bluuebunny/crossref_metadata_2025 huggingface dataset:
Composition Optimization of Triple Conducting PrNixCo1-XO3-δ Oxygen Electrodes for Protonic Ceramic Electrochemical Cells
Authors: Tang Wei , Ding Hanping , Luo Hongmei , Zhou Meng , Ding Dong
Published: July 2021

Using protonic ceramic electrochemical cells (PCECs) to produce hydrogen is a promising approach to achieve the renewable energy storage, and development of critical materials is the key step to facilitate fast hydrogen production rate. Particularly, the sluggish electrode kinetic at reduced temperatures (400~600 °C) and chemical stability under realistic high steam concentration raises concern. We have recently reported a triple conducting oxide of PrNi0.5Co0.5O3-δ perovskite as an oxygen electrode in PCECs, which exhibits superior electrochemical performance in both fuel cell and electrolysis modes, and potential increased stability due to the absence of alkaline elements such as Ba and Sr in the composition. In this work, the continuous composition optimization of PrNixCo1-xO3-δ (x=0.1, 0.3, 0.5, 0.7, and 0.9) oxides is carried out to find the dependence of Ni/Co ratio on the catalytic activity towards oxygen reduction and water splitting reactions. The isotope water temperature-programmed desorption and thermogravimetric analysis is used to study the water uptake capability for understanding the proton concentration variation as function of doping level. The Fourier-transform infrared spectroscopy (FTIR) is also utilized to observe relative intensity change of the hydroxyl band on electrode surface to further explain the possible species evolution in the relevant reaction modes. This work provides a representative approach on composition optimization for oxygen electrode candidate down selection.
Three-Dimensional Carbon Foam Supported Co3O4/NiO Nanosheets As Non-Enzymatic Electrochemical H2O2 Sensors
Authors: An Mingli , Liu Minmin , Liu Yuyu
Published: July 2021

In the present work, we successfully in-situ synthesized a three-dimensional (3D) carbon foam (CF) supported two-dimensional (2D) cobaltosic oxide/nickel oxide nanosheets through a facile solvothermal reaction assisted with a subsequent annealing procedure. Scanning electron microscopy (SEM) measurements showed that Co3O4/NiO nanosheets were uniformly grown on the 3D carbon framework at 180 °C for 1h which was labled as Co3O4/NiO-NSs/CF-1801. Due to the micron-level porous architecture and the high conductivity of the 3D carbon foam, the obtained composites possess large surface area, fast mass transport and high electronic conductivity. The Co3O4/NiO-NSs/CF-1801 showed a relative low limit of detection (LOD=5.51 µM) and the wide linear detection range (0.20–4.00 mM) with a sensitivity of 7.67 mA mM-1 cm-2. This excellent performance is due to the synergetic effect of micron-level porous architecture of 3D carbon foam and the in-situ uniformly growth of Co3O4/NiO nanosheets, which make them to be promising materials as electrochemical H2O2 sensing catalysts.
Fabrication of Bacterial Cellulose Membrane-Based Alkaline-Exchange Membrane for Application in Electrochemical Reduction of CO2
Authors: Zou Qian Qian , Qiao Jin Li
Published: July 2021

As the core component of the electrochemical reduction of CO2
(ERC), alkaline anion-exchange membranes (AEMs) in a CO2 electrolyzer can not only transport hydroxide ions as conductors, but also prevent fuel crossover between two electrodes and reduce fuel loss. However, the membrane is threatened by low conductivity and poor stability. In this paper, AEMs based on polymer composites of bacterial cellulose (BC)/poly (diallyldimethyl ammonium chloride) (PQ-6, PDDA) are developed for use in ERC, via a proposed impregnation, chemical cross-linking and ion-exchange process. The effects of crosslinking conditions and different BC:PDDA mass ratio on the hydroxide-ion conductivity, water content, microscopic and macroscopic morphological structure, and stability of BC-PDDA-OH- membrane are thoroughly evaluated. The hydroxide-ion conductivity, incorporating BC:PDDA = 1:0.5 mass ratio, remained at 28.5mS cm-1 and 17.89mS cm-1 after the membrane soaking in 0.5M KHCO3 and 0.5M KOH solution for 720h, respectively. At an applied potential of -0.96VRHE, the BC-PDDA-OH- membrane exhibits the highest Faradaic efficiency of 50.84% for formate (FEHCOO-) in 0.5M KHCO3 electrolyte, and the FEHCOO
-
only attenuates by 8.85% after 20 h of continuous electrolysis. In comparison, the BC-PDDA-OH- membrane in 0.5M KOH electrolyte produced the FEHCOO
-
of 50.92% at an applied potential of -1.006VRHE. The electrochemical performances of both systems are superior to that of commercial acidic Nafion117 and commercial alkaline A901 membranes, which prove the feasibility of BC membrane fabricated AEMs application in high performance of ECR.
Sodium-Assisted TiO2 Nanotube Arrays of Novel Electrodes for Photochemical Sensing Platform
Authors: Abdelnasser Shady , Kim Semin , Yoon Hyeonseok , Toth Rita , Pal Kaushik , Bechelany Mikhael
Published: July 2021

