Electrochemical Conversion Devices Research Articles

Evolution and Reconstruction of Air-Electrode Surface Composition in Reversible Protonic Ceramic Cells: Mechanisms, Impacts on Catalytic Performance, and Optimization Strategies - A Review.

Reversible protonic ceramic cells (R-PCCs) are at the forefront of electrochemical conversion devices, capable of reversibly and efficiently converting chemical energy into electricity at intermediate temperatures (350-700°C) with zero carbon emissions. However, slow surface catalytic reactions at the air-electrode often hinder their performance and durability. The electrode surface is not merely an extension of the bulk structure, equilibrium reconstruction can lead to significantly different crystal-plane terminations and morphologies, which are influenced by material's intrinsic properties and external reaction conditions. Understanding electrode surface evolution at elevated temperatures in water-containing, oxidative atmospheres presents significant importance. In this review, a comprehensive summary of recent processes in applying advanced characterization techniques for high-temperature electrode surfaces is provided, exploring the correlations between surface evolution and performance fluctuations by examining the structural evolution and reconstruction of various air-electrode surfaces associated with degradation and activation phenomena, offering insights into their impact on electrode performance. Furthermore, reported strategies and recent advances in enhancing the electrochemical performance of R-PCCs through engineering air-electrode surfaces is discussed. This review offers valuable insights into surface evolution in R-PCCs and is expected to guide future developments in high-temperature catalysis, solid-state ionics, and energy materials.

Accelerating Discovery of Spinel Oxides for Bifunctional Oxygen Electrocatalysts

The increasing demand for sustainable energy has prompted extensive investigations into electrochemical conversion devices such as fuel cells, water splitting systems, and metal-air batteries. The efficiency of bifunctional oxygen electrodes plays a crucial role in overall electrochemical performance. In recent times, spinel oxides (AB2O4) have emerged as promising candidates for this purpose; however, the limited prior research emphasizes the necessity for a thorough and exhaustive exploration. This study introduces a computational framework that combines machine learning techniques with density functional theory calculations to systematically screen 1240 spinel oxides. Stability evaluations are guided by geometric relation and crystal-likeness score. A metal/nonmetal classifier based on transfer learning is utilized to address data scarcity, thereby improving prediction accuracy. Several selected candidates exhibit superior performance compared to the benchmarking perovskite oxide. Furthermore, we emphasize their potential as mixed ionic and electronic conductors, featuring a network of ion diffusion pathways. This research establishes design principles for the development of high-performance spinel oxide bifunctional oxygen electrocatalysts.

A Machine Learning‐Enhanced Framework for the Accelerated Development of Spinel Oxide Electrocatalysts

AbstractThe surging demand for sustainable energy has spurred intensive research into electrochemical conversion devices such as fuel cells, water splitting, and metal‐air batteries. The performance of oxygen electrocatalysts significantly impacts overall electrochemical efficiency. Recently, spinel oxides (AB2O4) have emerged as promising candidates; however, the scarcity of prior studies underscores the need for a thorough and comprehensive exploration. This study presents a computational framework that integrates machine learning and density functional theory (DFT) calculations for the systematic screening of 1240 spinel oxides. The data scarcity is addressed while enhancing prediction accuracy. Selected candidates are identified to outperform the benchmarking perovskite oxide. Additionally, their potential as mixed ionic and electronic conductors with a 3D network of ion diffusion pathways is highlighted. To further enhance the understanding and prediction of stability, catalytic activity, and reaction mechanisms, a new undemanding descriptor is introduced: the covalency indicator. This study offers a design principle for the development of high‐performance spinel oxide oxygen electrocatalysts.

