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High-power PEMFC performance requires holistic consideration of activation, ohmic, and concentration losses. A scalable production method of ORR electrocatalysts is developed to tackle all the critical factors to achieve practical PEMFC operation.

Encapsulating platinum nanoparticles with a carbon shell can increase the stability of core platinum nanoparticles by preventing their dissolution and agglomeration. In this study, the synthesis mechanism of a platinum core-carbon shell catalyst via thermal reduction of a platinum-aniline complex was investigated to determine how the carbon shell forms and identify the key factor determining the properties of the Pt core-carbon shell catalyst. Three catalysts originating from the complexes with different platinum to carbon precursor ratios were synthesized through pyrolysis. Their structural characteristics were examined using various analysis techniques, and their electrochemical activity and stability were evaluated through half-cell and unit-cell tests. The relationship between the nitrogen to platinum ratio and structural characteristics was revealed, and the effects on the electrochemical activity and stability were discussed. The ratio of the carbon precursor to platinum was the decisive factor determining the properties of the platinum core-carbon shell catalyst.

Exposing facet and surface strain are critical factors affecting catalytic performance but unraveling the composition-dependent activity on specific facets under strain-controlled environment is still challenging due to the synthetic difficulties. Herein, we achieved a (001) facet-defined Co-Mn spinel oxide surface with different surface compositions using epitaxial growth on Co

A hierarchically porous, biaxially woven carbon nanotube sheet was proposed in a cathode of anion-exchange membrane water electrolysis to increase surface area and enhance transports.

Cell reversal is observed when a current load is applied to the polymer electrolyte membrane fuel cell under fuel starvation conditions. Cell reversal causes severe corrosion (or oxidation) of the carbon support in the anode, which leads to a decrease in overall fuel cell performance. To suppress the corrosion reaction of carbon under cell reversal conditions and to increase the durability of fuel cells, studies on anode additives are being conducted. However, studies on the effect of additives on catalysts with different platinum contents have not been conducted. In this study, 20 wt%, 40 wt%, 60 wt% commercial Pt/C catalyst was applied to the anode, and 50 cycles of cell reversal were performed. Furthermore, the performance change with and without IrO2 as an additive was observed and its effect was assessed. Changes in the morphologies of the electrodes before and after cell reversal tests were also observed using a transmission electron microscope and a scanning electron microscope. The higher the platinum content of the catalyst, the more resistant to cell reversal. In addition, the addition of IrO2 to the anode effectively prevents performance degradation due to cell reversal.

A series of oligomeric chain extender-derived AEMs (QPP-b-PSK-w-TMA) are reported for AEMFC and AEMWE. Especially, the QPP-b-PSK-3.5-TMA-based AEMFC showed the highest specific power among the state-of-the-art AEMFCs with noble metal catalysts.

A substantial amount of research effort has been directed toward the development of Pt-based catalysts with higher performance and durability than conventional polycrystalline Pt nanoparticles to achieve high-power and innovative energy conversion systems. Currently, attention has been paid toward expanding the electrochemically active surface area (ECSA) of catalysts and increase their intrinsic activity in the oxygen reduction reaction (ORR). However, despite innumerable efforts having been carried out to explore this possibility, most of these achievements have focused on the rotating disk electrode (RDE) in half-cells, and relatively few results have been adaptable to membrane electrode assemblies (MEAs) in full-cells, which is the actual operating condition of fuel cells. Thus, it is uncertain whether these advanced catalysts can be used as a substitute in practical fuel cell applications, and an improvement in the catalytic performance in real-life fuel cells is still necessary. Therefore, from a more practical and industrial point of view, the goal of this review is to compare the ORR catalyst performance and durability in half- and full-cells, providing a differentiated approach to the durability concerns in half- and full-cells, and share new perspectives for strategic designs used to induce additional performance in full-cell devices.

Nickel oxide upon free chlorine treatment has been used as a heterogeneous oxidant to eliminate aqueous organic pollutants, where oxygenation or chlorination could regenerate the oxidation capacity. In order to overcome problems associated with low regeneration efficiency and undesirable chloride ion generation, we herein investigate electrochemical regeneration for sustainable catalytic usage of the free chlorine treated nickel oxide, obviating a dosage of chemicals. Scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS) characterized drop-casted catalysts with thermal decomposition to be NiO nanoparticles with amorphous nickel oxyhydroxide shells generated by free chlorine treatment. Along with an elevated open circuit potential of the active sites (NiOx(OH)y) near 0.75 V NHE (at pH 14), the chlorination was found to enhance the electrical conductivity of the catalysts. Galvanostatic anodization at current density

Proton-exchange membrane fuel-cells (PEMFCs) are promising energy conversion devices for a renewable energy ecosystem. Developing highly active, durable, and cost-effective cathode catalysts is a significant challenge for the pervasive deployment of PEMFCs. Bio-inspired single-atom M–N–C catalysts have emerged as a promising alternative to overcome the current limitations that originate from the high cost of noble metal catalysts. In this short review, we highlight recent advances in M–N–C catalysts in terms of three notable perspectives: atomic-level understanding and design of mononuclear active sites, the effect of the porous carbon structure on the electrocatalytic performance, and improving catalytic stability. In accordance with these topics, we also suggest future directions to further enhance M–N–C catalysts for highly active and stable PEMFC performance.

