bluuebunny/crossref_metadata_2025 huggingface dataset:
Hetero-Bimetallic Paddlewheel Complexes for Enhanced CO2 Reduction Selectivity: A First Principles Study
Authors: McCarver Gavin , Yildirim Taner , Zhou Wei
Published: August 2024

The reduction of carbon dioxide (CO2) into value-added feedstock materials, fine chemicals, and fuels represents a crucial approach for meeting contemporary chemical demands while reducing dependence on petrochemical sources. Optimizing catalysts for the CO2 reduction reaction can entail employing first principles methods to identify catalysts possessing desirable attributes, including the ability to form diverse products, selectively form few products, or exhibit favorable reaction kinetics. In this study, we investigate the CO2 reduction reaction on bimetallic Cu paddlewheel complexes, aiming to understand the impact metal substitution with Mn, Co, or Ni has on bimetallic paddlewheel metal-organic frameworks (MOFs). Substituting one of the Cu sites of the paddlewheel complex with Mn results in a more catalytically active Cu center, poised to produce substantial quantities of formic acid (HCOOH) and minor quantities of methane (CH4) with a suppressed production of C2 products such as ethanol (CH3CH2OH) or ethylene (C2H4). Moreover, the presence of Mn significantly reduces the limiting potential for CO2 reduction from 2.22 eV on the homo-bimetallic Cu paddlewheel complex to 1.19 eV, thereby necessitating a smaller applied potential. Conversely, within the Co-substituted paddlewheel complex, the Co site emerges as the primary catalytic center, selectively yielding CH4 as the sole reduced CO2 product, with a limiting potential of 1.22 eV. Notably, the Co site faces substantial competition from H2 production, attributed to a lower limiting potential of 0.81 eV for hydrogen reduction. Our examination of the Cu-Ni paddlewheel complex, featuring a Ni substituent site, reveals two catalytically active centers, each promoting distinct reductive processes. Both the Ni and Cu sites exhibit a propensity for HCOOH formation, with the Ni site favoring further reduction to CH4, while the Cu site directs the reaction towards methanol (CH3OH) production. The significance of this study lies in its potential to inform and streamline future experimental efforts, facilitating the synthesis and evaluation of novel catalysts with superior capabilities for CO2 reduction.
Key Factors for Electrochemical Carbon Dioxide Reduction at Ni-N-C Catalysts
Authors: Ko Youngdon , Osmieri Luigi , Zhang Hanguang , Zelenay Piotr
Published: August 2024

Electrochemical carbon dioxide reduction reaction (CO2RR) has the potential to adequately contribute to addressing the energy and environmental challenges faced by the humanity today. The surplus of CO2 produced by burning fossil fuels can be transformed into valuable products by CO2RR. An effective use of this approach on a large scale requires active, selective, and stable CO2 reduction electrocatalysts. Additionally, insightful understanding of interfacial behavior such as water wetting and carbonate formation at the electrode is required to enhance the performance and durability of CO2RR electrocatalysts.1 Atomically dispersed Ni-N-C materials have attracted attention due to their superior selectivity for CO generation.2 Their activity and selectivity of CO2RR are influenced by the metal center and local atomic defects in M-N-C catalysts.3 In addition to catalyst structures, electrode composition and structure have also substantial impact on the activity and selectivity of CO2RR. Particularly, ionomer compositions and the electrode fabrication process can alter the hydrophobicity of the electrode and the local pH on the catalyst, resulting in considerable changes in CO2RR activity and selectivity.

In this presentation, we will report on the performance of various electrodes fabricated with the Ni-N-C catalyst, using different types of ionomers and measured in a flow cell and zero-gap electrolyzer at > 100 mA/cm2 current densities for CO2RR. We will also introduce an approach that aims at reducing carbonate formation at the CO2RR electrolyzer cathode by the modifications to the electrolyte composition, the CO2 inlet humidity, and the electrochemical cell temperature.

Acknowledgement

Research presented in this work was supported by the Laboratory Directed Research and Development program of Los Alamos National Laboratory under project number 20230065DR.

References

(1) Sa, Y. J.; Lee, C. W.; Lee, S. Y.; Na, J.; Lee, U.; Hwang, Y. J. Catalyst–electrolyte interface chemistry for electrochemical CO2 reduction. Chemical Society Reviews
2020, 49 (18), 6632-6665.

(2) Wu, J.; Sharifi, T.; Gao, Y.; Zhang, T.; Ajayan, P. M. Emerging Carbon-Based Heterogeneous Catalysts for Electrochemical Reduction of Carbon Dioxide into Value-Added Chemicals. Advanced Materials
2019, 31 (13), 1804257.

(3) Liang, S.; Huang, L.; Gao, Y.; Wang, Q.; Liu, B. Electrochemical Reduction of CO2 to CO over Transition Metal/N-Doped Carbon Catalysts: The Active Sites and Reaction Mechanism. Advanced Science
2021, 8 (24), 2102886.
(Invited) Elucidating the Cation Effect in CO2 Electroreduction Using Non-Metal Cations
Authors: Feng Xiaofeng
Published: August 2024

