bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding Oxygen Anion Transport in Nb-Doped La0.7Sr0.3CoO3 Perovskite Materials
Authors: Dhongde Vicky , Basu Suddhasatwa , Haider Mohammad Ali
Published: July 2021

Simple perovskite structured electrode materials of the series (LaxSr1-xCoO3-
δ) are commonly utilised for high-temperature solid-state electrochemical cells and Li-air batteries with some limitations observed on prolong operations due to the structural instability associated with the segregation of strontium ions. In order to overcome this structural incompatibility, doping of heterovalent dopant at the B-site is proposed which could possibly improve upon the stability by controlling the segregation of surface cations. In addition, the doped structure is likely to provide faster oxygen anion transport through the vacancies in the structure, thereby improving its electrochemical performance. Herein, oxygen anion diffusion in pure La0.7Sr0.3CoO3--
δ (LSC) and Nb-doped La0.7Sr0.3Co0.95Nb0.05O3-
δ (LCSN) perovskite structure is calculated using molecular dynamics (MD) simulations. Self diffusion coefficient of oxygen ions in the LSCN structure is observed to increase by an order of magnitude (1.356×10-8 cm2/s) on Nb doping as compared to the undoped LSC structure (6.499×10-9 cm2/s) at 1073 K. On varying the Nb concentration from 0.05 to 0.15 and optimum Nb concentration is estimated to be 0.05 corresponding to a maximum oxygen anion diffusivity in the structure (1.356×10-8 cm2/s) at 1073 K.
Design and Mechanistic Understanding of Earth-Abundant Metal Chalcogenide Electrocatalysts for Selective Electrosynthesis of Hydrogen Peroxide
Authors: Sheng Hongyuan , Janes Aurora N , Schmidt J R , Jin Song
Published: July 2021

Hydrogen peroxide (H2O2) is a versatile and green oxidant with a variety of distributed applications such as environmental remediation, disinfection, and household sanitation, but its centralized chemical production via the anthraquinone process poses significant cost, energy, and safety concerns. Decentralized electrosynthesis using renewable electricity to selectively reduce O2 to H2O2 via the two-electron oxygen reduction reaction (2e- ORR) could better satisfy end-user demands on-site, yet robust, earth-abundant catalysts that are active and selective in acidic (or neutral) solutions are lacking. Here we present our recent joint efforts combining theory and experiments to establish rational design rules for selective and stable acidic 2e- ORR electrocatalysts based on earth-abundant metal chalcogenide compounds. We first showed that pyrite-type cobalt disulfide (CoS2) selectively catalyzes the acidic 2e- ORR at low overpotentials due to the spatial separation of active metal sites by anions, which kinetically suppresses the scission of O-O bond in OOH* adsorbate and the undesired 4e- ORR. We further established both pyrite- and marcasite-type cobalt diselenide (CoSe2) polymorphs as more stable and leaching-resistant acidic 2e- ORR catalysts because of the much weaker binding of O* adsorbate to Se sites. This stability allows for the bulk accumulation of practically useful 547 ppm H2O2 and the effective electro-Fenton degradation of organic pollutant for on-site environmental remediation. Building on the new mechanistic understanding, our ongoing developments and future perspectives of earth-abundant metal compound-based 2e- ORR electrocatalysts will also be discussed.
Atomically Dispersed Single Metal Site Catalysts for Oxygen Reduction in Acidic Media
Authors: Wu Gang
Published: July 2021