In recent years, the study of modified-TiO2 based electrodes has gained great attention to help improve its photo-electrochemical performance. Modifications with metals [1,2], non-metals [3,4], transition metals [5,6] and rare-earth metals [7,8] have been studied; however, research in alkali-modified TiO2 is limited when compared to the aforementioned strategies. Owing to their low first ionization potentials, alkali metals supposed to reduce the total work function of TiO2, which can be an effective way to improve the performance of titania-based catalysts [9]. Herein, we investigate the design and characterization of efficient sodium-modified TiO2 photo-electrodes readily prepared by the electrochemical anodization of titanium metal followed by soaking treatment in aqueous solution containing quantitative NaOH alkaline medium. The crystalline properties revealed no change in the main peak positions and shapes of pristine TiO2 which signifies that the existence of sodium did not affect the crystalline structure of TiO2; the modification was only confined to the surface of the nanotubes. Our analysis of the photo-electric properties showed that the surface modified photo-catalysts exhibited an almost threefold increase in their photocurrent response (0.66 mA cm-2) relevant to the unmodified TiO2 (0.22 mA cm-2) under 1 sun intensity; these feature were ascribed to the former’s remarkable charge separation and mobility. These characteristics were further proved via electrochemical impedance analysis, which indicated that the surface modified catalysts exhibited less charge-transfer resistance as well as lower double layer capacitance. Thus, they maintained improved kinetics for the photo-electrochemical reaction. The surface modified samples also exhibited more negative onset potential (Eonset) relative to the unmodified sample; this was ascribed to the lesser steepness of the band bending of the treated samples which decrease the external bias needed to advance the reaction. This was further verified by our Mott-Schottky analysis, which demonstrates a cathodic shift in the flat band potential in comparison with the pure TiO2.
Bipolar Membrane Electrode Assemblies for Water Electrolysis – Goals and Challenges
Authors: Mayerhöfer Britta , Ehelebe Konrad , Speck Florian Dominik , Bierling Markus , McLaughlin David , Böhm Thomas , Hegelheimer Manuel , Cherevko Serhiy , Peach Retha , Thiele Simon
Published: July 2021

Hydrogen production from water electrolysis is considered a promising large-scale solution for energy storage of intermittent, renewable sources. Besides mature alkaline electrolysis employing caustic KOH solutions as a liquid electrolyte, modern technologies focus on the use of ion exchange membranes as a solid electrolyte. While the widespread application of state of the art proton exchange membrane (PEM) water electrolyzers is impaired by the requirement of costly and rare iridium-based catalyst for the oxygen evolution reaction (OER), anion exchange membranes (AEM) are recently reaching higher technological readiness levels.

Besides the progress in AEM water electrolysis, also the combination of a PEM for the cathode and an AEM for the anode, referred to as bipolar membrane water electrolysis is gaining more scientific interest. As depicted below, the bipolar interface (preferably decorated with a water dissociation (WD) catalyst [1]) enhances the water dissociation rate into protons and hydroxide, which feed the respective electrode reactions.

We have established various modular AEM- and PEM-based building blocks, which allow us to thoroughly investigate zero-gap bipolar membrane electrode assemblies for water electrolysis in various configurations. [2] As the AEM is expected to contribute the most to ohmic losses, we have employed additive manufacturing techniques to decrease the AEM layer thickness stepwise. Moreover, we have evaluated performance determining parameters such as the WD interlayer, operating conditions and water management in the membrane electrode assembly. All these studies allow us a critical assessment of the potential and the drawbacks of this novel MEA system for water electrolysis.

Acknowledgements

This work was performed in collaboration with the National Research Council of Canada in the Materials for Clean Fuels Challenge Program.

References

[1] S. Z. Oener, M. Foster, S. W. Boettcher, Science (2020).

[2] B. Mayerhöfer, D. McLaughlin, T. Böhm, M. Hegelheimer, D. Seeberger and S. Thiele, ACS Appl. Energy Mater. (2020).

Figure 1
(Invited) Theoretical and Experimental Performance Metrics of Doped SrTiO3 Photocatalyst Particles for Visible-Light-Driven H2 Evolution
Authors: Chen Zejie , Watanabe Kenta , Stinson Robert , Barrera Luisa , Keene Sam , Gaieck William , Xu Mingjie , Pan Xiaoqing , Kudo Akihiko , Esposito Daniel V. , Bala Chandran Rohini , Ardo Shane
Published: July 2021

Solar hydrogen production could be a techno-economically viable alternative to steam methane reforming through development of new reactor designs and reaction schemes. Motivated by this fact, my group recently proposed a dual-bed batch reactor for Z-scheme solar water splitting that consists of stacked photocatalyst beds, which aid performance due to serial light absorption and short distances for redox shuttle mass transport. An unexpected discovery based on this design is that an ensemble of optically thin materials is more beneficial to theoretical solar-to-hydrogen conversion efficiencies than a standard single-light-absorber geometry. Through parallel experimental work we have shown that state-of-the-art doped and codoped SrTiO3 H2-evolving photocatalyst particles exhibit variability in homogeneity of dopant distributions, which correlates to overall performance. We have also observed that nanoscale coatings enable selective H2 evolution and desired redox shuttle reactivity over undesired reactions, which theoretically enable increased solar-to-hydrogen conversion efficiencies. Collectively these results provide new design guidelines and additional research pathways for the development of effective composite materials to serve as active components in techno-economically viable solar fuels devices.
Single Stage Reactors for Electrifying Bio-Methanation
Authors: Jayathilake Buddhinie Srimali , Pang Simon H. , Chandrasekaran Swetha , Freyman Megan C. , Deutzmann Jörg S. , Kracke Frauke , Spormann Alfred , Baker Sarah
Published: July 2021

As a combined solution for minimizing CO2 emissions and meeting global energy demands, upgrading CO2 to produce renewable natural gas is an emerging technology to utilize and store renewable energy. When this process is performed by efficient and product selective biocatalysts, conventional and energy intense thermal methanation technologies can be replaced by bio-methanation technology. The bio-methanogenesis process is typically performed with hydrogen produced externally in electrolyzers, but is severely limited by poor mass transport and solubility issues of molecular hydrogen. A system where both electrolysis and microbial conversion are combined in a single reactor helps overcome these problems. However, despite the outstanding opportunities of in-situ electro-bio-methanogenesis, there are challenges of electrified bioreactors that must be overcome, including microbial tolerance and enhancing the kinetics of in-situ hydrogen evolution. Thus, developments to achieve the balance between both biochemical and electrochemical requirements will allow these reactors to achieve optimum performance. The developments include maintaining physiological pH, effective separation of anode and cathode, improving charge transfer kinetics and reducing internal resistance.

