carbon, and nitrogen, C : graphitic carbon) using density functional theory (DFT) calculation.

We identified the energetically optimized structures of Rux/YCs among all possible geometries. Also we calculated the dissociative adsorption free energy of nitrogen (ΔGDiss) to determine which mechanism to follow for NRR on Rux/YCs. We also calculated the adsorption energy (ΔEAds) of all possible reaction intermediates to identify the detailed mechanism and the limiting potential for NRR on each catalyst. Additionally, we compared the reaction potential for NRR and hydrogen evolution reaction (HER) by calculating the adsorption free energy of H*.

In the Rux/C catalysts, ΔEAds of N* tend to become stronger and the ΔGDiss decreased, as the number of Ru atoms increased. In contrast, the reverse tendency was shown in Rux/BC catalysts between ΔGDiss and the number of Ru atoms. In the Rux/NCs, ΔGDiss for the two Ru atoms was lowest. Overall, NRR follow the dissociative mechanism on the Ru3/C, Ru1/BC, and Ru2/BC catalysts, and association mechanism on the others.

As shown in figure below, single-atomic Ru1/YCs showed obviously lower NRR potential than double- and triple-atomic Rux/YCs. In the case of Rux/C and Rux/NC, it was due to the relatively weak adsorption of N2H*. However, in Ru1/BC, the ΔEAds of N2H* was so strong that the reaction potential was relatively higher than Ru2/BC and Ru3/BC due to the strong B-N bonding. It was found that the ΔEAds of N2H* can be used as an indicator to predict NRR potential on Rux/YCs.

We compared the reaction potential for NRR and HER on each catalysts. In Ru2/NC catalyst, HER potential was lower than NRR potential, and it was found that Ru2/NC with good activity and selectivity is the most promising candidate for NRR catalyst.

Figure 1
Proton-Conducting Ceramics for Electrochemical Ammonia Synthesis
Authors: Herradon Carolina , Le Long , Meisel Charlie , Cadigan Chris , O'Hayre Ryan , Sullivan Neal P.
Published: July 2021

We report our progress in developing proton-conducting ceramics for flexible storage of intermittent renewable electricity in the form of ammonia. Various electrochemical and thermochemical synthesis strategies have been investigated in pursuit of “green ammonia”. Electrochemical ammonia synthesis can harness water-splitting to source hydrogen, displacing steam-methane reforming widely used in conventional ammonia production through the well-established Haber-Bosch process (HB).

This electrochemical approach potentially provides an efficient solution to the energy-storage challenges presented by the expanding market penetration of solar and wind power. The intermittent nature of these renewables presents strain on the conventional power plants tasked with stable electricity production. Through creative application of novel proton-conducting electroceramics, intermittent renewable electricity can be used to drive the synthesis of green ammonia, effectively storing electricity in the form of an easily transported, carbon-neutral, energy-dense commodity chemical. Further, the process is reversible; NH3 can be electrochemically re-converted back into electricity as needed in meeting peak load demands.

Displacing Haber-Bosch proves challenging, as it requires process solutions that can simultaneously achieve high NH3 conversion and high NH3-synthesis rate while minimizing energy costs. The Haber-Bosch process achieves both through high-pressure operation (up to 300 bar), where thermodynamics are more favorable. Electrochemical systems have yet to reach this stage of technological development. All previous work has been limited to atmospheric-pressure operation, where NH3-synthesis rates are orders-of-magnitude lower. Further, most reports on electrochemical ammonia synthesis have utilized molecular H2 as the source of protons for NH3 synthesis, rather than water electrolysis as described here.

In this work, we present our efforts to apply proton-conducting ceramics to enable electrochemical ammonia synthesis from H2O and N2 feedstocks. Protonic ceramics are emerging materials finding applications in efficient electricity generation, energy storage, and fuels synthesis. As shown in the figure, renewable electricity is used to drive hydrogen production through high-temperature water splitting in the protonic-ceramic electrolyzer. The hydrogen mixes with nitrogen and is then converted to NH3 over a ruthenium catalyst. The process is executed at pressures up to 12 bar, bringing significant challenges in packaging of the protonic ceramic and the catalyst. In this presentation, we review our progress in establishing pressurized operation, and the benefits it brings to electrochemical synthesis of ammonia.