Numerical study of electrode permeability influence on planar SOFC performance

A solid oxide fuel cell (SOFC) is a clean and very efficient electrochemical conversion device, which generates electricity directly from fuel electrochemical oxidation. In this paper, a three dimensional numerical model has been developed in order to analyse the role of some thermophysical and morphological parameters on the performance of the SOFC cell. In particular, we studied the effect of the variation of permeability of the electrodes: fuel distribution, ionic and electric current density, pressure and diffusion flux are analyzed and compared. The volume fraction of the ionic and electronic phase in the electrodes is studied using a parametric study. It was shown that the current density enhanced by decreasing the permeability, up to a defined value, and it diminished with very small permeability. A remarkable influence of pressure and diffusion of species on the performance of the cell, with the variation of permeability, has been recognized. Varying the permeability in the active layer of electrodes has a large impact on the current density, connected to the volume fraction of ionic phase. This study permits to comprehend the relationship between the performance and microstructure of SOFCs. Meanwhile, it furnishes theoretical guidance for an optimum design of the electrode permeability.

Breaking Free - Unlocking the Potential of Dynamic Hydrogen Bubble Templating Materials

In recent years, porous electrodes for electrochemical conversion devices, such as low-temperature fuel cells or water electrolyzers, have been engineered to address issues related to mass transport to and within the catalyst. For example, the addition of a layer with reduced pore size facing the catalyst layer (i.e., microporous layer) results in an increased performance[1–3]. Furthermore, chemical[4], as well as mechanical[5,6]. methods of creating dedicated liquid and gas pathways in the porous electrodes, have been investigated with promising results, highlighting the need for further optimization of state-of-the-art materials with regards to multi-phase transport. The range of possible modifications is intrinsically limited by the microstructure of the material they are applied to and add cost and complexity to the already costly electrode production procedure, motivating the development of novel materials which contain these desired features, offer a large morphological design space, and are cost competitive.To tackle these stringent targets, we investigate the dynamic hydrogen bubble templating (DHBT) method to generate hierarchical structures containing both a pore size gradient as well as dedicated water and gas pathways in the form of bimodal pore size distributions. It leverages simultaneous deposition of a metal and gas evolution on the same surface to form complex structures from solution using electricity. It results in a hierarchical structure of primary pores (~5-40 µm) separated by porous walls containing secondary pores (10-1000 nm) . This type of material has been used successfully to improve boiling heat transfer[7], another process limited by the counterflow of liquid and gas. They have also been investigated as high surface area material for microbial anodes[8] and have been postulated to be appealing in other electrochemical devices such as batteries or fuel cells[9]. A significant hurdle to unlock the full potential of DHBT foams is the attachment of the foam to the solid electrode surface it is generated on. The presence of the electrode blocks the transport of media in the through-plane direction of the foam and thereby prevents its use in many electrochemical applications. Due to its fragile nature, separation of the foam from this surface easily damages the structure, which is why previous research was done exclusively in the presence of the electrode. Overcoming this limitation would enable new applications for DHBT foams and has the potential to address a wide range of problems in electrochemical systems related to porous media.In this talk, I will discuss our work towards creating free-standing, hierarchically structured metal electrodes through DHBT and the developments needed to adapt this material for the use in electrochemical systems. Owing to its well-studied synthetic parameters and facile electrodeposition, we chose copper foams to advance DHBT materials in terms of characterization and mechanical properties. As a key step of the synthesis route, we realized a method to manufacture free-standing sheets from this material from copper metal while preserving its delicate microstructure. This was supported by an optimization of synthesis parameters to improve and ensure adequate mechanical stability of the freestanding foams after isolation. This development enables the application of a wide range of characterization methods such as XTM, BET, SEM and interferometry and I will discuss how the synthesis parameters link to the resulting material microstructure. Building on this initial success, current work focuses on the transferring this knowledge to the synthesis of foams made from other metals which are more relevant to electrochemical applications such as nickel for the use in alkaline electrolyzers and paves the way to develop DHBT material into the next generation transport layer for electrochemical systems.