Proton exchange membrane fuel cells (PEMFCs) are leading candidates in utilizing clean energy resources for application in transportation, stationary, and portable devices. In PEMFCs, cathode catalysts are crucial for overall performance and durability due to kinetically slow oxygen reduction reactions (ORR). Because platinum (Pt), a state-of-the-art ORR catalyst, is rare and expensive, the development of high-performance platinum metal group (PGM)-free catalysts is highly desirable for future fuel cell technologies. Among various PGM-free catalyst formulations, metal and nitrogen co-doped carbon (M-N-C, M: Fe, Co, or Mn) catalysts have exhibited encouraging activity and stability in acidic media for the ORR, which possess great potential to replace Pt in the future. Therefore, based on our extensive experience in the field of ORR catalysis, the talk will comprehensively summarize the basic principles in the design and synthesis of M-N-C catalysts for durable, inexpensive, and high-performance PEMFCs with an emphasis on Co- and Mn-N-C catalysts to avoid Fenton reactions between Fe2+ and H2O2, which can generate free radicals and lead to the degradation of catalysts, ionomers, and membranes in PEMFCs. Furthermore, template-free 3D hydrocarbon frameworks as attractive precursors to advanced M-N-C catalysts will be discussed to enhance intrinsic ORR activities in acidic media significantly. Also, the long-term performance durability of M-N-C cathodes will be discussed extensively to provide potential solutions to enhance catalyst stability in PEMFCs. Finally, this talk will provide an overall perspective on the progress, challenges, and solutions of PGM-free catalysts for future PEMFC technologies.
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.
Synergy of Pt-Free Single Metal Sites for Promoting Pt and Pt3co Ordered Intermetallic Catalysts for Fuel Cells: Performance and Durability Improvements
Authors: Qiao Zhi , Li Chenzhao , Wang Chenyu , Xie Jian , Spendelow Jacob S. , Wu Gang
Published: July 2021

The reduction of platinum use and improvement of its catalytic performance has become the most critical steps to accelerate the development of proton-exchange membrane fuel cells (PEMFCs). Here we report a novel and facile method to boost the performance of the Pt-cased catalyst by integrating with an atomic platinum-group metal (PGM)–free active sites. Using iron-doped zeolitic imidazolate framework-8 (ZIF-8) derived carbon as support, we achieved a uniform deposition of Pt and intermetallic Pt-Co nanoparticles (NPs) through one-step synthesis, with average particle size 2.4 nm for Pt, 3.4 nm for L10 PtCo, and 4.2 nm for L12 Pt3Co. Besides, easy phase transfer during synthesis between ordered intermetallic structures L10 PtCo and L12 Pt3Co was achieved, and a comprehensive comparison between their catalytic performance was established. Synergistic catalysis between Pt or Pt-Co NPs over a PGM–free catalytic substrate derived from iron-doped ZIF-8 led to excellent oxygen reduction reaction (ORR) performance under both rotating disk electrode (RDE) and membrane electrode assembly (MEA) testing. Resulting pure Pt catalysts achieved ORR mass activities of 0.451 A/mgPt and retained 80% initial values after 30,000 voltage cycles in a fuel cell, superior to the DOE 2020 targets without using Pt alloy. Both PtCo and Pt3Co catalysts achieved better performance and exhibited all-sided excellence among mass activity, stability, and power density. Among them, Pt3Co reached the power density at 0.67 V of 923 mW/cm2 and retained 86% initial mass activity after 30,000 voltage cycles in a fuel cell. Their performance dependences on support material particle size and ionomer content were discussed and optimized in MEAs.
Molybdenum Sulfide and Mxene Based Electrocatalysts for Efficient Electrocatalytic Nitrogen Fixation
Authors: Tian Jian , Xu Xuesong , Chen Xiaoyue , Qian Xiu
Published: July 2021

Nitrogen fixation technologies to synthesize ammonia (NH3) from the atmospheric abundant N2 is a crucial chemical synthesis technique for the human production activities, because it is the main source of nitrogen for producing fertilizers, plastics, fibers, and explosives and so on. Among them, electrocatalytic NH3 synthesis is a promising strategy because it can convert water and N2 into NH3 using renewable solar energy, wind or hydro-driven electricity under ambient conditions. Herein, 1T/1Tˊ phase MoS2 and Ti3C2 MXene based NRR electrocatalysts are designed. They present outstanding ability and selectivity to NH3 and stability. We also investigate the nitrogen source of produced NH3 by 15N isotopic labeling test. Density functional theory calculations reveal the optimal reaction path of NRR with both associative distal and alternating pathways.

References:

Xuesong Xu, Xiujuan Tian, Benteng Sun, Zhangqian Liang, Hongzhi Cui, Jian Tian*, Minhua Shao,1T-phase molybdenum sulfide nanodots enable efficient electrocatalytic nitrogen fixation under ambient conditions, Applied Catalysis B: Environmental, 2020, 272, 118984.