Figure 1
(Invited) Intermediate Temperature Direct Ammonia Fuel Cell Using Alkaline Electrolyte System
Authors: Lattimer Judith , Xu Hui , McCatty Steve , Mohan Yamini
Published: July 2021

Ammonia is a very attractive carbon-neutral fuel due to its low cost, high energy density, and existing transportation infrastructure. However, the viable commercial application of direct ammonia fuel cells (DAFC) has not been realized, largely due to materials challenges that lead to poor cell performance. Generally, DAFCs either use low temperature polymer electrolytes, which are limited by low reaction rates and severe ammonia crossover, or use high temperature solid oxide electrolytes, which suffer from severe material thermal degradation. We have developed an intermediate temperature alkaline electrolyte-based DAFC that operates at 400-600 °C, enabling high reaction rates while limiting thermal degradation. This DAFC is based on our innovative molten hydroxide electrolyte impregnated in a porous ceramic matrix, which has conductivity as high as 0.4 S/cm at 350 °C, enabling rapid hydroxide transport. The DAFCs uses state-of-the-art ammonia oxidation catalysts and ammonia-tolerant oxygen reduction reaction catalysts. Our DAFC has demonstrated an OCV of 1.2 V and can achieve 300 mA/cm2 at 0.86 V at 550 ⁰C, and 0.98 V at 600 ⁰C, or >450 mW/cm2 power from pure humidified ammonia. It has low ammonia crossover, thus enabling the high OCV and high power density without catalyst poisoning. Further work on catalyst development and cell design is underway to achieve higher power densities and reduce PGM catalyst loading and operation temperature, making this a more commercially viable technology.
D–Band Contraction of Metal Nitride Nanosheets Enables Highly Efficient and Stable Electrochemical Oxidation of Ammonia
Authors: He Shi , Liu Jie , Chen Yufeng , Wang Mengdi , Nuomin Hanggai , Zhu Siyuan
Published: July 2021

Ammonia is a promising hydrogen carrier as it reduces the cost of long–range transportation of hydrogen. Ammonia electrolysis provides a convenient method to extract hydrogen from ammonia at end users. However, the conventional platinum carbon electrode suffers from fast degradation and electrode fouling at electrode–electrolyte interface during the ammonia electrochemical oxidation(AOR). Here, we report that nitriding electrochemical deposited nickel cobalt layered double hydroxide nanosheets can achieve high electrocatalytic activity for AOR in non–aqueous solution. The AOR onset overpotential of NiCo2N nanosheets is 0.55 V which is about 0.25 V lower than that of the platinum carbon electrode. Ultraviolet–visible and Mass spectroscopy studies reveal NiCo2N nanosheets can suppress the formation of metal amine complex and preferentially oxidize ammonia to N2 with a faradic efficiency of over 90 percent. DFT calculation indicates that the downshift of the metal d–band center on NiCo2N nanosheets surface accelerated the generation of NH+
X cations and desorption of final N2*, boosting ammonia electrochemical oxidation toward N2. Overall, this work introduces a practical strategy for synthesizing an active and stable electrocatalyst for AOR.
Design of Bioelectrochemical Conversion Tool from Food and Human Waste to Electrical Energy Using Microbial Fuel Cell (MFC) Based on Internet of Things
Authors: Baladraf Thabed Tholib
Published: July 2021

The increase in world population is in line with the increase in the amount of energy demand, especially electricity. However, the energy used today is still using fossil energy, which one day will run out. Dependence on non-renewable energy causes weak energy resistance, resulting in electricity scarcity. Microbial fuel cells (MFC) can be a new alternative energy source because they can generate electrical energy by utilizing the interactions of bacteria found in nature. To fulfill electricity needs, researchers created a tool that can generate electrical energy by utilizing food waste and human waste as a substrate which is converted into electrical energy through the bioelectrochemical activity of electrons and protons by bacteria. The tool is integrated with the internet of things as an effort to use technology so that it can control temperature and voltage automatically. This research was aimed to determine the design of a tool to convert food waste and human waste into clean renewable electrical energy, determine the working principle of the tool, determine the efficiency of the tool in producing electrical energy, and determine the potential of the tool to meet electricity needs. The research was carried out using 3 variations, namely variation 1 (zinc and cathode), variation 2 (food waste, human waste, and water), variation 3 (carbon, cathode, nutrient broth, electrolyte solution, food waste, and human waste). The tool created is portable with a DC voltage of 12 V to AC 220 V 500 W and the best results are obtained from variation 3 with 26.6 volts from 1.8 liters of food waste and human waste to obtain a voltage efficiency of up to 95%. This tool has the potential to overcome the electrical energy crisis and fulfill people's electricity needs by utilizing food waste and human waste.
Electrolyte-Coordination-Induced Electrochemical Multiple Electron Oxidation of 2,5-Diarylthiophenes
Authors: Shida Naoki , Maekawa Takuma , Tomita Ikuyoshi , Inagi Shinsuke
Published: July 2021