Surface engineered homo-structure enabling the fast ionic conduction for ceramic fuel cells

The primary incentive for designing efficient electrolytes is to enhance the specific energy like power density, ionic conductivity, OCV (open-circuit voltage), and energy efficiency of electrochemical conversion devices. In terms of high-power efficiency, the wide bandgap semiconductor perovskite is considered a suitable candidate for fuel cell application. For example, SrTiO3 (STO) recently attracted extensive attention regarding good fuel cell performance, which can be further enhanced via surface doping. Here, we designed SCT (SrCo0.1TiO3) as an electrolyte to enable high ionic conduction via surface doping (enriched oxygen vacancies). Due to the difference in fermi-level, the space charge region can be built, which later constitutes the BIEF (Built-in electric field), enhancing the ionic conduction at the Surface of SCT. The CFC (Ceramic Fuel Cell) device using the Co-STO electrolyte delivered a maximum fuel cell performance of 782 mW/cm2 and higher ionic conductivity of 0.17 S/cm at a low operating temperature of 520 oC. DFT (Density function theory) calculation is performed to support the experimental results. The presented surface doping methodology is suitable for designing advanced materials for wide bandgap semiconductors with high ionic conductivity to develop next-generation advances for CFCs (Ceramic Fuel Cells).

Spatially Heterogeneous Chemistry Observed using NIRTI on SOFC Anodes

Solid oxide fuel cells (SOFCs) are high temperature electrochemical conversion devices which are challenging to study due to their high operating temperature and dual atmosphere requirements. Traditional tools to study SOFCs are unable to resolve any spatial dependent chemistry which may be occurring on the cell. This study used Near Infrared Thermal Imaging (NIRTI) to identify spatially varying temperature changes indicative of heterogeneous chemistry occurred during C remediation reactions using gas phase oxidants and electrochemical oxidation on anode-supported SOFCs. The spatial dependences observed are probably due to kinetics and transport of the oxidizing species involved, which may provide insight for modeling SOFC kinetics and operation.

Anthracite pretreatment for high-performance direct carbon solid oxide fuel cell — A green pathway for power generation

Coal-fueled direct carbon solid oxide fuel cell (DC-SOFC) is a very attractive electrochemical conversion device. However, coal contains a certain amount of ash, such as Al, Si, S, etc., which are toxicants for SOFC components. To solve the above problem, anthracite is pyrolyzed at 600 °C to obtain semi-coking coal results in better cell performance. The results show that the higher carbon gasification oxidation activity of semi-coking coal is due to the higher amount of fixed carbon and catalyst. Therefore, more fuel gas (CO) is available in the anode chamber for the Boudouard reaction. Also, the electrochemical performance of both coals as DC-SOFC fuel was compared using La0·4Sr0·6Co0·2Fe0·7Nb0·1O3-δ (LSCFN) as anode. The maximum power density (MPD) of the DC-SOFC with semi-coking coal is 596 mW cm−2 at 850 °C, much higher than that of the SOFC using anthracite (396 mW cm−2) as the fuel. Furthermore, at the same fuel content, the cell fueled with semi-coking coal has a longer discharge time (30 h), which shows a better stability.

Sonochemical Synthesis of Cu@Pt Bimetallic Nanoparticles.

Reducing the amount of noble metals in catalysts for electrochemical conversion devices is paramount if these devices are to be commercialized. Taking advantage of the high degree of particle property control displayed by the sonochemical method, we set out to synthesize Cu@Pt bimetallic nanocatalysts in an effort to improve the mass activity towards the hydrogen evolution reaction. At least 17 times higher mass activity was found for the carbon supported Cu@Pt bimetallic nanocatalyst (737 mA mg−1, E = ) compared to carbon supported Pt nanocatalysts prepared with the same ultrasound conditions (44 mA mg−1, E = ). The synthesis was found to proceed with the sonochemical formation of Cu and Cu2O nanoparticles with the addition of PtCl4 leading to galvanic displacement of the Cu-nanoparticles and the formation of a Pt-shell around the Cu-core.