Electrochemical reduction of CO2 may enable a promising route for the recycling of CO2 and the sustainable production of chemicals and fuels. Due to the complex electrochemical environment, a deeper understanding of the reaction mechanism, particularly the role of cations in the process, is still needed. It was recently demonstrated that metal cations are essential for the CO2 reduction to CO, by stabilizing the CO2
– intermediate via electrostatic interaction. Here we investigate the cation effect in CO2 reduction using non-metal cations, particularly quaternary ammonium cations, whose size and shape symmetry can be tuned. We select CO2 reduction on Bi catalyst that produces both CO and formate, thus to reveal and compare the effect of cations on the two reaction pathways. Interestingly, the Faradaic efficiency for CO production increased apparently for the electrolyte with larger cations, while the formate Faradaic efficiency showed a weak dependence on the cation size, indicating a reaction-pathway-dependent effect of the cations. We further compared cations with different symmetries and observed a more profound effect of substituted ammonium cations on the CO2 reduction activity and selectivity, which was attributed to the charge distribution and weak hydration shells of the cations that help stabilize reaction intermediates. Our work elucidates the critical role of cations in the CO2 electroreduction catalysis and suggests a method to improve the electrocatalysis with optimized electrolytes.
Carbonate Electrolysis for Energy Efficient Direct Air Capture of CO2
Authors: Tong Emily , Kastelic Matthew , McCatty Steve , Lattimer Judith
Published: August 2024

Yearly global energy related CO2 emissions continue to increase, reaching a record breaking 37 billion metric tons in 2022. As a major greenhouse gas, CO2 levels need to be reduced by 10s of gigatons to prevent the worst of climate change, something that is no longer feasible with net-zero emissions alone. Removing atmospheric CO2 is therefore of critical importance for the future of our planet. While major improvements have been made in CO2 capture from large point sources, a significant portion of CO2 emitted each year from the United States comes from distributed sources such as cars and smaller factories. Due to the dilute concentrations of CO2 in ambient air, Direct Air Capture (DAC) needs to be highly selective to preferentially absorb CO2 to collect useable amounts. These challenges have made current DAC systems quite costly, both energetically and economically, and require vastly different strategies than carbon capture from concentrated sources.

At Giner, we are developing a novel process for the capture and regeneration of CO2 from air into a purified, concentrated CO2 stream that can be redirected as a feedstock for a wide range of applications, including chemical manufacturing and syngas formation. This process involves the capture of CO2 in a concentrated KOH solution using a high-surface area air contactor to form potassium carbonate. The potassium carbonate is then efficiently electrolyzed in a hydrogen-assisted process to regenerate the CO2 at a low operating potential, increasing the electrical efficiency of the process while producing concentrated and purified CO2. In addition, water, hydrogen, and KOH are also regenerated as byproducts that can be recycled back into the CO2 capture and electrolysis processes, reducing both overall energy and chemical consumption.

Giner has developed a unique 3-compartment carbonate electrolysis flow cell. Using our electrolyzer, we have seen operating voltage as low as 1.2 V at 100 mA/cm2 in a 5 cm2 cell for potassium carbonate conversion to CO2 with H2 assisted electrolysis. Significant improvements in operating voltage have come from optimization of gas-diffusion layers (GDLs), cell geometry, and membrane selection. Furthermore, we have achieved >97% pure CO2 formation in the internal flow-through compartment. Currently, scale-up is in progress to apply these developments to approach comparable conditions in a 50 cm2 multi-cell stack. Further developments will enable pairing with an in-house, carbonate based, air contactor allowing for capture and regeneration of over 1 ton CO2
per year.

Acknowledgement: The project is financially supported by the Department of Energy's ARPA-E Office under the Grant DE-AR0001495
The Impact of Nife-Based Metal Alloy on CO2 Conversion to CH4 and Carboxylic Acids in a Microbial Electrosynthesis Cell
Authors: Nwanebu Emmanuel , Tartakovsky Boris , Tanguay-Rioux Fabrice , Gharbi Rihab , Omanovic Sasha
Published: August 2024

The goal of this study was to evaluate the impact of NiFe-based metal alloys on the CO2 conversion to carboxylic acids and methane (CH4) in CO2-fed Microbial Electrosynthesis (MES) cells. First, the impact of transition metal alloys on CO2 conversion and product specificity was studied in a MES cell with a conductive polymer cathode with electrodeposited NiFeBi alloy. It was found that the presence of the NiFeBi alloy significantly decreased production of CH4 from 0.5 to 0.1 L (Lc d) – 1, suggesting that methanogenic activity was suppressed in the presence of NiFeBi. On the other hand, the production of carboxylic acids consisting mainly of acetate, propionate and butyrate increased. Specifically, acetate production, which represented 80% of the total carboxylic acids in the cathode liquid increased by 70% to 1.0 g(Lc d)-1. This initial study demonstrated that product selectivity can be influenced by electrodeposition of transition metal alloys such as NiFeBi. It might be preferable to achieve selective production of high value long chain carboxylic acids such as valerate and caproate instead of acetate.

Accordingly, in the following experiments NiFeMn and NiFeSn alloys were electrodeposited on carbon felt cathodes and evaluated for enhanced CO2 conversion in MES cells. Both alloys enhanced CH4 production, which reached 0.8 L (Lc d)-1. However, there was no observable improvement in acetate production (0.2 – 0.5 g (Lc d)-1) or other higher chain carboxylic acids in comparison to NiFeBi – coated MES. It was suggested that by using a more biocompatible carbon-based support for alloy electrodeposition, it is possible to improve acetate, butyrate and caproate production. In addition, it is important to facilitate nutrient transport through the three-dimensional (3D) cathode. Limited transport of CO2, H2 and nutrients was identified as a potential rate-limiting factor when using carbon felt electrode. 3D-printed conductive polymer lattices were manufactured and electrodeposited with NiFeSn and NiFeMn alloys. The NiFeMn-coated lattice showed insignificant improvement in higher chain carbon production, however caproate concentration was increased five folds on NiFeSn-coated cathode. Also, electrochemical characterization demonstrated increased hydrogen evolution reaction rate over time. Nevertheless, the throughput of this product remained low at 0.1 g (Lc d)-1).