We have used our advanced manufacturing capabilities to design and fabricate components for developing electro-bioreactors from 0.1 W scale in sluggish H-cells to MW scale stacks of flow cell CO2 electrolyzers. This allows us to achieve the balance between both biochemical and electrochemical requirements mentioned above. In this study, we show how utilization of high surface area porous 3D electrodes can support maintaining biocompatible conditions near the vicinity of hydrogen evolving electrode at effective rates of electrolysis, while improving both efficiency and productivity of microbial methanogenesis. We have conducted studies to understand the effect of electrode geometry and surface area on energy efficiency and microbial health. Finally, we demonstrate the ability to produce pipeline-quality methane (>97% CH4) from CO2 for an extended period.
(Invited) In Situ Time-Resolved Probe of Charge Carrier Dynamics at Planar Semiconductor Photoelectrode/Liquid Interface
Authors: Lian Tianquan
Published: July 2021

Photoelectrochemical cells are a promising approach for converting solar energy to storable chemical energy in chemical fuels. The efficiency of these devices depends critically on efficient transfer of charge carrier across the electrode liquid interface and the efficiency and selectivity of the catalytic reaction on electrode surface. Although transient absorption spectroscopy is a powerful tool for probing interfacial dynamics in high surface area electrodes, it is often not applicable on planar electrodes because the observed signal is often dominated by carrier dynamics in the bulk. In this talk, we discuss our recent effort in developing in situ time-resolved linear and nonlinear spectroscopic tools that can be used to probe carrier dynamics and reactions at planar electrode/liquid interfaces, focusing on transient reflection spectroscopy. Compared to transient absorption, this method is more sensitive to surface carrier density that can be more directly correlated to catalysis. We showed that transient reflectance change can be used to follow charge carrier dynamics and their amplitude can be directly correlated to IPCE of water reduction on p-GaP single crystals protected by TiO2 ALD layer. Our finding suggests that IPCE is determined by the efficiency of initial ultrafast (< hundreds of ps) charge separation across the GaP/TiO2 interface despite the much slower water reduction reaction. Key loss mechanisms that limits the IPCE are also discussed.
(Invited) Photoelectrochemical Behavior of Transition Metal Alloyed Nitride MXenes
Authors: Neale Nathan R. , Djire Abdoulaye , Wang Xiang , Mirkin Michael V. , Reinhart Benjamin J.
Published: July 2021

Two-dimensional (2D) MXenes based on early transition metal carbides and nitrides have highly tunable electrochemical properties including excellent catalytic activity for solar fuels generation. These properties can be manipulated by modifying the basal plane chemistry. In this presentation, we will describe our recent development of mixed transition metal nitride MXenes, M-Ti4N3Tx (M = V, Cr, Mo, or Mn; Tx = O and/or OH), by modifying pristine exfoliated Ti4N3Tx MXene with V, Cr, Mo, and Mn salts using a simple solution-based method. We will show that the transition metal alloying process induces highly tunable hydrogen evolution reaction (HER) electrocatalytic activity in 0.5 M H2SO4 electrolyte as follows: V-Ti4N3Tx > Cr-Ti4N3Tx > Mo-Ti4N3Tx > Mn-Ti4N3Tx > pristine Ti4N3Tx with overpotentials as low as 330 mV at –10 mA cm–2. We further characterize these M-Ti4N3Tx MXenes using scanning electrochemical microscopy (SECM) to demonstrate that catalytic activity occurs on the basal plane, and additionally show that these MXenes exhibit semiconducting behavior. Lastly, we use in situ X-ray absorption spectroelectrochemistry to probe the transition metal oxidation states and unveil the mechanism of HER electrocatalysis.
(Invited) Strategies in Colloidal Catalysis for Generation of Solar Fuels
Authors: Arcudi Francesca , Yang Muwen , Schatz George , Weiss Emily A.
Published: July 2021

This talk will describe two separate strategies to use colloidal semiconductor nanocrystals to photocatalytically produce (i) the fuel intermediate CO from the abundant feedstock CO2, and (ii) H2 from protons within a hydrogel with pH-dependent structure. CO2 reduction is accomplished with record turnover in pure water with a combination of colloidal CuInS2 nanocrystals and a cobalt porphyrin electrocatalyst. The nanocrystals are decorated with partially protonated amine-terminated ligands, which not only provide a means of electrostatic self-assembly with the negatively charge porphyrin, but also allow pre-activation of the CO2 through formation of carbamic acid. In a separate system based on cadmium chalcogenide nanorods, the yield of proton reduction is non-monotonically dependent on the pH of the hydrogel with a large spike near the pKa of the exposed amine groups within the gel.
The Synthesis of Nano-Heterostructures (metal-metal oxide) By Thermal Oxidation for Artificial Photosynthesis Process
Authors: Cigarroa-Mayorga Oscar E.
Published: July 2021

In this work, heterostructures based on the junction metal-metal oxide were synthesized by the accessible method of thermal oxidation. Particularly the copper oxide nanowires (CuO-Nw) with gold nanoparticles (AuNPs) and molybdenum oxide nanorods (MoO3-nr) with AuNPs are presented.