2. Xuesong Xu, Benteng Sun, Zhangqian Liang, Hongzhi Cui, Jian Tian*, High-performance electrocatalytic conversion of N2 to NH3 using 1T-MoS2 anchored on Ti3C2 MXene under ambient conditions, ACS Applied Materials & Interfaces, 2020, 12, 26060-26067.
Electrocatalytic Reduction of Nitrogen Oxides By a Crystalline Carbon Nitride
Authors: Kulesa Krista , Baker Lane , Smith Jeremy
Published: July 2021

Of the trillions of tons of Haber-Bosch fertilizers generated annually for global consumption, only 17% contribute to human feedstock proteins. A large fraction of Haber-Bosch nitrogen is lost as hazardous oxidized waste (N
y
O
x
). Water-soluble NO3
– and NO2
– anions wash into aquatic ecosystems, where they feed dangerous algal blooms. The waste volatile N2O comprised nearly 7% of emissions in 2018, and has 300 times the global warming impact of CO2. Nature mediates N
y
O
x
redox through metalloheme chains aligned in enzymatic active sites. The poly(triazine imide) LiCl (PTI-LiCl) electrocatalyst mimics these heme chains through highly crystalline, layered carbon nitride nanosheets. PTI has advantages of both heterogeneous and homogeneous electrocatalysts: (i) PTI sequesters substrates as intercalants, (ii) PTI has high surface area with a known structure, and does not lose crystallinity upon introduction of abundant transition metals, (iii) PTI has an extended
π
system shuttles electrons to ordered active sites. PTI is active as a solid state electrocatalyst toward NO2
– reduction, with 31% Faradaic efficiency toward complete reduction to NH3. Approximately 50% of intrasheet Li+ can be exchanged with Cu2+ with no change to native crystallinity, suggesting an electrostatic interaction between PTI and Cu2+ single atoms. Remarkably, introducing Cu2+ improves the onset potential for electrocatalytic NO2
– reduction by nearly 0.5 V, and catalytic current increases by an order of magnitude. Since copper is also found at the active site in nitrous oxide reductase, CuPTI was investigated for electrocatalytic reduction of N2O. Preliminary results suggest CuPTI can electrochemically bind and reduce N2O.

Figure 1
Electrochemical Evaluation of Rhus Vernicifera Biocathodes for Oxygen Reduction Reaction in Neutral Media with Application in Air-Breathing Hybrid Microfluidic Fuel Cells
Authors: López-González Berenice , Zamora-Suárez Andrés , Cuevas-Muniz Francisco Mherande
Published: July 2021

In this work, a Rhus vernicifera laccase electrodes (RvL-Vulcan/Toray and RvL-ABTS-Vulcan/Toray) were prepared by adsorption method and evaluated toward oxygen reduction reaction by cyclic voltammetry. The characterization was complemented by FTIR with ATR, these results indicates the presence of bands corresponding to the presence of enzymatic material for both electrodes and ABTS in the RvL-ABTS-Vulcan/Toray. The biocathodes were evaluated in an air-breathing microfluidic fuel cell reported previously by our group. For these experiments, a hybrid air-breathing microfluidic fuel cell configuration was constructed by an Au-Vulcan/Toray anode and 5 mM Glucose/0.3 M KOH as anolyte and the RvL-Vulcan/Toray and RvL-ABTS-Vulcan/Toray as biocathodes and PBS 7 as catholyte solution. The results showed that the RvL-ABTS-Vulcan/Toray 16 mWcm-2 performance was better than RvL 3.4 mWcm-2. This result it is attributed to the presence of ABTS in the material inmobilized.
Enhancement of Oxygen Reduction Reaction Activity of Pt By Tuning Its D-band Center Via Transition Metal Oxide Support Interactions
Authors: Matsumoto Futoshi , Ando Fuma , Gunji Takao , Ohsaka Takeo , Abruna Hector
Published: July 2021