Engineering Electrodes with Bimodal Pore Size Distributions for Next-Generation Electrochemical Devices

In many electrochemical conversion devices such as low temperature fuel cells or water electrolyzers, the transport of reactants to and products from the catalyst layer is facilitated by porous structures referred to as gas diffusion layers or porous transport layers. They bridge the gap between flow fields and catalyst layers and their mass transport capabilities become especially critical at high current density operation. Excessive accumulations of reaction products or a lack of fresh reagents stall out the electrochemical conversion resulting in reduced efficiencies or even damage to the system itself due to fuel starvation1. Thus, to realize cost-competitive electrochemical systems we must overcome the fundamental challenge of multiphase flows in which liquid and gaseous phases flow through porous structures in opposing directions.In recent years, porous electrodes have been adapted to better address these issues and improve performance. For example, the addition of a layer with reduced pore size facing the catalyst layer (i.e., micro porous layer) was shown to increase performance in fuel cells and electrolyzers2–4. Furthermore, chemical5 as well as mechanical6,7 methods of creating dedicated liquid and gas pathways in the structure have been investigated with promising results. These approaches are however intrinsically limited by the microstructure of the material they are applied to.Inspired by the success of these modifications, we propose a novel structure containing both a pore size gradient as well as dedicated water and gas pathways in the form of bimodal pore size distributions (Figure 1). This material is generated by depositing a metal in the presence of gas evolution to form a structure containing microscopic and macroscopic pores. This type of material has in the past been used successfully to improve boiling heat transfer8, another process faced with the counterflow of liquid and gas. They have also been investigated as high surface area material for microbial anodes9 and have been postulated to find application in other electrochemical devices such as batteries or fuel cells10. In this talk, I will discuss the synthetic approach to manufacture self-standing porous electrodes using an electrochemical flow platform and elucidate the correlation between applied electrochemical parameters and resulting material microstructure. Properties such as electrode thickness and pore sizes can be adjusted during the synthetic process to suit the requirements of specific applications exhibiting complex mass transport requirements.Acknowledgements:This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 899987.

(Invited) Anion Exchange Membrane and Ionomer Development for Electrochemical CO2 Reduction

Recent developments have proven the economic potential of electrochemical reduction of CO2 to value added chemicals, where single cells are now capable of achieving high energetic efficiencies at industrially relevant current densities. 1 These advances are in no small part due to the increased ionic conductivity, hydroxide stability and commercial availability of anion exchange membranes (AEMs). However, there currently exists little understanding as to how these materials affect the efficiency of CO2 conversion devices because the research community is only now beginning to understand the variety and complexity of the transport processes involved. 2 In collaboration with Ionomr Innovations Inc. and the National Research Council of Canada, and as part of the Energy for Clean Materials Challenge Program, we have made advances in the understanding of how AEM properties affect device performance and how we can develop materials tailor-made for CO2 electrolyser technology.Here, we demonstrate the development of a zero-gap single cell design, utilizing first generation Aemion® materials for the conversion of CO2 to CO with an energetic efficiency of 40% at 200 mA cm-2. 3 Despite the initially high energetic efficiency, we demonstrate how the crossover of carbonate dianions results in the reduction of anolyte pH and deconvolute how this results in a diminished cell efficiency over extended operation. From this, we show how functionalization of the polymer electrolyte structure can reduce this degradation mechanism while retaining high energetic efficiencies.In addition, we demonstrate how under milder electrolysis conditions, the total cell efficiency has a significant dependency on the flux of alkali metal cationic species from the supporting anolyte to the cathode. We show that due to the large promotion effect of cations for the electrochemical CO2 reduction, AEM design not only influences ohmic resistances in the cell, but also greatly affects the charge transfer resistance (RCT) of the cathode to a much greater extent than other electrochemical conversion devices. We thus make correlations between water permeability and perm-selectivity of AEMs to the overall CO2 conversion efficiency.We then discuss the incorporation of anion exchange ionomers in the cathode catalyst layer of CO2 electrolysis cells and how the ionomer parameters define the efficiency and selectivity of Ag catalysts towards electrochemical CO2 reduction. Through this work, we demonstrate the influencing factors of AEM and ionomer materials on the efficiency of electrochemical CO2 conversion and conclude that further advances are paramount for the adoption of this promising technology, which is integral in closing the carbon loop of the petrochemical industry and meeting our wider climate change targets.