Both kind of samples were obtained from a metallic foil (Cu foil for CuO-Nw and Mo foil for MoO3-nr). The foils were cut and etched with 1 M nitric acid solution for 10 seconds, then put in deionized water for 15 min and finally isothermally heated into a horizontal furnace. The CuO-Nw with AuNPs were achieved by a two-step methodology. In the thermal treatment, the oxygen in atmosphere inside the furnace was controlled within 21 wt. % ± 1 wt. % content and a 20 L/min flux rate was used. The experiments were carried out at 400, 500 and 600 °C under a for 1h, 3h, and 5h. Afterward, Cu-O Nw were Au-coated by sputtering. with Au was coated by sputtering Au films with 10 nm and 60 nm in thickness were deposited. In order to synthetize the AuNPs a thermal treatment was isothermally performed under nitrogen atmosphere at 450 °C for 15 min. On the other hand, heterostructures formed by MoO3-nr and AuNPs were obtained by one step thermal oxidation (TO). After the cleaning step, the TO was performed on Mo foil coated with Au. The oxidation was performed into a furnace with a 20 wt. % oxygen atmosphere at 500 °C, 600 °C and 700 °C. In order to determine the relationship between oxidation time exposure and the obtained structure morphology, each experiment was performed for 1 h, 3 h and 5 h. To guaranty reproducibility, the experiments were performed by triplicated in separated experiments.

The samples were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, selected area of electron diffraction in each step of the synthesis process. The effect of temperature and time on density, diameter, and length of nanostructures was studied. The possible application of this kind of nano-heterostructures in the artificial photosynthesis process is discussed.

Acknowledgments

The authors acknowledge the Secretaría de Investigación y Posgrado of the Instituto Politécnico Nacional for the economic support to this work. There is no conflict of interest to disclosure.
Electrochemical Reduction of CO2 to Ethylene with Coproduction of Glycolic Acid Via Glycerol Oxidation
Authors: Khan Mohd Adnan , Nabil Shariful Kibria , Al-Attas Tareq A. , Hu Jinguang , Kibria Md Golam
Published: July 2021

We are in a race against time to implement technologies for carbon capture, conversion, and utilization (CCU) to create a closed anthropogenic carbon cycle. Renewable energy powered electrochemical CO2 reduction (eCO2R) to fuels and chemicals is an attractive technology in this context. Here, we demonstrate a strategy to drive economic feasibility of eCO2R to ethylene (C2H4), the largest produced organic chemical, by coupling with glycerol oxidation on anode. Our gold nano-dendrite anode catalyst demonstrated very high activity (J ~377 mA/cm2 at 1.2 V vs RHE) and selectivity (~50% to glycolic acid (GA)) for glycerol oxidation. The co-electrolysis process demonstrated record high selectivity of ~60% for C2H4 production at a very low cell voltage of ~ 1.7 V, translating to 32% reduction in required energy compared to conventional eCO2R with water oxidation reaction on anode. The experimental results were complemented with a detailed technoeconomic analysis that indicated economic feasibility will depend on several factors such as price of organic feed, selectivity of anode electrode, market value of chemicals produced and most importantly cost of separation and purification. Our results indicate that C2H4 produced via conventional eCO2R would require electricity price to plummet to <1 cents/kWh to be cost-competitive, while a co-electrolysis process to produce C2H4 and GA will help reduce C2H4 production cost by ~ 80 % to ~1.08 $/kg, reaching cost parity at electricity price of 5 cents/kWh. This study may trigger research efforts for design of electrochemical processes with low electricity requirement using cheap industrial waste streams.
Comparative Life Cycle Assessment of CO2 Electrosynthesis to Fuels and Feedstocks
Authors: Nabil Shariful Kibria , McCoy Sean , Kibria Md Golam
Published: July 2021

Development of electrochemical pathways to convert CO2 into fuels and feedstock is rapidly progressing over the past decade. Here we present a comparative cradle-to-gate life cycle assessment (LCA) of one and two-step electrochemical conversion of CO2 to eight major value-added products; wherein we consider CO2 capture, conversion and product separation in our process model. We measure the carbon intensity (i.e., global warming impact) of one and two-step electrochemical routes with its counterparts – thermochemical CO2 utilization and fossil-fuel based incumbent synthesis routes for those products. Due to inevitable carbonate formation or CO2 crossover in one-step CO2 electrolysis using neutral pH membrane electrode assembly, the two-step electrosynthesis pathways (CO2 to CO in solid oxide electrolysis cell followed by CO electroreduction in alkaline flow cell) would be distinctively compelling through the lens of climate benefits. This analysis further reveals that the carbon intensity of electrosynthesis products is due to significant energy requirement for conversion (75–85% of total energy consumption for gas products) and product separation (30–85% of total energy consumption for liquid products) phases. Electrochemical route is highly sensitive to the electricity emission intensity and is compelling only when coupled with low emission intensity (<0.25 kg CO2e per kWh). As the technology advances, we identify near-term compelling products that would provide climate benefits over incumbent routes, including syngas, ethylene and n-propanol. We further identify technological goals required for electrochemical route to be competitive, notably achieving liquid product concentration >20 wt%. It is our hope that this analysis will guide the CO2 electrosynthesis community to target achieving these technological goals, such that when coupled with low-carbon electricity, electrochemical route would bring climate benefits in near future.
(Invited) Mass Transport Considerations for High Performance CO2 Electrolysers
Authors: Smith Wilson
Published: July 2021