The enhancement of the oxygen reduction reaction (ORR) activity of platinum nanoparticles (Pt NPs) using transition metal oxide (MOx, M = Ti, Nb, Ta, W, Y and Zr) supports has been examined. In order to enable the use of transition metal oxides having low electric conductivity as supports, the Pt nanoparticles were formed on conducting cup-stacked carbon nanotubes (CSCNTs). Metal oxide composites (M1M2Ox) prepared from two types of transition metal (M1M2: TiNb, NbTa and TaW) precursors were also used as supports. Pt NPs were photodeposited on MOx/CSCNTs and M1M2Ox/CSCNTs supports, resulting in MOx/CSCNTs and M1M2Ox/CSCNTs-supported Pt NPs catalysts (abbreviated as Pt/MOx/CSCNTs and Pt/M1M2Ox/CSCNTs). Their ORR activities in 0.1 M HClO4 aqueous solution were found to significantly depend on the atomic ratio of M1 and M2 in M1M2Ox as well as the type of metal oxide support. A “volcano-type” dependence of the ORR activity (represented as current density, mass activity and specific activity at 0.9 V vs. RHE) on the Pt d-band center, relative to the Fermi level, was obtained in a series of the Pt/MOx/CSCNTs and Pt/M1M2Ox/CSCNTs catalysts. It was found that the d-band center values (ranging from -3.83 to -3.42 eV) of the Pt deposited on MOx/CSCNTs and M1M2Ox/CSCNTs supports were lower than that (-3.39 eV) of the reference Pt/carbon black (CB), and that the Pt/TiNbOx (Ti:Nb = 1:6.6 in atomic ratio)/CSCNTs with a d-band center of -3.59 eV exhibited the maximum ORR activity, in agreement with the theoretical expectation that an ORR catalyst having a d-band center which is ca. 0.2 eV lower than that of Pt would have maximal ORR activity. A possible contribution of lattice strain (geometric effect) to the enhanced ORR activity is also briefly discussed. Our results demonstrate that the ORR activity of Pt NPs deposited on a series of the metal oxide supports can be deliberately controlled by the choice of support and CSCNTs.
Metal Oxide Inclusion in Polycrystalline Platinum Nanoparticles for Ammonia Electrooxidation
Authors: Huertas Namir Andrea , Rivera-Ruiz Andrés D , Padin Jose , Cunci Lisandro
Published: July 2021

The interest in platinum nanoparticles has increased due to their unique properties for applications as catalysts. However, platinum is not available for large-scale applications because of its elevated price and limited resources. Thus, efforts to optimize a cost-effective electrocatalyst that can enhance the ammonia oxidation reaction are of special interest for alkaline fuel cell applications. In this work, we synthesized Pt nanoparticles by colloidal methods using different precursors (K2PtCl6 or H2Pt(OH)6) and alloying them with different metal oxides (Fe2O3 or CeO2) in order to compare their electrocatalytic activities for ammonia oxidation. A colloidal synthesis is a reaction in solution of a metal precursor with a reduction agent in the presence of a capping agent to form colloidal nanoparticles. The Pt- Fe2O3 and Pt-CeO2 alloys were prepared by sonicating the metal oxide in solvent solution for 60 minutes with Pt nanoparticles. The Pt alloys were mixed with Nafion to coat a glassy carbon electrode for the electrochemical characterization and to measure their electrocatalytic potential for ammonia oxidation. The electrocatalytic activities for ammonia oxidation was studied by cyclic voltammetry at a low scan rate (20 mV/s). No significant difference in the onset potential (average onset potential value is -0.460 V) for the ammonia oxidation is observed based on the metal precursor. The highest current density was achieved by nanoparticles synthesized from the H2Pt(OH)6 precursor, with a value of 27.4 x 10-2 mA/cm2 (K2PtCl6 precursor had a value of 25.8 x 10-2 mA/cm2). The addition of metal oxides was found to not significantly change the onset potential for ammonia oxidation. However, current densities decreased with the addition of both metal oxides. Current densities of nanoparticles synthesized from the H2Pt(OH)6 precursor decreased to 24.9 x 10-2 mA/cm2 with CeO2 addition, but increased to 28.2 x 10-2 mA/cm-2 when Fe2O3 was added. In contrast, current densities of nanoparticles synthesized from the K2PtCl6 precursor had no significant different with CeO2 addition (25.7 x 10-2 mA/cm-2) but reduced significantly with Fe2O3 addition (16.7 x 10-2 mA/cm-2). Further characterization techniques such as scanning electron microscopy and X-ray diffraction are currently being analyzed.
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.
(Invited) The Role of Structural Inhomogeneity in the Promotion of Electrochemical CO2 Conversion on Pristine and Doped Ligand-Protected Au Nanoparticle
Authors: Alfonso Dominic
Published: July 2021