These results indicate that the presence of the NiFe-based metal alloys significantly influenced the electron transfer efficiency from the cathodes to microbial electroactive biofilms leading to increased formation of carboxylic acids in the cathode liquid. Therefore, the next step is to design more efficient 3D conductive polymer lattice electrodeposited with NiFeSn metal alloy to increase CO2 conversion to longer chain carboxylic acids.
The Best of Both Worlds: Stacked Catalytic Layers for the Electrocatalytic Generation of CO in Zero-Gap Electrolyzers
Authors: Pellumbi Kevinjeorjios , Hoof Lucas , Blaudzsun Dennis , junge Puring Kai , Apfel Ulf-Peter
Published: August 2024

Tailoring the properties of the catalytic layer (CL) alongside its architecture is a key development towards ensuring both improve efficiency and selectivity for CO2 electrolyzers. Traditionally, CLs for the CO2R consist of a single binder-material or a combination of them overtaking both the ion-conductance and maintenance of a hydrophobic environment.

We herein decoupled these processes into two individual, stacked catalyst-containing layers. Specifically, a hydrophobic catalytic layer was herein placed on the GDL aiming to improve water management within the CL during CO2R in zero-gap electrolyzers, while A second catalytic layer bound by an ion-conducting binder allows for the conduction of OH- and HCO3-/CO3
2- during CO2R, improving both the ionic conductivity between the GDE and AEM as well as the mechanical adhesion between the different interfaces. Notably, we present the complete stepwise CL-optimization pathway, regarding both the single and segmented-CLs towards the CO2-CO conversion at current densities ≥ 300 mA cm2, highlighting the role of the operational parameters regarding scalability in different cell sizes and long-term stability > 100 h.
Electrochemical Hydrogen Pump Using CsH2PO4/SnO2 Composite Proton Conducting Membrane
Authors: Gupta Minal , Zhang Kangkang , Huang Kevin
Published: August 2024

Liquid organic hydrogen carriers (LOHCs) are molecular compounds that have potential to be a promising class of hydrogen storage materials. Upon thermal treatment and in the presence of catalysts, H2-rich LOHCs can give off H2 without phase change. One immediate example is methylcyclohexane (C7H14) (MCH) conversion to toluene (C7H8) (TOL). The rate of H2 production of LOHC’s dehydrogenation reaction is kinetically limited. Therefore, adequate catalysts can help boost kinetics. An alternative approach to overcome the kinetic limitation is to shift the dehydrogenation reaction by removing H2 in the product via either a chemical or electrochemical route. Here we show an electrochemical H2 pump concept to promote the dehydrogenation reaction of MCH to TOL by pumping out H2 from the product line. We selected the super-protonic conductor CsH2PO4 (CDP) as the electrolyte for the pump due to the operating temperature of the dehydrogenation reaction (250-350 oC). However, CDP would not be stable if there is an insufficient amount of H2O (<38%) in the working environment, irreversibly dehydrated into a low-conductivity phase. On the other hand, too much H2O in MCH stream would negatively affect the catalytic performance of MCH-to-TOL conversion. Therefore, it is critical to limit the H2O content in MCH stream without affecting H2 pump performance.

Here, we report the use of SnO2 to stabilize the super-protonic conducting phase in CDP. SnO2 is a super-hydrophilic material. We first show the ionic conductivity stabilization over a broad H2O content to demonstrate the effectiveness of SnO2 in stabilizing CDP conductivity. We then show the performance of H2 pump based on the composite CDP-SnO2 protonic conductor. We also show materials characterization results including XRD, SEM and Raman to facilitate our understanding of the observed improvement and degradation. Overall, this study provides a supporting method to accelerate the production of green hydrogen with LOHCs.
Diagnosing Copper-Palladium Bimetallic Cathode Capability in CO2 Electrolyzers through Surface Enhanced Raman Spectroscopy
Authors: Yao Koffi P.C. , Mishra Mritunjay
Published: August 2024

The electrochemical reduction of CO2 offers potential for utilizing CO2 as a carbon feedstock and storing intermittent renewable energy. Presently, copper stands out as the only electrocatalyst capable of reducing CO2 into multiple hydrocarbon products. However, the performance of Cu catalysts is hindered due to poor selectivity, stability and high overpotential. In addressing these bottlenecks, our research focuses on the synthesis and characterization of Pd doped Cu bimetallic catalysts, for improving the selectivity and stability of Cu catalysts during CO2 reduction. We leverage cutting-edge In-situ Shell-Isolated Nanoparticles Enhanced Raman Spectroscopy (SHINERS) to investigate structural and compositional changes on the catalyst surface during electrochemical processes within a CO2 electrolyzer. Our preliminary in-situ Raman findings indicate a strong link between the selectivity of the bimetallic electrocatalyst in CO2 electrolysis and the surface oxide phases of the catalysts. This investigation provides crucial insights for designing an efficient electrocatalyst for CO2 reduction.
A and B Site Doped Barium Niobates with Improved Electrical Properties of Electrochemical Oxidative Coupling of Methane
Authors: Ramaiyan Kannan , Grosso Samuel , Denoyer Luke H , Benavidez Angelica , Garzon Fernando H.
Published: August 2024