Chalcogenophene is a five membered aromatic ring containing group 16 elements, and widely used for the design of small molecule or polymer based organic devices. Previously, we have reported a thorough discussions on the electrochemical redox chemistry of tellurium-containing chalcogenophenes, tellurophene (N. Shida, H. Nishiyama, F. Zheng, S. Ye, D. S. Seferos, I. Tomita, S. Inagi, Communications Chemistry, 2019, 2, 124.). We found that the electrochemical oxidation of 2,5-diaryltellurophene in non-coordinating electrolyte resulted in one-electron oxidation product, while two-electron oxidation preferably proceeded in coordinating electrolyte. These results suggest that the design of electrolyte crucially affect the redox chemistry of chalcogenophenes.

In this study, we report that the electrochemical redox behavior of 2,5-diarylthiophene also varies significantly depending on the coordination of the electrolyte. Specifically, we have found that the coordination of the electrolyte alters the number of electrons in the oxidation of 2,5-diarylthiophene. It was also found that the species generated by the multiple electron transfer in coordinating electrolyte showed a unique reactivity, and proceeded to an unprecedented dimerization reaction to give sulfonium salts.
Distance Dependence of Electron Transfer through Conformationally Constrained Peptides
Authors: Antonello Sabrina , Maran Flavio
Published: July 2021

Understanding and the ability of peptides to mediate long-range electron tunneling in proteins is an evergreen topic. In this context, the study of electron transfer (ET) through model peptides has been particularly useful, especially to assess the occurrence (or competition) of the superexchange and sequential hopping mechanisms as a function of the structure and length of the peptide bridge. In previous studies [1,2], we stressed the importance of dealing with peptides with a well-defined and rigid structure to properly correlate kinetic and structural data. This structural control was made possible by using model peptide bridges based on oligomers of the α-aminoisobutyric acid (Aib) residue. The Aib unit is characterized by a marked steric hindrance at the α-carbon, and this allows the preparation of very rigid peptides. Rigidity is ensured by a framework of intramolecular C=O···H-N hydrogen bonds. Consequently, these peptides possess a strong dipole moment along the main axis [3]. In previous studies, we used cyclic voltammetry to study the dissociative ETs in two series of Donor − Aib-peptide − Acceptor systems in which we changed the donor group, whereas the acceptor was kept constant (a dialkyl peroxide moiety, resulting in the cleavage of the O-O peroxide bond [4]). In this communication, we describe the outcome of dissociative ETs carried out using a new series of Donor − Aib-peptide − Acceptor system in which the acceptor was a perbenzoate moiety [5]. This change also affects the dissociative ET driving force. The same peptide-length dependent dissociative ETs were tested for a possible solvent effect.

References

[1] Antonello, S.; Formaggio, F.; Moretto, A.; Toniolo, C.; Maran, F. J. Am. Chem. Soc.
2003, 125, 2874.

[2] Polo, F.; Antonello, S.; Formaggio, F.; Toniolo, C.; Maran, F. J. Am. Chem. Soc.
2005, 127, 492.

[3] Gobbo, P.; Antonello, S.; Guryanov, I.; Polo, F.; Soldà, A.; Zen, F.; Maran, F. ChemElectroChem
2016, 3, 2063.

[4] Antonello, S.; Venzo, A.; Maran, F. J. Electroanal. Chem.
2011, 660, 234.

[5] Zuliani, C.; Formaggio, F.; Scipionato, L.; Toniolo, C.; Antonello, S.; Maran, F. ChemElectroChem
2020, 7, 1225.
Electrochemical Characterization of Carboplatin at Unmodified Platinum Electrodes and Its Application to Drug Uptake Studies in Ovarian Cancer Cells
Authors: Luu Huy Tran Le , Nachtigal Mark W. , Kuss Sabine
Published: July 2021

Epithelial ovarian cancer affects approximately 240,000 women worldwide with an estimated of 152,000 deaths per year. Common treatments include surgery or chemotherapy using a combination of carboplatin and taxane. Unfortunately, approximately 75% patients relapse within 18 months. Of these relapsed patient, an estimate of 85% experience carboplatin resistance. The effect is devastating. One way to combat this emerging drug resistance problem is the development of novel drugs. However, cellular mechanisms of carboplatin-resistance are poorly understood. Without a thorough understanding of resistance mechanisms, developing long-lasting effective drugs for long term treatment is a challenging problem. Therefore, there is a dire need to develop methods to detect and study resistance mechanisms.