The tremendous progress made in the first-principles mechanistic studies of the CO2 reduction process in ligand protected gold nanocluster and its various doped counterparts will be described. A significant finding is that the active form of the catalysts does not correspond to the fully ligand protected version because of the weak adsorption of relevant intermediates. Our calculations reveal that the reduction process is facilitated by a structurally inhomogeneous reaction center. Instead of an exposed metal center, it features a more thermodynamically favorable sulfur site which binds the intermediates in such a way that the process can occur at lower over-potentials. The results affirm the role of structural disorder in the surface region for this class of materials as a critical factor in the promotion of CO2 recycling under electrochemical environment. In the last segment, the application of an in-house micro-kinetic modeling code to analyze heterogeneously catalyzed electrochemical CO2 reduction process will be presented.
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.
Electrocatalytic and Protective Properties of Ruthenium-Derivatized Bacterial Biofilm on Electrodes and Photoelectrodes
Authors: Seta-Wiaderek Ewelina , Szaniawska Ewelina , Wagner Barbara , Frik Malgorzata , Rutkowska Iwona , Nieckarz Marta , Brzostek Katarzyna , Kulesza Pawel J.
Published: July 2021

Conversion of carbon dioxide is a process of particular scientific interest in recent years, due to the need to reduce the level of this greenhouse gas in the atmosphere by its storage and reduction. Another profit of the CO2 reduction is the possibility of producing useful chemical compounds from such a widespread in the environment source of carbon. Electrochemical and photoelectrochemical reduction of carbon dioxide are optional methods of obtaining fuel materials from CO2. However, because of the molecule stability and by that, high overpotentials of its electroreduction, and moreover because of the competitive hydrogen evolution reaction – efficient and selective catalytic systems active in the CO2 conversion process are sought.

There has been proposed a bioelectrocatalytic system for conversion of carbon dioxide, containing bacterial biofilm (of the species Yersinia enterocolitica) at the electrode surface. Biofilms are robust matrices, stable in a wide range of environmental conditions, able to operate at room temperature and under atmospheric pressure, and appear to be attractive for use in electrocatalytic processes. They easily create well developed three-dimensional structures on various types of surfaces, including diverse materials used in the construction of electrodes. Biofilms hydrated matrix allows the electrolyte ions to easily move at the electrocatalytic interface – as a result, biofilms resemble ion-conducting gel-type systems, supporting redox processes. The structure and properties of biofilms make it possible to immobilize catalytically active molecules in the microbial layer grown on the electrode surfaces, and therefore there has been proposed a catalytic system with the organometallic ruthenium (II) complex dispersed in the biological layer, active in the process of carbon dioxide conversion. Ruthenium (II) complex is immobilized in the biofilm matrix by successive modification of the liquid medium (Luria-Bertani medium) for culturing bacteria with a solution of this complex compound. In addition, a biological matrix is used (along with the ruthenium (II) complex molecules dispersed in its layer) as a protective coating, stabilizing the unstable p-type semiconductor – copper (I) oxide. The proposed catalytic system present activity in the photoelectrochemical reduction of carbon dioxide and stability under experimental conditions.
Chemically Robust Metal–Organic Framework-Based Materials for Electroanalysis and Energy Storage
Authors: Kung Chung-Wei
Published: July 2021

Given several advantages of metal–organic frameworks (MOFs) including regular porosity, ultrahigh specific surface area, and periodic intra-framework functionality [1], MOFs have been considered as desirable thin-film materials deposited on electrode surfaces for various electrochemical applications including electrocatalysis, electroanalysis, and energy storage [2]. However, the electrically insulating nature and relatively poor chemical stability of most MOFs strongly limit their use in these applications [2-3].

In this presentation, various strategies that render the use of MOF-based thin films for electrochemical sensors and energy storage will be highlighted. The talk will cover several recent examples demonstrated by our research group that can facilitate the use of such porous thin films for electrochemical applications, such as: (1) the synthesis of chemically stable MOFs facilitating charge transport for electroanalysis [4-6], (2) the design of conductive MOF-based nanocomposites for supercapacitors [7], and (3) the pore-confined active species in MOF thin films that can exhibit remarkable electrochemical activity [8-9]. With rational material designs mentioned above, MOF thin films can be considered as advanced platforms for a range of electrochemical applications.

References:

[1] H. Furukawa, K.E. Cordova, M. O’Keeffe, O.M. Yaghi, Science 341 (2013) 1230444.