Electrochemical oxidative coupling of methane (E-OCM) to produce ethylene is gaining renewed interest due the ability to control the conversion rate and product selectivity though temperature and applied potential. We previously demonstrate Mg, Fe and Ca, Fe codoped barium niobates have remarkable methane activation properties coupled with good chemical stability. Nevertheless, their electrical conductivity remained less than 50 mScm-1 that is low for electrode application. Hence, we attempted both A and B site doping on barium niobates with various dopants such as Sr, La (A site), and Ca, Mg, Fe, Co, Ni, Y (B site) to improve their electrical properties. These doped niobates showed enhanced thermochemical stability in SOFC relevant conditions and catalytic activity towards methane activation. The redox behavior of the Nb4+/5+ couple seem to be at a key reason behind this redox stability while the size and electronegativity of the dopants affect the electrical properties. The chemical stability was analyzed by TGA measurements followed by analysis of the perovskite powders using PXRD measurements. Impedance measurements under difference gas environments were utilized to analyze their electrical conductivity. Chronoamperometric measurements were utilized to evaluate the E-OCM properties of these catalysts. Our results demonstrate doped barium niobates as a promising candidate for stable operation in high temperature electrochemical applications.

References

H. Denoyer, A. Benavidez, A. Brearley, K. P. Ramaiyan*, F. H. Garzon*, “Electrochemical oxidative coupling of methane: deciphering the exceptional properties of BaMg0.33Nb0.67-xFexO3-δ for enhanced electrocatalysis and durable operation” Under revision J. Electrochem. Soc, (December 2023).

H. Denoyer, A. Benavidez, F. H. Garzon*, K. P. Ramaiyan*, “Highly Stable Doped Barium Niobate Based Electrocatalysts for Effective Electrochemical Coupling of Methane to Ethylene” Adv. Mater. Interfaces,
2022, 2200796 (1-9).

Ramaiyan, L. H. Denoyer, A. Benavidez, F. H. Garzon*, “Role of Dopants in Fine-Tuning the Electrical and Catalytic Properties of Barium Niobate Perovskites Towards High-Temperature Electrolyzer Application” ECS Transactions 2023, 111, 1139.

H. Denoyer, A. Benavidez, A. Brearley, K. Ramaiyan, F. H. Garzon*, “Chemical Stability of BaMg0.33Nb0.67-XFexO3-δ in High Temperature Methane Conversion Environments” ECS Transactions, 2023, 111, 587.
Protonic Ceramic Electrochemical Cell Manufacturing at Idaho National Laboratory
Authors: Zhao Zeyu , Wu Wei , Zhang Yuchen , Tong Jianhua , Ding Dong
Published: August 2024

Protonic Ceramic Electrochemical Cells (PCECs), operating at intermediate temperatures of 400-600oC, show great potential for hydrogen production and versatile chemical manufacturing. As this technology rapidly evolves, scaling up production in both quantity and size is crucial. This step bridges the gap between fundamental academic research on small button cells (e.g., 10 mm to 1 inch) and higher-technology readiness level development of industry-standard units (> 10x10 cm2) for stack assembly. At Idaho National Laboratory, we've made significant strides in this transition by applying advanced manufacturing technologies and our expertise in materials science and engineering. Our approach integrates materials, structural, and interface engineering research and development into the cell fabrication process, guided by a stringent quality assurance and quality control (QA&QC) system. This ensures the reliable, repeatable, and durable performance of PCECs.
(Invited) Advancement in Electrosynthesis of Fuels and Chemicals Using H2O and/or CO2 and N2 at Intermediate Temperatures at Idaho National Laboratory
Authors: Ding Dong
Published: August 2024

Fuels and commodity chemicals make up a significant share of the potential energy savings opportunities for decarbonized economy and society. New innovative technologies are needed that can reduce the amount of energy and carbon intensity currently required to produce the key fuels and chemicals or associated building blocks. Electrochemistry is playing an increasingly important role in manufacturing as we reduce energy use and address uncertain supply chains driven by industrial electrification. In comparison to processes driven by heat and pressure, electrochemically driven synthesis of fuels and chemicals provides unique opportunities for selective reactions and separations offering increased flexibility to manufacturing. As one of DOE’s premier multi-program energy research laboratories, Idaho National Laboratory’s (INL) mission is to ensure the nation’s energy security with safe, competitive and sustainable energy systems and unique national and homeland security capabilities. INL’s initiative, integrated energy systems (IES) provides carbon-free nuclear and renewable energy for downstream use in manufacturing and transportation. The manufacturing component of IES focuses on integrating clean, carbon-free electrons with waste/renewable heat and includes both manufacturing of electrochemical devices and implementing them in energy-efficient processes. In this talk, we will provide representative examples for the pillar of energy to molecules and materials (E2M2) by utilizing the protonic ceramic electrochemical cells/membrane reactors (PCEC/PCEMR). The electrochemical route using PCEC/PCEMR offers a solution of process intensification and low carbon intensity. We will also share our cost perspective when compared to other lower and higher temperature counterparts.
Enhanced Electrochemical Performance of Double Perovskites as Cathodes in Reversible Ceramic Electrochemical Cells through Nb Doping
Authors: Li Qingyuan , Li Wenyuan , Liu Xingbo
Published: August 2024