One suggested mechanism is the inhibition of drug uptake to prevent the intracellular accumulation of the drug. The presented work describes the quantification of carboplatin uptake in ovarian cancer cells. For this purpose, carboplatin is thoroughly characterized by voltammetry and its suitability for physiological bioelectrochemical studies is assessed. Diffusion and adsorption processes of carboplatin are evaluated, its dependence on pH is investigated, and a limit of detection for carboplatin at unmodified Pt electrodes is identified, without the need of expensive and time-intense electrode modification strategies. The influx and efflux of carboplatin into/from ovarian cancer cells are quantified by electrochemistry to better understand mechanisms of carboplatin chemoresistance. Results emerging from this research will be important for future medical research developing novel agents to combat chemoresistance and will present the basis for future long-term funding applications under this collaboration.

Reference:

Luu H.T.L., Nachtigal M.W., Kuss S.: Electrochemical Characterization of Carboplatin at Unmodified Platinum Electrodes and its Application to Drug Uptake Studies in Ovarian Cancer Cells. Journal of Electroanalytical Chemistry 2020, 872C, 114253.
Monitoring “Real-Time” Biological Binding Events on a Microelectrode Array
Authors: Zhu Yu , Moeller Kevin D
Published: July 2021

Because microelectrode arrays contain collections of spatially isolated electrodes that can each be individually addressed, they provide an intriguing platform for monitoring the activity of small molecules, peptides, and proteins. The arrays are utilized by placing the members of a molecular library on the surface of the array above the electrodes such that each unique member of the library is located on top of a unique electrode or a set of electrodes in the library. In this way, the binding activity on the molecular library and the electrochemical reactions happen on the electrodes are coupled. The binding events between the molecules on the surface of the array and molecules in solution can thus be monitored with the change of behavior of the electrochemical reactions on the electrodes. The overall strategy is illustrated in Figure below.

We are expanding the types of experiments that can be employed to examine enzyme-peptide binding with the use of microelectrode array. We have previously shown RGD-peptide/ integrin, v-107/ VEGF, and R6A - Gαi1 interactions can be monitored on an array. While success of the synthetic chemistry can be ensured by fluorescence labeling, the binding can be monitored by cyclic voltammogram.

Now, our focus has moved from distinguishing specific binding/non-specific binding/no binding to distinguishing different types of specific binding events. We are working to employ those electrochemical methods in conjunction with the traditional FRET studies in order to provide unique insights into the mechanism of peptide cleavage reactions. In so doing, we hope to add new capabilities to existing surface analytical methods.

Figure 1
Catalysis of Redox-Neutral Reactions By Electron Exchange between Electrodes and Organic Compounds
Authors: Roesel Arend , Broese Timo , Prudlik Adrian , Francke Robert
Published: July 2021

To most chemists the term ‘electrocatalysis’ is known as the facilitation of a heterogeneous electron transfer via a chemical interaction between the electrode and a substrate [1]. The opposite case, the utilization of a heterogeneous electron exchange to catalyze a chemical reaction (‘electrochemical catalysis’), is a much less known but yet a very powerful approach in electrosynthesis [2]. Here, the injection (or removal) of an electron into (or from) a substrate triggers a redox-neutral reaction (e.g. a molecular rearrangement) that may otherwise require harsh conditions and/or the use of reagents. Such processes involve the electrogeneration of an ionic or radical ionic species, which after a coupled chemical step either undergoes a backward electron exchange with the electrode (ECEb mechanism) or triggers a chain process in the bulk solution. Under these circumstances, sub-stoichiometric amounts of charge are sufficient to achieve a full conversion and conceptionally, the electrons and holes can be understood as being catalysts.

