bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ion Transfer at Liquid | Liquid Interface Modified with Silica Nanoparticles
Authors: Collins Martha , Hernando-Abad Eduardo , Hébrant Marc , Herzog Gregoire 
Published: July 2021

The interface formed between two immiscible electrolyte solutions (ITIES) is a highly reproducible, defect-free surface that allows the assembly of nanometer-sized objects. Their adsorption at the liquid-liquid interface is governed by their dimensions, zeta potential, wettability and the interfacial tension. The interest for the use of silica nanomaterials at the ITIES is due to their favourable adsorption kinetics and to their rich surface chemistry that can provide selectivity.
At first, we followed the adsorption of silica nanoparticles (ø = 12 nm) at the ITIES by AC voltammetry and their interactions with methylene blue (MB+), selected as a model ion by cyclic voltammetry and UV-vis absorption spectroscopy. We determined the adsorption constant of the MB+ onto silica nanoparticles to be 1.66 × 105, which indicated a strong affinity between them. This is in contrast with two other ions tested (Eosin B and tetraethylammonium), which demonstrated low affinity for the silica nanoparticles.
In a second step, we synthesized silica nanoparticles with diclofenac molecular imprint with the aim of selective accumulation of diclofenac, a commonly used nonsteroidal anti-inflammatory drug. The presence of imprint cavities greatly improved the affinity for diclofenac for the silica nanoparticles, in contrast with diclofenac analogue such as aceclofenac. Electrochemistry experiments (including cyclic and AC voltammetries) revealed that diclofenac transfer is blocked by the presence of molecularly imprinted nanoparticles at the ITIES.
These two experimental examples show that target molecules can be accumulated at the ITIES by combining the ability of silica nanoparticles to adsorb onto the ITIES and their affinity for the targeted molecules. Such an accumulation localized at the interface could be of interest in sensing applications.

Figure 1
Earth-Abundant Electrocatalysts for the Oxygen Evolution Reaction of Water Splitting Using Nanostructured Layered Inorganic Materials
Authors: Colon Jorge L , Ramos-Garcés Mario V. , Sanchez Joel , Wu Yanyu , Barraza-Alvarez Isabel , La Luz-Rivera Kálery , Del Toro-Pedrosa Daniel E. , Villagran Dino , Jaramillo Thomas F 
Published: July 2021

Nature uses solar energy and earth-abundant materials for splitting water into oxygen, in the oxygen evolution reaction (OER), and protons, which are then reduced into hydrogen in the hydrogen evolution reaction (HER). Hydrogen solar fuel produced in artificial photosynthesis schemes for water splitting could be used in fuel cells. Learning from nature, instead of using expensive catalysts such as platinum, cheaper alternatives (such as cobalt, iron, or nickel) would provide the opportunity to make solar energy even more competitive with fossil fuels. However, obtaining efficient catalysts based on earth-abundant materials is still a daunting task, particularly for the OER. Recent theory has shown that nanoscopic confinement of catalysts increases the stability and efficiency of catalysts for OER. We have designed and develop earth-abundant electrocatalysts for oxygen reduction and water splitting using nanostructured layered inorganic materials of zirconium phosphate (ZrP). We have demonstrated improved electrocatalytic activity of ZrP nanomaterials loaded with metal ions suitable for the OER of water splitting. Adsorbing Co or Ni catalysts on the ZrP nanoparticles surface proved to improved OER activity compared to intercalated catalysts. A comparison between adsorbed Co or Ni catalysts and those catalysts on exfoliated ZrP hexagonal nanoplatelets proved that those on exfoliated nanoplatelets were more active, with diminished overpotentials and reduced Tafel plot slopes as well as higher mass activities. More recently, comparison between Co and Ni catalyst on ZrP particles with different morphologies (hexagonal platelets, rods, cubes, and spheres) revealed that the more active Co catalysts are those on hexagonal ZrP platelets, whereas the best Ni catalysts are those on ZrP spheres. Finally, encouraging recent results with a cobalt porphyrin catalyst will be presented, as well as recent XAS operando results. These results demonstrate that ZrP nanoparticles are suitable supports for electrocatalysis of the OER and water splitting.
Sponsored by NSF Center for Chemical Innovation in Solar Fuels CHE-1305124 and NSF-PREM Center for Interfacial Electrochemistry for Energy Materials (CIE2M) grant DMR-1827622.
Defective Metal-Organic Frameworks As Unpyrolyzed Electrocatalysts for Oxygen Reduction and Oxygen Evolution Reactions
Authors: Wang Hao 
Published: July 2021