Efficient and cost-effective generation of electricity and hydrogen holds promise through reversible protonic ceramic electrochemical cells (R-PCECs). However, the successful commercialization of R-PCECs depends on the advancement of air electrodes that are both highly active and durable. Here, we made an air electrode material with two phases of double perovskite and single perovskite by doping Nb into B-site of the traditional PrBaCo2O6 double perovskite. The coexistence of the mixed double perovskite and single perovskite phases demonstrates superior electrochemical performance and durability compared to pristine double perovskite and single perovskite materials when employed as cathode materials. X-ray photoelectron spectroscopy (XPS), synchrotron radiation X-ray absorption spectroscopy (XAS) and neutron diffraction analysis reveal that this enhancement is primarily attributed to the introduction of high-valence Nb5+, resulting in an increased number of oxygen vacancies and structural stability. The findings presented in this study contribute valuable insights into the design and development of advanced cathode materials for solid oxide fuel cells and electrolyzers, with the potential for applications in sustainable energy conversion and storage technologies.
The Effects of Pressure on Lithium Alloying/Dealloying
Authors: Wang Congcheng , McDowell Matthew Todd
Published: August 2024

Stack pressure and mechanical confinement play important roles in influencing electro-chemo-mechanical phenomena of active materials in batteries, fuel cells, electrolyzers, and other energy conversion/storage devices. Despite progress in engineering strategies that aim to achieve stable stress/strain evolution and durable device performance, our mechanistic understanding of the coupling between mechanics and electrochemistry that govern structural evolution and electrochemical behavior of electrodes remains limited. Here, we investigate the effects of stack pressure on electrochemical lithium (de)alloying using both liquid and solid-state electrolytes. We elucidate the role of stack pressure on morphological evolution and electrochemical behavior of various alloy anodes in lithium batteries. Based on the understanding gained herein, we design an interfacial layer for alloy anodes in solid-state batteries to achieve high capacity and stable cycling at low stack pressures. These results provide insight into the phase transformation mechanism of metals and alloys under mechanical confinement, and they have implications for the development of high-energy solid-state battery systems.
(Invited) Adsorbate Coverage Steers Selectivity during Catalytic Nitrate Reduction
Authors: Senftle Thomas Patrick , Chen Yu
Published: August 2024

Nitrate (NO3
-) is a pervasive contaminant in groundwater that is harmful to human health. In this talk, we will discuss strategies for developing (electro)catalysts that selectively reduce NO3
- to either dinitrogen (N2), which is the desirable product if the goal is to remove NO3
- from drinking water, or to ammonia (NH3), which is the desirable produce for resource recovery. Using density functional theory (DFT), we found that product selectivity to NH3 versus N2 is controlled by competition between N-H bond formation and N-N bond formation on Cu and Pd surfaces. On the Cu(100) surface, N-H bond formation is favorable in the hydrogenation step of surface-bound NO*. This leads to the formation of an HNO* intermediate that is readily reduced to NH3. On the Pd(100) surface, NO* is hydrogenated to form an NOH* intermediate that is readily reduced to N*. N2 then is generated through a N*-NO* coupling step. Importantly, we found that the N-N bond formation barrier on Pd is highly dependent on the NO* surface coverage, where a high NO* coverage lowers the N*-NO* coupling barrier. As such, increased NO* coverage enhances N2 selectivity. Using this concept, we worked with collaborators to design a Pd nanocube electrocatalyst with partial Cu coverage that achieves high NO3
- reduction activity and N2 selectivity by increasing NO* coverage through a Cu-to-Pd spillover mechanism (ACS Catal. 2023, 13, 1, 87–98). This work highlights the importance of NO* surface coverage for controlling product selectivity, explains the different selectivity observed for Cu and Pd, and demonstrates strategies for boosting N2 selectivity through NO* spillover.
Electrochemical Approaches for Enhanced Phosphorus Recovery from Synthetic Animal Wastewater: A Comparative Analysis of Response Surface Methodology and Artificial Neural Networks
Authors: Ojoawo Babatunde IBRAHIM , Trembly Jason , Daramola Damilola
Published: August 2024

Electrochemical recovery from animal wastewater is a novel and comprehensive strategy needed in the effort to develop sustainable technology and nutrient delivery solutions, with an emphasis on nitrogen (N) and phosphorus (P) components. This research study addresses critical global environmental sustainability challenges associated with waste by contributing to the evolving conversation on nutrient recovery by using synthetic animal wastewater (SAW) as a substrate. This approach presents a viable solution for wastewater treatment and aligns with the sustainable management of water and energy resources.

This research utilized a Box-Behnken experimental design framework formulated with the aid of Minitab Statistical Software. The constructed design laid out a series of experimental runs (comprising 12 distinct conditions, each replicated twice, along with five central points) to explore the influence of three different variables (Mg:Ca molar ratio, N:P molar ratio, and temperature), each at three distinct levels, on phosphorus removal efficiency. The relationship between these three variables and the removal efficiency was then investigated using two distinct modeling methods: Artificial Neural Networks (ANN) and Response Surface Methodology (RSM). ANN, part of machine learning, involves developing a model that learns from experimental data using a network of neurons for training and validation. This allows the ANN to address complex, nonlinear relationships between variables effectively. Conversely, based on statistical analysis, RSM focused on understanding the interactions between the multiple factors, using designed experiments to build a model. Employing both methods leveraged ANN's prowess in handling nonlinearity and RSM's strength in experimental design and optimization, offering a comprehensive approach to enhance P removal efficiency from SAW. The combination of these approaches provided a deep insight into the dynamics of the process, aiding in the effective optimization of the removal response.