Electrocatalytic CO2 reduction has the dual-promise of neutralizing carbon emissions in the near future, while providing a long-term pathway to create energy-dense chemicals and fuels from atmospheric and waste CO2. The field has advanced immensely in recent years, taking significant strides towards commercial realization. Gas diffusion electrodes (GDEs), composed of solid electrocatalysts on porous supports positioned near the interface of a conducting electrolyte and CO2 gas, have been able to demonstrate the substantial current densities needed for future commercialization. These higher reaction rates have often been ascribed to the presence of a three-phase interface, where solid, liquid, and gas provide electrons, water, and CO2, respectively. Conversely, mechanistic work on electrochemical reactions implicate a fully two-phase reaction interface, where gas molecules reach the electrocatalyst’s surface by dissolution and diffusion through the electrolyte. Here, we first outline the macro, micro and atomistic phenomena occurring within a gas-diffusion electrode to provide a focused introduction to the architecture of the often-discussed three-phase region for CO2 electrolysis.

In addition, we use a 2-D model to examine the concentration gradients in the gas and electrolyte flow channels across a GDE, which provides longitudinal information along the length of a flow cell. In doing so, we quantify the extent of concentration overpotentials and ohmic drops throughout the catalyst layer across a range of applied potentials and flow rates. Various process parameters were modified to explore the effects on the CO2 mass transfer-limited current density, conversion, and outlet concentrations of CO2, CO and H2. Our model suggests that ohmic losses largely determine the current density distributions at low conversion rates where small gradients in concentration exist. However, as the concentration profiles become less uniform (e.g. high conversion rates), the non-electrochemical consumption of CO2 starts to overtake electrochemical conversion, and leads to non-uniform performance across the electrode. In addition, while higher flow rates allow the ability to substantially increase current density, this comes at the expense of ohmic drops and losses in selectivity, which become more prominent at high conversion rates. The ability to understand the interplay between process conditions and local environment will be necessary to further develop the science and technology of electrochemical CO2 reduction.
(Invited) Paired Flow Electrolyzers for Furanic Compounds Conversion to Valuable Chemicals
Authors: Liu Hengzhou , Lee Ting-Han , Cochran Eric W , Li Wenzhen
Published: July 2021

Paired electrolysis has been emerged as an electricity-powered platform for converting biorewable feedstock to higher-valued chemicals at both the cathode and anode. In this presentation, we explored paired electrolyzers of different architectures with remarkable performance and stability. We first designed three-electrode flow electrolyzers to pair electrocatalytic hydrogenation of 5-(hydroxymethyl)furfural (HMF) on oxide-derived silver electrode and TEMPO-mediated HMF oxidation on carbon cloth. The paired flow cell achieved a combined faradaic efficiency of 163% to desired 2,5-bis(hydroxymethyl)furan (BHMF) and 2,5-furandicarboxylic acid (FDCA) with a cell potential of ~1.7 V, at the constant current of 10 mA. When the anodic reaction was replaced by hydrogen oxidation, a minimized cell voltage of only ~0.9 V was achieved. We then assmbled a membrane electrode assembly (MEA)-based two-electrode flow cell, which realized a minimized cell potential of only ~1.5 V for a continuous 24 hours paired electrolysis of HMF. Finally, a pH asymmetric architecture was designed to match the optimum reaction conditions and to replace HMF oxidation on a NiFeOOH anode catalyst without a redox mediator. Our recent development of electrochemical-chemical combined reactors for furanic compounds conversion will also be briefly presented.
(Invited) Advanced Catalysts for Efficient Electrochemical Ammonia Oxidation
Authors: Li Yi , Wu Gang
Published: July 2021

Ammonia (NH3) has proved to be an effective alternative to hydrogen in low-temperature fuel cells via its direct ammonia oxidation reaction (AOR)(1). However, the kinetically sluggish AOR has prohibitively hindered the attractive direct ammonia fuel cell (DAFC) applications. Here, we report an efficient AOR catalyst, in which ternary PtIrM (M: Ni or Zn) alloy nanoparticles well dispersed on a binary composite support consisting of porous silicon dioxide (SiO2) and carboxyl-functionalized carbon nanotube (PtIrNi/SiO2-CNT-COOH) through a sonochemical-assisted synthesis method (2). The PtIrNi alloy nanoparticles, with the aid of abundant OHad provided by porous SiO2 and the improved electrical conductivity by CNTs, exhibit remarkable catalytic activity for the AOR in alkaline media. It is evidenced by a lower onset potential (∼0.40 V vs reversible hydrogen electrode (RHE)) at room temperature than that of commercial PtIr/C (ca. 0.43 V vs RHE). Increasing NH3 concentrations and operation temperatures can significantly enhance AOR activity of this PtIrNi nanoparticle catalyst. Specifically, the catalyst at the temperature of 80 °C exhibits a much lower onset potential (∼0.32 V vs RHE) and a higher peak current density, indicating that DAFCs operated at a higher temperature are favorable for increased performance.

References

(1) Adli, N. M.; Zhang, H.; Mukherjee, S.; Wu, G., Review—Ammonia Oxidation Electrocatalysis for Hydrogen Generation and Fuel Cells. Journal of The Electrochemical Society 2018, 165 (15), J3130-J3147.