[2] J.H. Li, Y.S. Wang, Y.C. Chen, C.W. Kung, Appl. Sci. 9 (2019) 2427.

[3] C.W. Kung, S. Goswami, I. Hod, T.C. Wang, J. Duan, O.K. Farha, J.T. Hupp, Acc. Chem. Res. 53 (2020) 1187-1195.

[4] Y.C. Chen, W.H. Chiang, D. Kurniawan, P.C. Yeh, K. Otake, C.W. Kung, ACS Appl. Mater. Interfaces 11 (2019) 35319-35326.

[5] C.H. Chuang, J.H. Li, Y.C. Chen, Y.S. Wang, C.W. Kung, J. Phys. Chem. C 124 (2020) 20854-20863.

[6] W.H. Ho, T.Y. Chen, K. Otake, Y.C. Chen, Y.S. Wang, J.H. Li, H.Y. Chen, C.W. Kung, Chem. Commun. 56 (2020) 11763-11766.

[7] Y.S. Wang, J.L. Liao, Y.S. Li, Y.C. Chen, J.H. Li, W.H. Ho, W.H. Chiang, C.W. Kung, ACS Appl. Nano Mater. 3 (2020) 1448-1456.

[8] Y.S. Chang, J.H. Li, Y.C. Chen, W.H. Ho, Y.D. Song, C.W. Kung, Electrochim. Acta 347 (2020) 136276.

[9] J.H. Li, Y.C. Chen, Y.S. Wang, W.H. Ho, Y.J. Gu, C.H. Chuang, Y.D. Song, C.W. Kung, ACS Appl. Energy Mater. 3 (2020) 6258-6267.

Figure 1
Light Capture and Energy Conversion in Plasmonic-Polymeric Hybrid Nanoelectrodes
Authors: Searles Emily K. , Collins Sean S.E. , Tauzin Lawrence J. , Link Stephan , Landes Christy F.
Published: July 2021

Plasmonic nanomaterials have absorption cross-sections exceeding other classes of materials but dephase quickly into their dielectric environment. In this work, plasmonic-polymeric nanoantenna-reactor systems are hybridized to increase the electron-hole pair lifetime through interfacial redistribution. The electron-hole pair can then be extracted to drive catalysis as the selected polymeric acceptor, a metallophthalocyanine, has been shown to catalysis O2 and CO2 reduction efficiently. Single particle spectroelectrochemistry was used to characterize the energy transfer efficiencies of the hybrid structures by recording the surface plasmon resonance energy linewidth change during in situ polymerization. The electrochemical polymerization is selective and photoenhanced on the surface of the gold nanorods. We complement resonance energy transfer efficiencies calculated from single particle changes in linewidth with calculations from excitation polarization-dependent photoluminescence measurements. Non-radiative energy transfer efficiencies up to 50% are achieved for plasmonic-polymeric nano-antenna reactors. The understanding of interfacial transfer pathways between plasmonic-polymeric materials will lead to control and tunability of scalable hybrid nanoelectrodes.
RoDSE Electro-Assembling of Iron Quantum Dots on Vulcan Xc-72R for ORR Toward Peroxide Generation for Space Applications
Authors: Pena-Duarte Armando , Hayes Kathleen , Vijapur Santosh Hanamant , Hall Timothy , Taylor E. Jennings , Del Pilar Joselyn , Cabrera Carlos
Published: July 2021

Highly dispersed iron-based quantum dots onto powdered Vulcan XC-72R substrate were successfully electrodeposited by the rotating disk slurry (RoDSE) technique. Our findings through chemical physics characterization revealed that the continuous electron pathway interaction between the interface metal-carbon is controlled. The RDE, RRDE, and PGU of in-situ H2O2 generation in fuel cell experiments revealed a high activity for the oxygen reduction reaction (ORR) via two-electron pathway. These results establish the Fe/Vulcan catalyst at a competitive level for space and terrestrial new materials carriers, specifically for the in-situ H2O2 production. Transmission electron microscopy (TEM) analysis reveals the well-dispersed Fe-based quantum dots with a particle size of 4 nm. The structural and chemical-physical characterization through ICP, TEM, STEM, HAADF-STEM, XRD, Raman spectroscopy, XPS, XANES, and EXAFs; reveals that, under atmospheric conditions, our quantum dots system is a Fe2+/3+/Fe3+ combination. The QDs oxidation state tunability was showed by the applied potential. The obtention of H2O2 under the compatibility conditions of the drinking water resources available in the International Space Station (ISS) enhances the applicability of this iron- and carbon-based materials for in-situ H2O2 production in future space scenarios. Terrestrial and space abundance of iron and carbon, combined with its low toxicity and high stability, consolidates this present work to be further extended for the large-scale production of Fe-based nanoparticles for several applications.
(Invited) Anodic TiO2 Nanotube Layers: Efficient Photocatalyst
Authors: Macak Jan M. , Sopha Hanna , Motola Martin , Zazpe Raul , Rodriguez Pereira Jhonatan
Published: July 2021