In this contribution, the concept of electrochemical catalysis will be illustrated using the Newman-Kwart rearrangement (NKR) of O-aryl thiocarbamates 2 to the corresponding S-aryl compounds 3 as an example (see scheme below) [3]. Generally, the NKR represents the key-reaction in the three-step synthesis of thiophenols 4 from phenols 1 and proceeds between 200 and 300 °C [3]. Electrochemical catalysis, however, allows for operation at room temperature and provides a complementary reactivity with respect to the arene substitution [3,4]. The results of batch and flow electrolysis will be presented, along with a detailed mechanistic analysis based on cyclic voltammetry studies, control experiments, and quantum chemical calculations.

References:

[1] R. Francke, B. Schille, M. Roemelt, Chem. Rev.
2018, 118, 4631.

[2] R. Francke, R. D. Little, ChemElectroChem.
2019, 6, 4373.

[3] T. Broese, A. F. Roesel, A. Prudlik, R. Francke, Org. Lett.
2018, 20, 7483.

[4] A. F. Roesel, M. Ugandi, N. T. T. Huyen, M. Majek, T. Broese, M. Roemelt, R. Francke, J. Org. Chem.
2020, 85, 8029.

Figure 1
(Organic and Biological Electrochemistry Division Manuel M. Baizer Award) Concepts for Electrifying Organic Synthesis
Authors: Waldvogel Siegfried R
Published: July 2021

The direct use of electrochemistry for the generation of reactive intermediates can have major advantages towards conventional synthetic strategies.[1] Less or no reagent waste is generated and new reaction pathways are accessible.[2] In order to exploit the electricity driven conversions for synthetic purposes and to install unique selectivity two modern approaches will be outlined:

Solvent-controlled selective dehydrogenative cross-coupling reactions: A key for this is the use of boron-doped diamond anodes and fluorinated alcohols within the electrolyte.[3] This methodology opened new pathways for innovative and scalable arylation reactions.[4]

New electrode systems for the anodic and cathodic conversion to value-added organic compounds. These systems are capable to go beyond common limits in electro-organic synthesis.

The working horse to identify suitable electrolytic conditions is the electrosynthetic screening approach. This strategy gives also rise to fast optimization and subsequent scale-up.[5]

References:

[1] E.J. Horn, B.R. Rosen, P.S. Baran, ACS Cent. Sci.
2 (2016) 302-307.

[2] a) S. Möhle, M. Zirbes, E. Rodrigo, T. Gieshoff, A. Wiebe, S. R. Waldvogel, Angew. Chem. Int. Ed. 57 (2018) 6018-6041; b) A. Wiebe, T. Gieshoff, S. Möhle, E. Rodrigo, M. Zirbes, S. R. Waldvogel, Angew. Chem. Int. Ed. 57 (2018) 5594-5619.

[3] L. Schulz, S.R. Waldvogel, Synlett 30 (2019) 275-286.

[4] S.R. Waldvogel, S. Lips, M. Selt, B. Riehl, C.J. Kampf, Chem.
Rev., 118 (2018) 6706-6765.

[5] C. Gütz, B. Klöckner, S.R. Waldvogel, Org. Process Res. Dev. 20 (2016) 26-32.
Understanding the Properties of Phenazine Mediators That Promote Extracellular Electron Transfer in Escherichia coli
Authors: Simoska Olja , Minteer Shelley D.
Published: July 2021

Establishing an efficient extracellular electron transfer (EET) between microorganisms and electrode surfaces plays a critical role in the development of mediated microbial electrochemical technologies. The two main EET mechanisms are (1) direct electron transfer (DET) from membrane-bound redox proteins and (2) indirect, mediated electron transfer (MET) via exogenous or endogenous electron shuttles (mediators). In DET, anodes are in physical contact with functional motifs (redox-active proteins) on the cellular surface, facilitating EET. However, most microbial-based systems do not have these redox surface proteins. Therefore, the use of artificial, redox-active mediator systems is necessary to facilitate and/or increase electron transfer. Here, we describe a phenazine-based mediator system to facilitate electron transfer from the model microbe Escherichia coli. Recognized for its extensive synthetic biology toolkit for bioelectrochemical purposes, E. coli offers various advantages, such as fast growth rates, easy culturing methods, and the ability to metabolize different substrates. However, detailed information on electron transfer mechanisms in E. coli with electrode surfaces and its interaction with redox mediators remain unclear. Phenazine redox mediators were experimentally evaluated, demonstrating distinct mediated current densities, dependent on the mediator structure. Our results show that the choice of a mediator with the appropriate redox potential is not the single aspect to consider in the rational design and development of future mediated EET systems.
Evaluating Organic Acids As Oxidizable Fuels in R. Capsulatus-Based Bioelectrochemical Systems
Authors: Beaver Kevin , Minteer Shelley D.
Published: July 2021