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) represent core electrocatalytic processes in unitized regenerative fuel cells and rechargeable metal-air batteries catalyzed by the costly platinum group metals (PGMs) materials. Finding highly efficient yet durable ORR/OER catalysts using earth-abundant, low-cost materials represents a critical path in lowering cost barrier for widespread commercialization of the devices. We herein report two approaches to construct defective metal-organic frameworks (MOFs) to remove PGM usage for oxygen electrocatalysis.
In approach 1, we prepared a coordinately unsaturated Co-MOF as a bifunctional ORR/OER electrocatalyst in an alkaline electrolyte. The Co-MOF possessed great π-π stacking and hydrogen bonding interactions, giving rise to excellent structural and catalytic stabilities. Structure characterizations demonstrated that the coordination of Co(II) was largely unsaturated. Modeling simulations further confirmed that the unsaturated coordination significantly promoted the interactions with molecular water and oxygen and improved the electronic conductivity, leading to enhanced mass and charge transfer properties.
In approach 2, we developed a partial ligand removal (or ligand-defect) approach to create mesopores and unsaturated coordination in a Cu-MOF. Since the micropores typically limit the mass-transfer properties (and the capability to store insoluble discharge product for aprotic metal-air battery), the mesopores of the as-prepared MOF showed less steric hindrance, and the unsaturated Cu coordination also boosted electronic conductivity and auxiliary reactant affinity, leading to high Li-air battery capacity.
The defective MOFs may open up a new venue for developing effective electrocatalysts with enhanced intrinsic activity towards oxygen electrocatalysis.
Novel Synthesis of Manganese Single Atom Oxygen Reduction Reaction Catalyst for Enhanced Stability in Proton Exchange Membrane Fuel Cells
Authors: Stracensky Thomas , Yang Fan , Zhong Sichen , Jiao Li , Lattimer Judith , Jia Qingying , Mukerjee Sanjeev , Xu Hui 
Published: July 2021

In an effort to effectively implement proton exchange membrane fuel cells (PEMFCs) technology, there has been a drive for the development of platinum group metal free (PGM-free) oxygen reduction reaction (ORR) catalysts. To this end, iron based catalysts such as the single atom FeN4 catalyst have been identified as one of the most active species for the ORR in the PEMFCs . However, while initial activity of the catalyst is high, the stability of membrane and electrode assemblies (MEAs) is still poor upon extended operations. One degradation mechanism for Fe-based MEAs can be attributed to the Fenton reactions that produce highly reactive free radicals capable of attacking the FeN4 sites and membrane of the PEMFCs. Therefore, alternative catalysts that can mitigate Fenton reactions have been investigated to enhance the MEA stability in PEMFCs.
Manganese single atom-based catalyst is an attractive candidate to circumvent and mitigate the issue of radical formation and to provide a highly active and stable catalyst for the ORR in PEMFCs1. In this work we investigate the nature of the MnN4 site and develop a non-contact pyrolysis synthetic method to develop the MnN4 based catalyst. In this method CVD approach is used in conjunction with appropriate Mn precursor for deposition on nitrogen doped carbon (NC) to yield ORR active sites. The non-contact pyrolysis is a preferential method as it leads to minimal aggregation and forms active sites on the exterior of the catalyst particle with a high degree of accessibility for the oxygen reduction. The formation of MnN4 active sites was investigated using in-temperature X-ray absorption spectroscopy (XAS). The XAS results exemplified the need for high temperatures for MnN4 sites to form. This can be due to the competition between the competitive formation of Mn oxides and MnN4 sites that occurs during pyrolysis and higher temperatures favor the formation of the MnN4 sites. Additionally, electron paramagnetic resonance spectroscopy is used to further understand the nature of the Mn active sites and determine the effects of site oxidation on the ORR.
(1) Liu, K.; Qiao, Z.; Hwang, S.; Liu, Z.; Zhang, H.; Su, D.; Xu, H.; Wu, G.; Wang, G. Mn- and N- Doped Carbon as Promising Catalysts for Oxygen Reduction Reaction_ Theoretical Prediction and Experimental Validation. Applied Catalysis B: Environmental, (243) p. 195-203, 2019.
Voltammetry Combined with on-Line HPLC for the Electro-Oxidation of Formamidine Disulfide
Authors: Zhang Wei 
Published: July 2021