The self-organized TiO2 nanotube layers have attracted considerable scientific and technological interest over the past 15 years motivated by their possible range of applications including photocatalysis, solar cells, hydrogen generation and biomedical uses [1,2]. The synthesis of these 1D TiO2 nanotube layers is carried out by a conventional electrochemical anodization of valve Ti metal sheet.

Among other TiO2 nanomaterials, these nanotube layers stand out due to their directionality, tunability of dimensions, ability to absorb significant amount of incident light and the possibility to utilize nanotube interiors and exteriors for decoration-coating of secondary materials.

One of the most significant applications of TiO2 nanomaterials is photocatalysis, which is very effective to decompose various pollutants (e.g. dyes) and kill bacteria [3,4].

The presentation will focus on the utilization of the nanotube layer for photocatalytic removal of various species in the liquid phase [5, 6] as well as gas phase [7]. We will demonstrate the photocatalytic performance of recently developed single-wall TiO2 nanotubes and single-tube TiO2 powders [8]. We will also show that various modifications of nanotube ssecondary materials have a positive influence on photo-electrochemical properties of nanotube layers [9,10]. Experimental details and some recent photocatalytic results will be presented and discussed.

References:

[1] J. M. Macak et al., Curr.
Opin. Solid State Mater.
Sci.,
2007, 1-2, 3.

[2] K. Lee et al., Chem. Rev., 2014, 114, 9385.

[3] K. Rajeshwar et al., J. Photochem. Photobiol. C: Photochem. Rev.
2008, 9, 171.

[4] Ch. Wei et al., Environ.Sci. Technol.
1994, 28, 934.

[5] J.M. Macak et al., Small, 2007, 3, 300.

[6] H. Sopha et al., Appl. Mater. Today,
2017, 9, 104.

[7] H. Sopha et al., Electrochem. Commun.,
2018, 97, 91.

[8] D. Beketova et al., ACS Appl. Nano Mater. 2020, 3, 1553

[9] F. Dvorak et al., Appl. Mater. Today,
2019, 14, 1.

[10] M. Motola et al, Nanoscale, 2019, 11, 23126.
(Invited) N-Doped Carbon-Based Materials: Improved Fundamental Understanding through Comprehensive Characterization
Authors: Pylypenko Svitlana
Published: July 2021

N-doped carbon materials are used across a wide range of energy applications including fuel cell catalysts, CO2 electroreduction, catalyst supports, and energy storage materials. They are often integrated with metals in the form of either metal nanoparticles or atomically-dispersed sites to tune their performance for specific catalytic reactions. In general, these materials are very heterogeneous, containing a multitude of nitrogen functionalities and therefore, they are intrinsically challenging to understand, requiring a wide range of characterization techniques.

This talk will discuss a family of N-doped catalysts derived from a series of N-doped carbon nanospheres. N-doped nanospheres, produced solvothermally, are synthesized with the ability to control size, shape, concentration of nitrogen dopants, and their nitrogen functionalities. The tunability of these spheres allows for systematic studies that help to identify trends with different N functionalities and densities. Platinum and non-platinum metals were incorporated using various synthetic routes, targeting formation of either metal nanoparticles or atomically-dispersed species. Understanding the surface and bulk chemistry of these materials is essential for elucidating the effects of nitrogen dopants on nucleation and stability of metals across the periodic table. Trends observed experimentally will be compared with metal adsorption computations with the goal of extending beyond experimental data to make predictions for more efficient catalyst development. Within a catalyst layer, the surface chemistry also affects interactions with ionomer, and both the nature of the metal and its morphology, as well as the functionality of nitrogen impacts these interactions.