(2) Li, Y.; Li, X.; Pillai, H. S.; Lattimer, J.; Mohd Adli, N.; Karakalos, S.; Chen, M.; Guo, L.; Xu, H.; Yang, J.; Su, D.; Xin, H.; Wu, G., Ternary PtIrNi Catalysts for Efficient Electrochemical Ammonia Oxidation. ACS Catalysis 2020, 10 (7), 3945-3957.
The Effects of CeO2 Inclusion in the Electrocatalytic Properties of Nanoparticles for an Ammonia Oxidation Electrocatalyst
Authors: Padin Jose , Huertas Namir Andrea , Cunci Lisandro
Published: July 2021

Abstract

In the quest for advancing renewable energy technologies with high energy density fuels, a certain interest in Fuel Cells has been developed. Currently the focus is on nitrogen containing fuels, such as ammonia (). This primarily because the oxidation will predominantly yield dinitrogen (). This means that these sustainable fuel cells can render a carbon free energy process. For the electro-oxidation of ammonia () an electrocatalyst is required to catalyze the reaction. This is due to the fact that the ammonia oxidation reaction is difficult and can only be achieved on noble metals (). Because of this, there are complications on an industrial scale application since is not cost efficient. The project aims to develop an ammonia alkaline fuel cell (AAFC) using -based nanocatalyst to enhance the ammonia electro-oxidation. Different precursors ( vs ) were used to analyze the electrocatalytic effects of metal oxide addition (Fe2O3 vs CeO2) and the potential for ammonia oxidation. To determine the correct conditions to add the metal oxides onto the nanoparticles, two protocols were established. In protocol 1, was added before the particle cleaning procedure. In protocol 2, was added after the cleaning procedure. The Cyclic Voltammetry method was then applied to study the electrocatalytic activities of alloys at 20 mV/s scan rate. For the results from protocol 1, the addition of on samples from showed a slight shift to lower onset potential, meanwhile in samples from the precursor this did not occur. Onset potential was reduced form -0.386 V (control sample from without ) to -0.472 V when was added with 20 min sonication. The behavior for onset potential from protocol 2 was similar to protocol 1, but more electrical noise is visible with this protocol for samples from the precursor. According to its more defined hydrogen peak separation from the hydrogen desorption region and the energetic difference in the -oxide reduction region the nonchlorinated precursor shows better facet exposure. Through a combined analysis of SEM images and electrochemical experiments, a difference in electrochemical surface area was seen. For the chlorinated precursor () 22.0 electrochemical surface area was found while the nonchlorinated precursor ( ) had 12.8. The addition to the nanoparticles significantly reduced the electrochemical surface area in both precursors. No significant difference was found between the onset potential for the ammonia oxidation of particles and precursors. Currently we are exploring the electrocatalytic activities of nanoparticles when combined with Fe2O3.
Urea Oxidation Electrocatalysis on Nickel Hydroxide: The Role of Disorder
Authors: Offen Polak Inbal , Chakrabarty Sankalpita , Burshtein Tomer , Farber Eliyahu , Kornblum Lior , Eisenberg David
Published: July 2021

The urea oxidation reaction (UOR) is an important challenge in electrocatalysis, in the context of electrolyzers, fuel cells, medical sensing, and bio-waste treatment. The leading electrocatalysts for the UOR are nickel hydroxide surfaces, operating by the Botte mechanism: NiII(OH)2 is oxidized to NiIIIOOH, and the latter drives the UOR. However, these materials have several polymorphs, with α- and β-Ni(OH)2, and γ- and β-NiOOH, as described by the Bode diagram. We now report a systematic study of a series of nickel hydroxides, varying gradually from α-rich to β-rich materials. The crystallinity, order, hydration, intercalation, and morphology of these materials have been characterized by XRD, Raman, ATR-FTIR, XPS, and HRSEM and linked to their electrochemical activity. The disordered α phase was found to be superior to the β phase as a UOR electrocatalyst, with an oxidation onset potential of 0.31 V vs. SCE, better reversibility, and higher anodic current densities. Moreover, the perfect match in onset potentials between UOR electrocatalysis and the Ni2+/Ni3+ oxidation was observed for both phases, suggesting that the Botte mechanism is true for both the α-Ni(OH)2/γ-NiOOH couple and the β-Ni(OH)2/β-NiOOH couple. We further characterize the dynamic behavior of these materials (activation and aging), allowing us to propose a unified Botte-Bode diagram of UOR on Ni(OH)2/NiOOH.
Efficient Bipolar Membrane Water Electrolysis Enabled By Dual-Phase CoP-CoTe2 Nanowires As Bifunctional Electrocatalyst
Authors: Amorim Isilda , Xu Junyuan , Yu Zhipeng , Bento Fátima , Liu Lifeng
Published: July 2021

Water splitting offers an environmentally friendly way for H2 production, especially if the electricity comes from renewable sources such as solar and wind. Significant effort has recently been made to developing cheap and efficient earth-abundant electrocatalysts to make electrolyzed hydrogen economically competitive. Although the substantial progress, the operational voltage of water splitting in a single electrolyte system is still high. Given that the hydrogen evolution reaction (HER) is kinetically favorable in acidic conditions and the oxygen evolution reaction (OER) in alkaline conditions, it would be preferable to realize these half reactions simultaneously in different electrolytes in a single electrolyzer. Moreover, such cell design allows the using of low-cost and earth-abundant catalysts for both HER and OER.