Formamidine disulfide is an important oxidation product of thiourea, the electro-oxidation mechanism is not well understood. Herein, the electro-oxidation of formamidine disulfide was studied by on-line HPLC combined with voltammetry. The sampling process on the electrode surface is controlled by a microporous sampler placed at the electrode interface while scanning, which allowed the electro-oxidation products to be detected at a given potential. The dependence of electrode product and electrode potential was determined, the main electro-oxidation products of formamidine disulfide are thiourea, formamidine sulfinic acid, cyanamide, and elemental sulfur.
In this study, We use on-line HPLC combined voltammetry to study the electro-oxidation of formamidine disulfide, the convective mass transfer control technique was applied to determine the electrode intermediates involved in the electrochemical reaction at a given potential. Similar to the RDE or RRDE technology, forced mass transfer control technology was introduced by sampling pump, but the direction of the mass transfer was rather different from the RDE or RRDE. The key of the forced mass transfer control technology is the rate control of the sampling pump. When the sampling rate of the pump is low, the mass transfer process on the electrode surface is not strong enough and the sampling too little affects the HPLC analysis, the excessive sampling rate of the pump has a great influence on the electrochemical voltammetry curve. A qualitative and quantitative analysis of electrode interface species can be carried out by on-line HPLC and electrochemical techniques, and the distribution of products with electric potential can be obtained more directly.
Combining voltammetry with on-line HPLC technique provided a effective approach for detecting the products on the surface of electrode formed at a given potential. In addition, when the intermediate products are produced on the electrode surface, sampling at the electrode interface causes a decrease in concentration, resulting in an increase in the peak current with the increase of the sampling speed. If the species in the solution reacts electrochemically, sampling near the electrode interface enhances the mass transfer process and the material in the bulk solution diffuses to the electrode surface faster, thus the peak current increases with the increase of the sampling speed, until reaching a plateau. Thus, as exemplified by the qualitative and quantitative analysis of the electro-oxidation products of TU2
2+, sampling using a microporous sampler on the platinum electrode surface allows in situ detection of the species and concentration changes on the electrode surface.

Figure 1
(Invited) Enhancement of Oxidation of Dimethyl Ether through Applicationof Metal-Oxide-Supported Noble Metal Catalytic Nanoparticles: Comparison to Behavior of Other Simple Organic Fuels
Authors: Rutkowska Iwona , Kulesza Pawel J. 
Published: July 2021