However, at optimal conditions, the ANN model predicted a higher P removal efficiency (66%) than RSM (45%). The precision of the ANN predictions was reflected in the minimal error margins with Root Mean Squared Error (RMSE) of 2.4, suggesting the robustness of this model in predicting the optimal conditions for P removal compared to the RSM, with an RMSE of 4.7. These findings underscore the potential of employing ANN and RSM to enhance the phosphorus removal process in wastewater treatment applications and show how ANN gives better predictions than RSM. Additional details will be presented at the meeting, including experimental data, regression models, and neural networks.
Pt/C and PtRu/C Catalysts Prepared by Modified Sulfite Complex Routes for Fuel Cell Applications
Authors: Lo Vecchio Carmelo , Mosca Erminia , Dollenz Riccardo , Mondello Angelo , Baglio Vincenzo
Published: August 2024

In-house 30 wt.% Pt and 50 wt.% Pt1Ru1 catalysts supported on high-surface area carbon (Ketjenblack, abbreviated as KB) were synthesized by the sulfite complex route. Two different procedures involving either a direct mixing of Pt-sulfite and Ru-sulfite complexes or Pt-sulfite preparation and subsequent impregnation of Ru precursor were adopted for the bimetallic species. In both cases, an impregnation of the formed metal oxides onto KB was adopted to increase the electronic conductivity of the samples. Finally, a carbothermal treatment at 600°C in He atmosphere was carried out for the reduction of the metal oxides to metallic PtRu/C compounds. The Pt1Ru1 ratio was calculated and revealed by X-ray fluorescence (XRF) analysis whereas the carbon percentage was calculated by weight loss. 50 mg of sample was treated in air at 550°C for 2 h and, after cooling, the weight corresponded to 25 mg, confirming a carbonaceous matrix percentage of 50 wt.%. In a similar way, the 30 wt.% Pt/C was determined. X-ray diffraction (XRD) revealed that the samples showed face centered cubic (fcc) structure for Pt nanoparticles. It appears that two distinct crystallographic phases of Pt and Ru nanoparticles were encountered after the synthesis conducted by Ru impregnation. In contrast, only a single fcc phase is visible when the Pt and Ru sulfite precursors were mixed, confirming the formation of an alloy. Furthermore, Scanning Transmission Electron Microscopy-Energy dispersive X-ray spectroscopy (S/TEM-EDX) and X-ray Photoelectron Spectroscopy (XPS) were used to characterize the differences in morphology and surface characteristics of the catalysts.

For the electrochemical measurements, rotating disc electrode (RDE) technique under acid and alkaline conditions was employed to investigate the half cell reactions. The catalysts were also deposited at the anode and cathode of fuel cells to evaluate the activity, performance, and short-term durability.

Acknowledgement

“This research was funded by the European Union – EIT Raw Materials in the framework of the following project: LYDIA- Recycling Critical Metals from Fuel Cells (G.A. 22019)”
Nanoparticles for Active and Sustainable Fuel Cell Cathodes
Authors: Kazimova Nargiz , Romero Nuria , Cavaliere Sara , Cavarroc Marjorie , Philippot Karine
Published: August 2024

Depletion of fossil fuels and environmental pollution raised interest in new technologies for sustainable energy production, conversion, and storage, among which fuel cell technology is greatly studied, in both academia and industry. Proton exchange membrane fuel cells (PEMFCs) are reputed energy devices, due to their high conversion efficiency and low environmental pollution.1 Nowadays, Pt-based catalysts exhibit the best electrocatalytic activity towards oxygen reduction reaction (ORR), but enhancing their catalytic efficiency and reducing costs are essential for commercializing fuel cell technology.2

Our interest relies with the development of Pt-based nanoalloys2,4 via solution organometallic chemistry approach.3 This approach allows control over the composition, structure, and morphology of metal nanoparticles, and could lead to increased catalytic activity and long-term stability by revealing more active sites of the catalyst. Additionally, the ability to alloy with a range of metals for producing bimetallic compounds is one of the key advantages of this approach.

In this communication, the synthesis of Pt-based nanoparticles and their characterization by state-of-the-art techniques such as ICP, EA, IR, TEM and HR-TEM will be described. The influence of the Pt complexes used as precursors and of the reaction conditions on the morphology of the Pt nanoparticles will be shown. The obtained nanostructures offer interesting starting materials to incorporate other metals, such as transition or rare earth metals, in order to have nanoalloys and study their performance in ORR in comparison to pure Pt catalysts.

References

[1] X. Tang, D. Fang, L. Qu, D. Xu, X. Qin, B. Qin, W. Song, Z. Shao, B. Yi, Chin. J. Catal. 2019, 40, 504–514.

[2] X. Ren, Q. Lv, L. Liu, B. Liu, Y. Wang, A. Liu, G. Wu, Sustain. Energy Fuels 2019, 4, 15–30.

[3] C. Amiens, B. Chaudret, D. Ciuculescu-Pradines, V. Collière, K. Fajerwerg, P. Fau, M. Kahn, A. Maisonnat, K. Soulantica, K. Philippot, New J. Chem. 2013, 37, 3374–3401.