The development of microbial fuel cells (MFCs) for wastewater treatment has recently gained significant attention in the bioremediation and renewable energy industries. Bacteria can be integrated into the anodes of MFCs to oxidize organic wastes, simultaneously producing electrical current and decontaminating wastewater. The photoheterotrophic purple bacterium Rhodobacter capsulatus has demonstrated photo-catalyzed electron transfer to carbon electrodes via exogenous quinone redox mediators, and tolerance to high salinity, opening opportunities for solar-powered MFC systems for treatment of saline wastewater. While the consumption of malate by R. capsulatus has been electrochemically analyzed previously, in this project, alternative target carbon sources were examined in order to improve electrochemical performance of these R. capsulatus systems. A combination of electrochemical techniques and biological assays were used to evaluate the relative viability of malate, lactate, succinate and propionate as oxidizable fuels. Specifically, cyclic voltammetry and amperometry data demonstrated that R. capsulatus generates distinctive bio-photocurrent densities depending on the fuel metabolized. Bioanodes with immobilized R. capsulatus cells oxidizing lactate (9.49 ± 1.89 µA cm-2) as the fuel yielded the greatest mediated bio-photocurrent densities compared to the other fuels, while those metabolizing propionate (1.33 ± 0.18 µA cm-2) generated the smallest current densities. In tandem with electrochemistry methods, growth curve assays and RNA sequencing were performed to further delve into the biological effects of altering the carbon source.
Visualization of Mossy Zinc Electroplating Structure Evolution Via Operando Nanotomography
Authors: Wang Fan , Ge Mingyuan , Hitt Andrew , Xiao Xianghui , Guo Hua , Lee Wah-Keat , Savsatli Yavuz
Published: July 2021

Dendrite growth during electrodeposition is a critical challenge faced by high-energy metallic electrodes (e.g. Li, Zn) in rechargeable batteries. Under typical battery operation conditions, mossy structure forms on Li and Zn anode surface, which may be described as colonies of intertwined and branched filaments with diameters of ~ 100 nm. Compared to the well-known diffusion-limited dendritic growth, which occurs at much higher current density, the mossy growth process is vaguely described as “kinetically limited” in literature and its mechanism remains poorly understood. Recent study shows that the detachment of mossy filaments from substrate during electrostripping, which forms “dead lithium”, is a major cause of the battery capacity fading. A better understanding of the structure evolution of mossy deposits during cycling is therefore of considerable importance for developing successful strategies to improve the cycling life of metallic anodes.

In this study, we performed operando tomography of mossy zinc structure growth on Cu substrate during electrodeposition with nanoscale resolution at the National Synchrotron Light Source II. Zinc electroplating was carried out at a constant overpotential of 50mv in an in-situ electrodeposition cell made of a capillary tube with the working (Cu wire) and counter (Zn wire) electrodes inserted from opposite ends. Tomography datasets were collected every 2 minutes with an effective voxel size of 43 nm. The 3D structure of zinc deposits was reconstructed from the datasets using open-source code TomoPy.

Three different nucleation sites were observed, and the Zn mossy structure was divided into three groups according to these sites for a more detailed analysis. The calculated average porosity of the three mosses was ~35% and this was supported by ex-situ analysis. These three groups were separated into shells from their cores, and the most significant growth was occurring at the outermost shell. Further, the porosity and the volume of the inner shell and the core reached a steady state after a certain amount of time of electrodeposition. This result showed the penetration of the electrolyte to the inner parts of the mossy Zn was limited. All three mossy structure showed the same growth pattern without a preferred growth direction; however, there was an apparent difference of volume growth rate between them, indicating a possible diffusion limitation or uneven electric field distribution, which was in contrast with the previous studies. From ex-situ focus-ion beam scanning electron microscopy examination, it was shown that the moss structure was comprised of individual filaments, which repeatedly branched and entangled to form a mossy Zn.