There has been growing interest in utilizing small (simple) organic molecules, as alternative fuels to hydrogen, in electrochemical energy conversion systems. In addition to ethanol (biofuel), that can be ideally oxidized to carbon dioxide thus delivering twelve electrons, recent important systems include dimethyl ether as well. But realistically the respective reaction is rather slow at ambient conditions. Obviously, there is a need to develop novel electrocatalytic materials.
Platinum has been recognized as the most active catalytic metal towards oxidation of ethanol at low and moderate temperatures. But Pt anodes are readily poisoned by the strongly adsorbed intermediates, namely by CO-type species, requiring fairly high overpotentials for their removal. To enhance activity of Pt catalysts towards methanol and ethanol oxidation, additional metals including ruthenium, tin, molybdenum, tungsten or rhodium are usually introduced as the alloying component. More recently it has been demonstrated that catalytic activity of platinum-based nanoparticles towards electrooxidation of ethanol has been significantly enhanced through interfacial modification with ultra-thin monolayer-type films of metal oxo species of tungsten, titanium or zirconium.
We pursue a concept of utilization of zirconia nad mixed metal (e.g. zirconium/tungsten or titanium/tungsten) oxide matrices for supporting and activating noble metal nanoparticles (e.g. PtRu) during electrooxidation of dimethyl ether relative to methanol, formic acid and ethanol. Among important issues is incorporation of additional metal (e.g. Rh or Pt) nanostructures capable of weakening, or even breaking, the C-C and C-O bonds in the ethanol and dimethyl ether molecules. On the other hand, rhodium itself is not directly electrocatalytic toward oxidation of ethanol. The oxides and noble metal nanoparticles have been deposited in a controlled manner using the layer-by-layer method. Remarkable increases of electrocatalytic currents measured under voltammetric and chronoamperometric conditions have been observed. The most likely explanation takes into account possibility of specific interactions of noble metals with transition metal oxide species as well as existence of active hydroxyl groups in the vicinity of catalytic noble metal sites. In addition, formation of “nanoreactors” where ethanol and dimethyl ether are partitioned (at Rh, Pt or Pd) to methanolic residues and further oxidized at PtRu cannot be excluded.
Surfactant-Free Preparation of Palladium Nanoparticles: Elucidation of Their Electrocatalytic Activity Toward Reduction of Carbon Dioxide
Authors: Wadas Anna , Kulesza Pawel J. 
Published: July 2021

The unique approach to fabrication of palladium nanoparticles by reduction of K2PdCl4 with ascorbic acid without the use of surfactants (such as polyvinylpyrrolidone) is proposed and adressed here. Capping agents and surfactants prevent agglomeration as well as make it possible to obtain nanoparticles in a narrow size range; on the other hand, their application results in the contamination of the Pd catalytic surfaces. In the present study, the resulting palladium nanoparticles have sizes on the level of 20-40 nm, and they are characterized by the presence of basic crystallographic planes such as (111) and (100). The results are supported with cyclic voltammetric studies, in addition to visualization and imaging with transmission electron microscopy and scanning electron microscopy.
Electrochemical reduction is very promising and relatively simple to apply and can be carried out at ambiemnt condition, and furthermore, its utility can be facilitated changing the electrolysis conditions (e.g., the reaction products can be selectively controlled). To evaluate the catalytic properties of Pd nanocubes and hexagonal phases fabricated here, they have been uniformly dispersed onto glassy carbon electrode, and the electrochemical reduction of CO2 have been considered as the electrocatalytic probe here. Controlled potential electrolysis of CO2 was then performed at different applied potentials in the CO2-saturated 0.1 M KHCO3 solution (pH 6.8). Electrochemical measurements indicate that application of the Pd-nanocube catalyst the electrochemical reduction of CO2 results in other reaction products when compared to the performance of the Pd hexagonal catalyst.
For comparison, the relationship between structural composition and electrochemical characteristics of palladium nanoparticles during the formic acid oxidation and the oxygen reduction reactions (in 0.5 M H2SO4) have also been considered here. The results are consistent with the view that the structural identity of palladium nanoparticles cannot be neglected during electrocatalystic studies and affects the systems’ overall performance.
(Invited) Chronoculometric Approach to Diagnosis of Oxygen Reduction at Low Pt-Content Electrocatalysts
Authors: Kulesza Pawel J. , Zdunek Kinga , Rutkowska Iwona , Negro Enrico , Vezzu Keti , Di Noto Vito 
Published: July 2021