[4] J. Greeley, I.E.L Stephens, A. S Bondarenko, T. P. Johansson, H.A. Hansen, T. F Jaramillo, J. Rossmeisl, I. Chorkendorff, J.K. Nørskov, Nat. Chem. 2009, 1, 552–556.
Investigation of the Optimal Phosphine for Improved Electrochemical Peptide Synthesis
Authors: Shinjo Shingo , Okada Yohei , Hiratsuka Goki , Kitano Yoshikazu , Chiba Kazuhiro
Published: August 2024

Peptides have been expected to be medicines with higher specificity and fewer side effects than conventional medicines. However, a longstanding problem that the huge amount of waste is produced in synthetic process is not resolved. One of the causes is use of coupling reagents. Although they facilitate efficient peptide bond formation, byproducts lead to accumulation of waste. To address the issue, we developed electrochemical peptide synthesis using triphenylphosphine (Ph3P) as a coupling reagent. Anodic oxidation of Ph3P generates radical cation to activate carboxylic acids and promote peptide bond formation, producing triphenylphosphine oxide (Ph3PO). Since the reduction of Ph3PO to Ph3P is achieved in various ways, Ph3P have a potential to be a recyclable coupling reagent, which would be one of the solutions. Actually, we succeeded in development of an electrochemical peptide synthesis applicable to all of canonical amino acids and recovering method of Ph3PO. Nevertheless, we found that this method is difficult to use for highly sterically hindered amino acids. To improve the reaction efficiency, we examined various phosphine derivatives instead of Ph3P. We will present our recent improvement of the electrochemical peptide synthesis and nature of phosphine radical cations in detail.
Electropolymerization of Various Aromatic Monomers Using Streaming Potentials
Authors: Iwai Suguru , Sato Kosuke , Hasegawa George , Ishizuka Norio , Matsukawa Kimihiro , Tomita Ikuyoshi , Inagi Shinsuke
Published: August 2024

Bipolar electrodes, i.e., wireless electrodes driven by an external electric field, have been paying more and more attention1. Electrolysis using bipolar electrodes is an eco-friendly electrolysis system because they work with a low concentration of supporting electrolytes, which become waste after reactions. Indeed, we achieved the electrochemical fluorination on the bipolar electrodes, reducing the amount of supporting electrolyte to 1/100 compared to a conventional electrolysis2. However, in bipolar electrolysis, driving electrodes are necessary to generate an external electric field, which creates concern regarding the side reaction occurring on the driving electrode. Streaming potentials can be promising candidates to solve this problem. Streaming potentials are the potential differences between an inlet and an outlet of a narrow channel, which is generated when low-concentrated electrolytes are fed into the channel3. In the previous work, we developed a bipolar electrode system using the streaming potential4. The streaming potential was successfully generated by filling the cotton into a narrow channel to conduct the electropolymerization of pyrrole and 3,4-ethylenedioxythiophene. Yet, a large pressure drop of about 10 MPa is needed in this case. Moreover, the value of streaming potential is still low and the monomer scope was limited to pyrrole and 3,4-ethylenedioxythiophene.

In this study, we aimed to investigate the condition with a low-pressure drop and a high-streaming potential, which enabled to expand the scope of electropolymerization. The screening of the filling declared that a polymer monolith, a porous material having continuous pores, was the best filling material for electrolysis. Then, the electropolymerization of thiophene and the ruthenium monomer, which could not be polymerized with the cotton-filled channel because of a low-streaming potential, was successfully carried out to obtain the corresponding polymers. The details of the streaming potential measurement and electropolymerization will be presented in the talk.

References

N. Shida, Y. Zhou, S. Inagi, Acc. Chem. Res., 2019,52, 2598–2608.

K. Miyamoto, H. Nishiyama, I. Tomita, S. Inagi, ChemElectroChem, 2019, 6, 97–100.

A. V. Delgado, F. González-Caballero, R. J. Hunter, L. K. Koopal, J. Lyklema, J. Colloid Interface. Sci., 2007, 309, 194–224.

S. Iwai, T. Suzuki, H. Sakagami, K. Miyamoto, Z. Chen, M. Konishi, E. Villani, N. Shida, I. Tomita, S. Inagi, Commun. Chem., 2022, 5, 66.

Figure 1
Magnetic Metalloimmunoassays: Influence of Particle Shape and Size on Galvanic Exchange-Based Electrochemical Detection
Authors: Walgama Charuksha , Adrian Daniel , Cardenas Marco , Bui Trang
Published: August 2024

The electrooxidation of silver (Ag) offers improved signal sharpness and intensity, enabling precise measurements and enhanced resolution in electrochemical sensing. Leveraging silver nanoparticles (AgNPs) as indirect labels in electrochemical assays provides a distinct advantage for detecting various biomarkers at clinically relevant concentrations. In our recent work, we have introduced an electrochemical approach that involves a galvanic exchange (GE) reaction between electrodeposited gold and AgNPs, followed by anodic stripping voltammetry (ASV), with potential applications in immunosensing. In this assay protocol, specific monoclonal antibodies immobilize the biomarker of interest separately on AgNPs and magnetic beads. Subsequently, magnetic bead-AgNP conjugates are attracted to the electrode surface by a magnetic force. However, to achieve the expected analytical performance of the bioassay, it is imperative to characterize the composition, size, shape, and surface modifications of the AgNPs. Consequently, our research focuses on investigating the electrochemical properties of a model bioconjugate formed between magnetic microbeads (MB) and AgNPs through Streptavidin-biotin interactions under various assay conditions. Notably, our recent studies reveal that conducting the GE cycle for three repetitions significantly enhances the Ag signal, yielding an improvement of approximately two-fold or greater compared to previously reported methods. Previous studies have shown that altering the shape of AgNPs, transitioning from nanospheres to other forms like nanocubes and nanodisks enhances both the limit of detection and the range of analyte detection. However, despite these enhancements, spherical AgNPs remain the most stable and easily synthesized option, characterized by excellent homogeneity. Recently, we compared AgNPs with diameters ranging from 20 to 100 nm paired with magnetic microbeads with diameters spanning from 50 nm to 3 µm to identify the optimal combination. Preliminary results indicate that the Mb (3 µm)-AgNP (50 nm) conjugate exhibits the highest Ag charge and Ag collection efficiency. Nonetheless, critical knowledge gaps persist regarding the fundamental understanding of the electrogenerated GE process and we are continually working on refining the electrochemical and assay parameters to develop a robust universal platform for GE-based electrochemical immunosensing.
Cytochrome c Oxidase Detection in Human Fibroblasts Using Scanning Electrochemical Microscopy
Authors: Thind Shubhneet , Lima Dhésmon , Booy Evan , Trinh Dao , McKenna Sean , Kuss Sabine
Published: August 2024