In this work we demonstrate the development of a dual-phase cobalt phosphide-cobalt ditelluride (CoP-CoTe2) nanowires, which can be used as efficient bifunctional electrocatalysts for both HER and OER using acid-alkaline dual electrolytes in a two-compartment cell separated by a bipolar membrane (BPM). Using the BPM under "reverse bias" configuration, the bipolar membrane overall water splitting can be accomplished with an onset voltage as low as 1.13 V and a voltage of 1.72 V is needed to deliver 10 mA cm-2. However, water electrolysis can be accomplished at significantly lower external biases, e.g. 1.01 V at 10 mA cm-2, when a "forward bias" conditions was used due to the assistance of electrochemical neutralization. Moreover, this electrolyzer can sustain water splitting for at least 100 h. The bipolar membrane water electrolysis, particularly with the "forward bias" configuration, shows great promise as an alternative to the current technologies.
Multifunctional Noble Metal Phosphide Electrocatalysts for the Organic Molecule Electro-Oxidation
Authors: Yu Zhipeng , Wei Xian-Kui , Xu Junyuan , Li Yue , Araújo Ana , Amorim Isilda , Faria Joaquim Luis , Dunin-Borkowski Rafal E. , Liu Lifeng
Published: July 2021

The small organic molecule electro-oxidation (OMEO) is the important anodic reaction occurring in direct liquid fuel cells (DLFCs), whose kinetics are largely hindered by the low activity and poor stability of electrocatalysts. Noble metals (e.g. Pt, Pd) are currently the state-of-the-art catalysts for the OMEO; however, for practical applications their electrocatalytic performance needs to be improved. Herein, we demonstrate that a simple phosphorization treatment at different temperatures is able to convert commercially available supported noble metal catalysts (PdNi, Pd) into multifunctional metal phosphide (PdNiP) or phosphide-metal heterostructures (PdP2-Pd/C), which exhibit substantially enhanced electrocatalytic performance toward a number of OMEO model reactions including the formic acid oxidation reaction (FAOR), methanol oxidation reaction (MOR), ethanol oxidation reaction (EOR), and ethylene glycol oxidation reaction (EGOR), in terms of not only apparent activity, but also of specific and mass activities, poisoning tolerance and catalytic stability. The improved performance and stability results from the modification of electronic structure by the introduced phosphor and synergy between of multinary structure (PdP and NiP, PdP2 and Pd), where the formed phosphide facilitates the adsorption of hydroxyl species and promotes the oxidation of poisoning intermediates giving rise to improved activity, poisoning tolerance and stability. The simple phosphorization approach reported here allows for mass production of highly-active electrocatalytic performance toward multiple OMEO reactions, holding substantial promise for their large-scale application in DLFCs.
Signaling Studies of Protein-Peptide Binding on Microelectrode Arrays
Authors: White-Drayton Kendra , Liu Siyue , Moeller Kevin D
Published: July 2021

Electrochemical methods provide unique opportunities for non-traditional synthesis and analytical studies. Using electrochemistry, we are able to synthesize addressable molecular surfaces on microelectrode arrays and then utilize the surface to probe interactions between receptors and their biological targets. To this end, the electrodes on the surface are individually addressable. They can be used as synthetic tools to generate reagents and catalysts and in so doing trigger chemical reactions on the surface of the array above the electrodes. This allows us to synthesize and/or place molecules on the arrays directly above specific individually addressable electrode in the arrays that can then be used to study the binding behavior of those molecules. While this work has shown to be successful, significant challenges still remain. While the binding signals can be observed for peptide – protein interactions on the functionalized surface of the array, the signals obtained are amplified due to avidity effects. This amplification creates difficulties when it comes to comparing the data obtained on an array to the to existing binding data in the literature. At times, it makes it difficult to quantify a binding event at all since the amplification can shift a binding curve to a point where part of it cannot be observed. Therefore, it is extremely important to develop methods by which we can calibrate the signals produced and recorded on the microelectrode arrays and optimize those signals in a reproducible way. For this reason, we have been exploring how the nature of the functionalized array surface influences the binding signal. Our work is exploring how the relative concentration of molecules on the surface of the array can be used tune the value of the binding constant measured for an interaction on a microelectrode array, how the use and length of a linker between the molecule being studied and the array can be used to optimize the intensity of the signal, and how adjusting the hydrophilicity of the functionalized surface can be used to increase the signal to noise associated with the experiments. This work will be discussed along with ways to trouble shoot experiments in connection with surface versus solution issues that can arise.

Reference: Nai-Hua Yeh, Yu Zhu, and Kevin D. Moeller*, ChemElectroChem
2019, 6, pp 4134-4143
Polyether-Cyclodextrin Modified Surfaces for Sensing of Hydrophobic Molecules
Authors: Panahi Zahra , Halpern Jeffrey M
Published: July 2021

Electrochemical Impedance Spectroscopy (EIS) is a broadly used technique to study various surface phenomena in soft matter. For development of cyclodextrin based biosensors, we employ faradaic EIS in the presence of ferri/ferrocyanide to characterize polymer modified surfaces, investigate polymer conformational changes, and evaluate reusability and stability of the biosensors (1).

Cyclodextrins consisting of six (αCD), seven (βCD), or eight (γCD) glucose units are composed of a hydrophobic inner cavity and a hydrophilic outer surface. Hydrophobic inner cavity of cyclodextrins have made them promising candidates as molecular receptors for detection of hydrophobic molecules such as trans-resveratrol and cortisol. Health-benefiting effects of trans-resveratrol have been reported in various studies, including those reviewed by Prof. Denis Petters (2). Development of a reusable sensor platform for monitoring hydrophobic species could aid in pharmacokinetics studies and metabolite profiling of trans-resveratrol.