Reconstruction optimization of distorted FeOOH/Ni hydroxide for enhanced oxygen evolution reaction

Oxygen evolution reaction (OER) is one of the most important anodic reactions in electrochemical conversion devices. Although a lot of OER electrocatalysts have been developed, the actual active sites during OER have not been fully understood. Herein, we report that the distorted FeOOH/Ni hydroxide on Ni foam (NF) (d-FeOOH/Ni hydroxide-NF) shows better electrochemical performance (1.50 V at 100 mA/cm2 and long-term stability for 32 h at 425 mA/cm2) than crystalline FeOOH/Ni hydroxide-NF (c-FeOOH/Ni hydroxide-NF) and outperforms most of the state-of-the-art electrocatalysts. By using in-situ and ex-situ techniques, we show that the interfaces in d-FeOOH/Ni hydroxide-NF, which are the key active sites for OER, are well maintained during the reaction, leading to promoted catalytic performance and long-term stability at high current density. We demonstrate that the structure rearrangement in d-FeOOH/Ni hydroxide-NF endows high flexibility of the lattice and tolerates the volume expansion during OER. Our study provides an insightful understanding on the catalytic performance of Fe-Ni-based electrocatalysts and the guidance to their design and synthesis for practical application.

Assessment of Catalyst Layer Quality By Image Processing and Correlation to Its Degradation Behavior in PEM Water Electrolysis

The large-scale use of electrochemical conversion devices, such as proton exchange water electrolysis, depends strongly on advances in the cell core.1 The design of the membrane electrode has a critical impact on performance, durability, and cost, which are mainly determined by the scarcity of the components used. Recent studies have shown that reducing the amount of iridium at the anode is the most important task while maintaining system performance and durability.2 This endeavor requires a more detailed description of the catalyst layer than is currently available to enable strategies for improved durability.3, 4 Imaging techniques, such as microscopy and X-ray tomography, are widely used but suffer from limited performance due to the current nature of their use. We demonstrate the possibility of unleashing the full power of imaging techniques by using a Python-based image processing analysis to correlate our results with the durability of the catalyst layers studied. Moreover, we present a route to quality control parameters for catalyst layers that are transferable to industrial use or other fields. Acknowledgement This project has received funding from the European Union's Horizon 2020 research and innovation programme under the PROMET-H2 grant agreement No 862253. References U. Babic, E. Nilsson, A. Pătru, T. J. Schmidt and L. Gubler, Journal of The Electrochemical Society, 2019, 166, F214-F220.S. M. Alia, K. S. Reeves, J. S. Baxter and D. A. Cullen, Journal of The Electrochemical Society, 2020, 167.O. Panchenko, M. Carmo, M. Rasinski, T. Arlt, I. Manke, M. Müller and W. Lehnert, Materials Today Energy, 2020, 16.S. Zaccarine, S. Mauger, W. McNeary, A. Weimer, S. M. Alia, M. Shviro, M. Carmo, B. S. Pivovar and S. Pylypenko, Microscopy and Microanalysis, 2020, 26, 772-774.

Electrochemical Performance of Pr0.8Ca0.2Fe0.8Co0.2O3-δ as Air Electrode for Reversible Solid Oxide Cells

Energy and environmental issues have always been topics of great concern to the world in recent years. The production of electricity from solar and wind energy has increased dramatically. These significant developments in renewable energy technologies are now driving the development of a method to efficiently store and transport the inherently intermittent electricity from these natural resources [1]. Under this situation, the emergence of reversible solid oxide cells (RSOCs) has been attracted widespread attention. As a clean and efficient electrochemical conversion device, RSOCs can link electrical and chemical energy and convert flexibly, which is of great significance for power generation and energy storage [2]. It can operate in two modes: (i) as solid oxide fuel cells (SOFCs) for power production and (ii) as solid oxide electrolysis cells (SOECs) for hydrogen and oxygen production [3].Herein, we successfully synthesized a novel perovskite Pr0.8Ca0.2Fe0.8Co0.2O3- δ and used it as an air electrode in reversible solid oxide cells. In the SOFCs mode, the peak power density is up to 1.056 W cm-2 at 850 ºC using hydrogen as the fuel and air as the oxidant. It can achieve 1.43 A cm-2 at 850 ºC under an operating voltage of 1.3 V in the SOECs mode with water content of 50%. Moreover, the cell can run stably in both SOFCs and SOECs modes with showing excellent reversibility. During a short-time reversible term, it remains both electrochemical performance and structure stable. These results demonstrate that the perovskite Pr0.8Ca0.2Fe0.8Co0.2O3- δ is promising air electrode for applications in RSOCs.