Figure 1
Bio-Electrochemical Drug Metabolism and Inhibition: Underrated Liver Microsomal Bioelectrodes
Authors: Krishnan Sadagopan
Published: July 2021

From the initial attempts to deliver electrons to bulk microsomal solutions (1980s), and subsequent successful bioactive microsomal biofilm designs on electrodes (mid 2000s), the topic of bio-electrochemical cytochrome P450 has yielded commendable knowledge. Co-factor free, label-free, and stereoselective P450-specific metabolite production and isoform identification have immense potential for pharmaceutical drug development, metabolite profiling, and as a cost-effective complementing approach to tedious chemical synthesis, cell, and biological assays. In comparison to the progress on studying purified isolated electrocatalytic enzymes including cytochrome P450s, liver microsomal electrocatalysis is relatively a new topical area with many unknowns. Advancements and filling the knowledge gaps on the microsomal P450 electrocatalysis with nanomaterials and throughput designs hold the translational potential for practical usability by pharmaceutical industry. In this presentation, we share our contributions on various successful electro-interfacing of human liver microsomes with a range of electrode materials and nanomaterials for voltage-driven biocatalysis.
Alkyl S-Glycosides As Electroactive Glycosyl Donors: Study of the Effect of the Steric and Electronic Properties of the Aglycone and Protective Groups over the Oxidation Potential
Authors: Sanhueza Chavez Carlos , Deore Bhavesh Rajendra , Ocando Joseph
Published: July 2021

The oxidation potentials (E
ox) of a series of alkyl S-glycosides were determined using cyclic voltammetry and square-wave voltammetry. Model glycosides were designed to investigate the effect exerted by the steric and electronic properties of the alkyl aglycone and protective groups over the oxidation potentials. Glycosides substituted with small alkyl groups exhibited lower E
ox while compounds with bulky substituents presented peaks at more positive potentials. The results show a good correlation of E
ox with the volume of the aglycone substituent as well as with the calculated stability of the aglycone-derived thiyl radical. The effect of the protective groups on E
ox is, as expected, predominantly electronic. However, the increase of the protective group bulkiness leads to more positive peak potentials suggesting a steric contribution to E
ox modulation. The results of this study posse alkyl S-glycosides as convenient glycosyl donors for electrochemical glycosylations.
(Physical and Analytical Electrochemistry Division David C. Grahame Award) My 54 Years of Doing Electrochemistry and What Is New
Authors: Parkinson Bruce Alan
Published: July 2021

I am very honored to be selected to receive the David C. Graham Award from the Electrochemical Society, an award that has been bestowed on so many outstanding electrochemists over the years including many of my mentors. This symposium is also close to my 70th birthday and may then be near the end of attending ECS meetings. My talk will start with an acknowledgement that awards like this do not happen without the students, post docs and colleagues that have worked for me and with me over my 54 years of doing electrochemistry that started with science fairs in high school and is ending at the University of Wyoming. Ironically the first papers that I read when arriving in graduate school at Caltech were David Graham’s pioneering work on double layers at mercury electrodes that were very relevant to part of my PhD work on double layer effects on electron transfer kinetics at mercury electrodes. My post doc at Bell Labs introduced me to solid state science and semiconductor photoelectrochemistry as applied to solar energy conversion. These topics continued to interest me for the rest of my career in photoelectrochemistry but I was always interested in learning new things and attacking interesting problems and I will briefly review some of this work. These include research in the areas of UHV surface science, both developing and applying scanning probe microscopies, growth and applications of 2D materials (long before they became a trend) and even photoelectrochemical processes on the surface of Mars where we explained the photoelectrochemical origin of the high concentrations of perchlorate on the surface of Mars.

The rest of the talk will be concerned with an entirely new area for me, covalent organic framework (COF) materials applied to membranes applications, that has been a focus for the last few years. In this new project, a collaboration with colleagues at the University of Wyoming, involves developing two dimensional COFs with controllable sized hexagonal pores that we can functionalize with a wide variety of functional groups. We have been exploring applications of membranes constructed from these 2D-COFs for ion sieving based on size and charge, organic solvent separation and their antifouling abilities. Specifically, we have designed and tested a membrane constructed for a 2D-COF with pores that are lined with carboxylate groups that demonstrates a very specific size cut off for the conduction of a series of increasing sized tetraalkylammonium cations when paired with a polymeric anion that will not pass through the membrane. The stucture of this family of 2D-COFs is shown in the Figure. We have also demonstrated very high fluxes for organic solvent nanofiltration that is related to their polarity, size and hydrogen bonding properties. A future focus will be on developing a membrane that excludes small ions that will be useful in desalinization systems.

Figure 1