To make a reusable resveratrol biosensor, we first modify the gold electrode surface with polyethylene glycol (PEG). The PEG modified surface is then complexed with αCD. The αCD molecules are released from the surface in the presence of trans-resveratrol, which causes PEG molecules to flatten into a bent-over configuration which decreases the electron transfer rate. The surface can be regenerated by αCD reloading, which results in PEG chains forming microcrystalline channel-type domains and increases the electron transfer rate. With the assistance of EIS, we can confirm the charge transfer resistance increase by αCD release and charge transfer resistance increase by αCD reload. Moreover, Nyquist plots of consecutive reloading and release of αCD indicate that the PEG-αCD surface can successfully be regenerated for at least three time.

Herein, we will detail our PEG-αCD surface for the detection of resveratrol and our PPG-βCD surface for the detection of cortisol. These surfaces behave similarly in their surface configuration state and EIS analysis. Further investigation in the reusability indicates the modified gold surfaces can be reused for three times but fail when regenerated for more than four times. We assume this limitation is imposed by low stability of gold–thiol bonds, and we will discuss our progress to overcome this issue in studying the formation of more stable covalent bonds through aryl diazonium salts.

Acknowledgments: This work was supported by NIH P20 GM113131.

References

Panahi Z, Merrill MA, Halpern JM. Reusable Cyclodextrin-Based Electrochemical Platform for Detection of trans-Resveratrol. ACS Appl Polym Mater. 2020 Nov 13; 2(11):5086–93. Available from: https://dx.doi.org/10.1021/acsapm.0c00866

Rauf A, Imran M, Sulera HAR, Ahmad B, Peters DG, Mubarak MS. A comprehensive review of the health perspectives of resveratrol. Vol. 8, Food and Function. Royal Society of Chemistry; 2017. p. 4284–305. Available from: https://pubs.rsc.org/en/content/articlehtml/2017/fo/c7fo01300k
Building Addressable Libraries: Olefin Functionalization Reactions and the Development of a Site-Selective, Cleavable Linker
Authors: Yeh Nai-Hua , Huang Albert , Moeller Kevin D
Published: July 2021

Microelectrode arrays are potentially powerful tools for monitoring molecular interactions between small molecules and biological targets in "real-time". Yet while the potential for the arrays is coming into focus, there are still barriers that prevent us from taking full advantage of the devices. Chief among these is the need to construct and characterize molecules on the arrays so that they are specifically located by individually addressable electrodes or groups of electrodes in the array. Currently, we are working on methods to construct larger molecular libraries directly on the arrays, an effort that seeks to avoid transferring the libraries to the array one member at a time. To do so, we need to expand the synthetic toolbox available on the arrays. In that context, olefin functionalization is one of the most powerful strategies in modern organic chemistry because it converts readily available double bonds into a wide array of functional groups. For this reason, we are initially examining the role of cis-dihydroxylation, epoxidation, and diazidation reactions which can play in a site-selective array-based synthesis. The chemistry is already paying dividends. In one application, we have shown that a site-selective cis-hydroxylation reaction can enable a new “safety-catch" linker strategy that is completely orthogonal to the typical deprotection strategies used for diversity of oriented syntheses. The result provides a foundation for future synthetic efforts because it enables full characterization of molecules synthesized by any electrode in an array. In this poster, we will discuss progress towards additional array-based olefin functionalization reactions as well as detail the safety-catch linker strategy mentioned above.

Figure 1
Electrocatalytic Nuclear Hydrogenation of Benzoic Acids in a Proton Exchange Membrane Reactor
Authors: Atobe Mahito , Fukazawa Atsushi , Shida Naoki
Published: July 2021

The nuclear hydrogenation of aromatic substrates to obtain saturated cyclic compounds is of great importance in the field of chemical and pharmaceutical industry, due to its readily obtained feedstocks, environmentally friendly and straightforward routes.1 For instance, the chemoselective hydrogenation of benzoic acids to cyclohexanecarboxylic acids has attracted great attention, as the hydrogenated products cyclohexanecarboxylic acids are important organic intermediates for pharmaceuticals, such as praziquantel, caprolactam, and ansatrienin.

Several efficient catalysts based on monometallic Pd, Pt, Rh, and Ru and several alloys have been explored for the aromatic nuclear hydrogenation of benzoic acid and its derivatives.2 However, most of the catalytic reactions were performed under a high pressure of hydrogen gas, which leads to safety concerns. Therefore, the development of hydrogenation of benzoic acids to cyclohexanecarboxylic acids under mild conditions is still a challenging target.

Under these backgrounds, we have demonstrated electrocatalytic nuclear hydrogenation in a proton exchange membrane (PEM) reactor (Figure 1). This system has several merits such as easy separation and recycle use of catalysts, operation under mild and benign conditions.3 We found that the use of PEM reactor with PtRu catalyst gave the corresponding cyclohexanecarboxylic acids with excellent current efficiencies in our demonstrations.

Acknowledgement

The authors gratefully acknowledge supports by a CREST (JST Grant No.: JP65R1204400), Japan.

References

L. Zhang, J. Dong, X. L. Qiao, J. R. Qin, H. F. Sun, A. Q. Wang, L. B. Niu, G. Y. Bai, J. Catal., 372, 258–265 (2019).

D. Dwivedi, R. K. Rai, K. Gupta, S. K. Singh, ChemCatChem, 9, 1930 – 1938 (2017).

Fukazawa, J. Minoshima, K. Tanaka,Y. Hashimoto, Y. Kobori, Y. Sato, M. Atobe, ACS Sustain. Chem. Eng., 7, 11050-11055 (2019).

Figure 1