Modulation of electronic structure and oxygen vacancies of perovskites SrCoO3-δ by sulfur doping enables highly active and stable oxygen evolution reaction

Resolving the energy crisis and advancing the commercialization of electrochemical conversion devices is urgent tasks nowadays. Developing cost-effective electrocatalysts for oxygen evolution reaction (OER) is of foremost importance for these electrochemical conversion devices. Herein, we developed a non-metallic and cost-effective sulfur-doped SrCoO3-δ perovskite electrocatalyst, namely SrCoO3-xSx (x = 0.02, 0.04, 0.06, 0.08 and 0.1, denoted as SCS2, SCS4, SCS6, SCS8 and SCS10, respectively) for water splitting in alkaline solution. Sulfur doping results in a structural change of SrCoO3-δ perovskite from hexagonal to cubic perovskite. The electrochemical performance of this catalyst indicates that an optimal sulfur doping could enhance the conductivity of SrCoO3-δ, resulting in a remarkable improvement on OER activity. The DFT calculation also confirm S doping can improve the electron conduction by lowering the activation energy of electron conductivity. Moreover, the doped SrCoO3-xSx also show enhanced durability due to the stable cubic structure with sulfur substitution. This work offers an inexpensive doping strategy for SrCoO3-δ perovskite as an efficient electrocatalyst for the enhanced electrochemical performance of OER activity in water splitting.

Discovery of Quantitative Electronic Structure‐OER Activity Relationship in Metal‐Organic Framework Electrocatalysts Using an Integrated Theoretical‐Experimental Approach

AbstractDeveloping cost‐effective and high‐performance catalysts for oxygen evolution reaction (OER) is essential to improve the efficiency of electrochemical conversion devices. Unfortunately, current studies greatly depend on empirical exploration and ignore the inherent relationship between electronic structure and catalytic activity, which impedes the rational design of high‐efficiency OER catalysts. Herein, a series of bimetallic Ni‐based metal‐organic frameworks (Ni‐M‐MOFs, M = Fe, Co, Cu, Mn, and Zn) with well‐defined morphology and active sites are selected as the ideal platform to explore the electronic‐structure/catalytic‐activity relationship. By integrating density‐functional theory calculations and experimental measurements, a volcano‐shaped relationship between electronic properties (d‐band center and eg filling) and OER activity is demonstrated, in which the NiFe‐MOF with the optimized energy level and electronic structure situated closer to the volcano summit. It delivers ultra‐low overpotentials of 215 and 297 mV for 10 and 500 mA cm−2, respectively. The identified electronic‐structure/catalytic activity relationship is found to be universal for other Ni‐based MOF catalysts (e.g., Ni‐M‐BDC‐NH2, Ni‐M‐BTC, Ni‐M‐NDC, Ni‐M‐DOBDC, and Ni‐M‐PYDC). This work widens the applicability of d band center and eg filling descriptors to activity prediction of MOF‐based electrocatalysts, providing an insightful perspective to design highly efficient OER catalysts.

The Gas Diffusion Electrode Setup as Straightforward Testing Device for Proton Exchange Membrane Water Electrolyzer Catalysts.