Cytochrome C Oxidase Deficiency (COXD) is a disorder caused by the mutation in genes encoding for the cytochrome c oxidase enzyme (COX),1 a mitochondrial multimeric enzyme which acts as the terminal electron acceptor in the electron transport chain.2 COXD causes serious health issues in affected individuals, including severe muscle weakness, brain damage and disorders in organs such as heart, liver and kidneys.1 Diagnosis is mostly performed by muscle biopsy,3,4 which is invasive and time-consuming. Finding new effective and early diagnostic strategies is therefore crucial to minimize symptoms and long-term disabilities. This research proposes the use of scanning electrochemical microscopy (SECM) as a promising method to quantify COX activity in normal and COXD fibroblasts as cell models. We explore the interaction of the redox probe N,N,N’,N’-tetramethyl-p-phenylene diamine (TMPD) with COX as an indicator of enzymatic activity.5,6 A platinum ultramicroelectrode was used to monitor electrochemical currents at different scan speeds, which were later used to determine an apparent heterogeneous rate constant (k
0) for TMPD regeneration by each cell line using numerical modelling. A significant difference in k
0 values (p < 0.1) was observed when comparing normal and COXD fibroblasts. The further treatment of normal fibroblasts with a COX inhibitor, NaN3,7 induced significant decreases in k
0 (p < 0.01). The COX activity results determined using SECM were in good agreement with a standard spectrophotometric assay. Taken together, our findings confirm SECM as an effective and rapid method to detect COXD in living tissues and provides a foundation for the development of new assays to diagnose COXD in infants.

References

M. Brischigliaro and M. Zeviani, Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1862, 148335 (2021).

A. Timón-Gómez et al., Semin Cell Dev Biol, 76, 163–178 (2018).

M. L. Simard, A. Mourier, L. C. Greaves, R. W. Taylor, and J. B. Stewart, Journal of Pathology, 245, 311–323 (2018).

S. B. Wortmann, J. A. Mayr, J. M. Nuoffer, H. Prokisch, and W. Sperl, Neuropediatrics, 48, 309–314 (2017).

S. Kuss, E. E. L. Tanner, M. Ordovas-Montanes, and R. G. Compton, Chem Sci, 8, 7682–7688 (2017).

S. Thind et al., Proc Natl Acad Sci U S A (2023). In press.

M. J. Fei et al., Acta Crystallogr D Biol Crystallogr, 56, 529–535 (2000).
(Invited) Understanding the Nano-Biointerface to Improve Biorecognition in Electrochemical Biosensing
Authors: Cardoso Costa Clara , Silveira Toldo Gustavo , Cancino-Bernardi Juliana
Published: August 2024

Nano-biointerface knowledge inspire both diagnostic and therapeutic functions in the nanomedicine area with remarkable progress. Biomimicking nanoparticles with cell membranes are one of the most innovative approaches to enhance performance, selectivity, and functionality for biomedical applications1,2. The cell membrane coating provides several advantages such as enhanced biocompatibility, improved stability, and specific targeting capabilities due to inherit properties of the source cells3. These advantages can be transferred to the biosensing scenario. For examples, to improve the specificity and selectivity of SARS-CoV-2 biosensors, the angiotensin-converting enzyme 2 (ACE-2) transmembrane receptor, that are overexpressed in respiratory model cells, was used as biorecognition element. In this new SARS-CoV-2 detection platform, cellular membranes from VeroCCL81 (mVero) and Calu-3 (mCalu) cells (which overexpress the ACE-2 transmembrane receptors) were extracted and immobilized as vesicles on an indium tin oxide electrode (ITO). Electrochemical impedance spectroscopy was used to optimize the performance of the developed devices for SARS-CoV-2 detection. The membrane biosensors showed limit of detection of 10.0 pg/mL and 7.25 pg/mL and limit of quantification of 30.4 pg/mL and 21.9 pg/mL were achieved with satisfactory accuracy for ITO-APTES-mVero and ITO-APTES-mCalu, respectively. Selectivity studies revealed that this platform was able to differentiate the target spike proteins from NS1 proteins from dengue and Zika viruses. The use of biorecognition between cell membranes that express the ACE-2 receptors and the virus spike protein may be a new and efficient way to diagnose SARS-CoV-2, especially in terms of the cost of production and isolation, when compared to other targets.

References:

1 J. Cancino-Bernardi, E. J. Comparetti, N. N. Ferreira, R. R. Miranda, M. M. Tuesta, I. Sampaio, P. I. Costa and V. Zucolotto, Talanta,
2023, 253, 124008.

2 N. F. Noronha, J. Cancino-Bernardi, V. M. O. Cardoso, E. J. Comparetti, R. R. Miranda, L. M. B. Ferreira, V. Zucolotto. Chapter 13. In: Smart nanomaterials for bioencapsulation. Ed. Amsterdam: Elsevier, 2022, 223-232.

3 J. Cancino-Bernardi. Innovation in Nanomedicine - Nanomaterials Camouflaged with Cellular Membrane for Application in Therapies. Bio. J. Sci. & Tech. Res., 2018, 8, 1-3.