Development of catalytic systems for oxygen reduction reaction is still one of the most issues with respect to potential applications in low-temperature fuel cells,. Considerable research efforts have centered on the development of Pt-free or low-Pt-content catalytic systems. The serious research has been focused on improving the catalytic activity of Pt-based catalysts in acid media with less Pt loading.
A useful mode for recording the electrochemical responses is to integrate the current and to report charge passed as a function of time. Chronocoulometry offers important advantages including good signal-to-noise ratio because the act of integration smooths random noise on the current transients. In comparison to chronoamperometry, by integrating the response, it is possible to separate surface phenomena more readily from bulk electrochemical responses. When it comes to the oxygen reduction, the double-potential-step chronocoulometry permits, in principle, estimation of the number of electrons (n) involved in the oxygen reduction and diagnosis of formation of the H2O2 intermediate. The problem lies in understanding the reaction kinetics and mechanisms in order to define properly experimental parameters.
The usefulness of the double-potential step chronocoulometric data in a form of the charge vs. square root of time plots is in the fast and reliable diagnosis of the mechanisms and dynamics of charge propagation. It is clearly apparent that, by proper adjustment of pulse times and other experimental parameters within the double-potential-step experiment, mechanistic considerations permitting estimation of the number of electrons involved and the percent of formation of the H2O2 intermediate are feasible. We demonstrate that not only Vulcan-supported platinum but also Pt nanoparticles dispersed over SiO2-derivatized reduced graphene oxide induce reduction of oxygen according to almost 4-electron mechanism.

Acknowledgements: This work was supported by the National Science Center (Poland) under Opus Project (2018/29/B/ST5/02627) and under auspices of the European Union EIT Raw Materials ALPE 19247 Project (Specific Grant Agreement No. EIT/RAW MATERIALS/SGA2020/1).
(Invited) ORR in Ca2+ Containing DMSO on Pt and Au Electrodes – Reaction Mechanism Studied By Dems, AFM and XPS and Varied Surface Structure
Authors: Koellisch-Mirbach Andreas , Park Inhee , Bawol Pawel Peter , Baltruschat Helmut 
Published: July 2021

Though Ca-O2 batteries show rising interest in the battery society due to their attractive energy density and availability of materials, the fundamental mechanisms of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in aprotic electrolytes are scarcely understood. This and preceding studies[1-3] aim at the investigation of the ORR mechanism especially on well-defined electrodes (single crystalline surfaces or those with adjusted roughness). Here we investigated the ORR in 0.1 M Ca(ClO4)2 in DMSO, as under convection for this system no deactivation is observed on Au and Pt electrodes. From earlier results[3, 4] we know, that on Au electrodes a slowly dissolving peroxide is formed, until a closed CaO2/CaO adsorbate layer is built up in a competing process, which inhibits further peroxide formation. The layer was characterized by XPS and AFM. An astonishing finding is that on Au electrodes of electrode roughness factor (fR) > 10 under convection, formation of superoxide is a diffusion limited process on top of the CaO2/CaO adsorbate layer (although peroxide formation is inhibited). In this study we also investigate the ORR/OER mechanism in the same system on Pt electrodes and compare the results to those, which we obtained from experiments on Au electrodes, as we found predominant superoxide formation on Pt electrodes in earlier studies[1]. This study shows, that also on Pt electrodes a CaO2/CaO adsorbate layer is the reason for predominant superoxide formation under convection. We found, that as one increases the electrode roughness, the ORR becomes more and more dominated by formation of adsorbed peroxide. Thus for low electrode roughness, we have to conclude that the in fact diffusion limited superoxide formation occurs through a CaO2/CaO adsorbate layer, which also on Pt electrodes inhibits further peroxide formation. As peroxide formation leads to almost complete electrode blocking in other M-O2 battery systems further leading to surface limited charges, one might think of utilizing the selective process inhibiting nature of the CaO2/CaO adsorbate layer to tackle those problems. Thus, in this study we will further show the influence of a CaO2/CaO adsorbate layer on Pt electrodes to the ORR in Li+ containing DMSO, as it is known, that Li2O2 effectively blocks the electrode.
[1] P. Reinsberg, C. J. Bondue, H. Baltruschat, Journal of Physical Chemistry C
2016, 120, 22179.
[2] P. Reinsberg, A. A. Abd-El-Latif, H. Baltruschat, Electrochimica Acta
2018, 273, 424.
[3] P. P. Bawol, P. H. Reinsberg, A. Koellisch-Mirbach, C. J. Bondue, H. Baltruschat, ChemRxiv (Preprint)
2020.
[4] A. Koellisch-Mirbach, I. Park, H. Baltruschat*, In preparation.