Hydrogen production from renewable resources and its reconversion into electricity are two important pillars toward a more sustainable energy use. The efficiency and viability of these technologies heavily rely on active and stable electrocatalysts. Basic research to develop superior electrocatalysts is commonly performed in conventional electrochemical setups such as a rotating disk electrode (RDE) configuration or H-type electrochemical cells. These experiments are easy to set up; however, there is a large gap to real electrochemical conversion devices such as fuel cells or electrolyzers. To close this gap, gas diffusion electrode (GDE) setups were recently presented as a straightforward technique for testing fuel cell catalysts under more realistic conditions. Here, we demonstrate for the first time a GDE setup for measuring the oxygen evolution reaction (OER) of catalysts for proton exchange membrane water electrolyzers (PEMWEs). Using a commercially available benchmark IrO2 catalyst deposited on a carbon gas diffusion layer (GDL), it is shown that key parameters such as the OER mass activity, the activation energy, and even reasonable estimates of the exchange current density can be extracted in a realistic range of catalyst loadings for PEMWEs. It is furthermore shown that the carbon-based GDL is not only suitable for activity determination but also short-term stability testing. Alternatively, the GDL can be replaced by Ti-based porous transport layers (PTLs) typically used in commercial PEMWEs. Here a simple preparation is shown involving the hot-pressing of a Nafion membrane onto a drop-cast glycerol-based ink on a Ti-PTL.

New side-chain liquid crystalline terpolymers with anhydrous conductivity: Effect of azobenzene substitution on light response and charge transfer

We have prepared and characterised a series of side-chain liquid crystalline homopolymers and terpolymers containing different azobenzene derivatives (RAzB), sulfonic groups (2-acrylamido-2-methyl-1-propanesulfonic acid, AMPS), and methyl(methacrylate) groups (MMA), as monomeric units. We have evaluated the effect of different para-substitutes of 6-(4-azobenzene -4′-oxy)hexyl methacrylate, at the side chains, OCH3, NO2 and H, on the phase behaviour and conductivity of the new polymers. The copolymers can form smectic and nematic phases, depending on their composition, and have light responsiveness, conferred by the azobenzene chromophores. The terpolymer with methoxy terminations, MeOAzB/AMPS/MMA, exhibits the highest conductivity values of the series (10−2/10−3 S·cm−1 range) through liquid crystalline phases and with signs of decoupling from polymeric segmental motions. These materials are promising candidates to develop new light-responsive polymeric electrolytes for electrochemical conversion devices in which ionic conductivity under anhydrous conditions can be controlled by their nanostructure.

Enhanced Oxygen Evolution Activity of CoO–La0.7Sr0.3MnO3−δ Heterostructured Thin Film

The design and fabrication of highly efficient oxygen evolution reaction (OER) electrocatalysts is crucial for further development of electrochemical conversion devices. In this paper, the pulsed l...

Carbon Nanofibers Encapsulated Nickel‐Molybdenum Nanoparticles as Hydrogen Evolution Catalysts for Aqueous Zn−CO2 System

AbstractCarbon capture, utilization and storage techniques have been studied extensively to reduce atmospheric carbon dioxide. However, CO2 conversion technologies are not widely proposed due to sluggish conversion rate, high energy consumption and need for precious metals as catalysts. Therefore, novel metal‐CO2 electrochemical cell has been proposed to utilize CO2 to produce electricity and H2 gas continuously. Electrochemical hydrogen evolution reaction under neutral condition has demanded the overall device performance. Herein, we have developed non‐precious NiMo‐carbon nanofiber‐based catalyst with unique matchstick‐like morphology using low temperature CVD technique and demonstrated in aqueous Zn−CO2 system. The NiMo alloy offers excellent activity by promoting hydrogen adsorption/desorption and chemically bonded carbon nanofiber assists catalytic activity by providing charge transfer. Due to superior characteristics, NiMo‐carbon nanofiber exhibits significant HER activity (over‐potential of 268 mV at 10 mA cm‐2) in CO2‐saturated 1 M KOH and superior cell performance in aqueous Zn−CO2 system (peak power density of 25 mW cm−2). In addition, the stability of the catalysts has also been investigated using chronopotentiometry and the results have compared with commercial Pt/C catalysts. We are hopeful that the present study will provide insights into developing non‐precious electrocatalysts, particularly for metal‐CO2 electrochemical conversion devices.