We introduce a simple and easy way to functionalize the surface of various carbonaceous materials through the ultraviolet light/ozone (UV/O3) plasma where we utilize the zero-, one-, and two-dimensional carbon frameworks. In a general manner, the lamps of a UV/O3 generator create two different wavelengths (λ = 185 and 254 nm); the shorter wavelength (λ = 185 nm) dissociates the oxygen (O2) in air and the longer wavelength (λ = 254 nm) dissociates the O3 and creates the reactive and monoatomic oxygen radical, which tends to incorporate onto the defects of the carbons. By tailoring the association and dissociation of the oxygen with various forms, carbon black, carbon nanofibers, and graphite flakes, chosen as representative models for the zero-, one-, and two-dimensional carbon frameworks, their structure can be oxidized, respectively, which is known as photochemical oxidation. Various carbons have their own distinctive morphology and electron transport properties, which are applicable for the lithium-sulfur (Li-S) cell. We, here, report on the improvement of electrochemical performance of the lithium/sulfur cell through such an efficient functionalization approach.

Electrochemical energy conversion and storage are central to developing future renewable energy systems. For efficient energy utilization, both the performance and stability of electrochemical systems should be optimized in terms of the electrochemical interface. To achieve this goal, it is imperative to understand how a tailored electrode structure and electrolyte speciation can modify the electrochemical interface structure to improve its properties. However, most approaches describe the electrochemical interface in a static or frozen state. Although a simple static model has long been adopted to describe the electrochemical interface, atomic and molecular level pictures of the interface structure should be represented more dynamically to understand the key interactions. From this perspective, we highlight the importance of understanding the dynamics within an electrochemical interface in the process of designing highly functional and robust energy conversion and storage systems. For this purpose, we explore three unique classes of dynamic electrochemical interfaces: self-healing, active-site-hosted, and redox-mediated interfaces. These three cases of dynamic electrochemical interfaces focusing on active site regeneration collectively suggest that our understanding of electrochemical systems should not be limited to static models but instead expanded toward dynamic ones with close interactions between the electrode surface, dissolved active sites, soluble species, and reactants in the electrolyte. Only when we begin to comprehend the fundamentals of these dynamics through operando analyses can electrochemical conversion and storage systems be advanced to their full potential., JACS Au, 2 (10), ISSN:2691-3704

Sustainable energy-conversion and chemical-production require catalysts with high activity, durability, and product-selectivity. Metal/oxide hybrid structure has been intensively investigated to achieve promising catalytic performance, especially in neutral or alkaline electrocatalysis where water dissociation is promoted near the oxide surface for (de)protonation of intermediates. Although catalytic promise of the hybrid structure is demonstrated, it is still challenging to precisely modulate metal/oxide interfacial interactions on the nanoscale. Herein, we report an effective strategy to construct rich metal/oxide nano-interfaces on conductive carbon supports in a surfactant-free and self-terminated way. When compared to the physically mixed Pd/CeO

Recent advances in electrochemical desalination techniques have paved way for utilization of saline water. In particular, capacitive deionization (CDI) enables removal of salts with high energy efficiency and economic feasibility, while its applicability has been challenged by degradation of carbon electrodes in long-term operations. Herein, we report a thorough investigation on the surface electrochemistry of carbon electrodes and Faradaic reactions that are responsible for stability issues of CDI systems. By using bare and membrane CDI (MCDI) as model systems, we identified various electrochemical reactions of carbon electrodes with water or oxygen, with thermodynamics and kinetics governed by the electrode potential and pH. As a result, a complete overview of the Faradaic reactions taking place in CDI was constructed by tracing the physicochemical changes occurring in CDI and MCDI systems.

We report on the conformal coating of thickness-tunable multilayers directly onto the sulfur (S8) cathodes by the layer-by-layer (LbL) deposition for the significant improvement in the performances of Li–S batteries even without key additives (LiNO3) in the electrolyte. Poly(ethylene oxide) (PEO)/poly(acrylic acid) (PAA) multilayers on a single poly(allylamine hydrochloride) (PAH)/PAA priming bilayer, deposited on the S8 cathodes, effectively protected from the polysulfide leakage, while providing a Li+ ion diffusion channel. As a result, PAH/PAA/(PEO/PAA)3 multilayer-coated cathodes exhibited the highest capacity retention (806 mAh g–1) after 100 cycles at 0.5 C, as well as the high C-rate capability up to 2.0 C. Furthermore, the multilayer coating effectively mitigated the polysulfide shuttle effect in the absent of LiNO3 additives in the electrolyte.

An ideal polymer electrolyte membrane fuel cell (PEMFC) is one that continuously generates electricity as long as hydrogen and oxygen (or air) are supplied to its anode and cathode, respectively. However, internal and/or external conditions could bring about the degradation of its electrodes, which are composed of nanoparticle catalysts. Particularly, when the hydrogen supply to the anode is disrupted, a reverse voltage is generated. This phenomenon, which seriously degrades the anode catalyst, is referred to as cell reversal. To prevent its occurrence, iridium oxide (IrO2) particles were added to the anode in the membrane-electrode assembly of the PEMFC single-cells. After 100 cell reversal cycles, the single-cell voltage profiles of the anode with Pt/C only and the anodes with Pt/C and various IrO2 contents were obtained. Additionally, the cell reversal-induced degradation phenomenon was also confirmed electrochemically and physically, and the use of anodes with various IrO2 contents was also discussed.

Iron- and nitrogen-doped carbon (Fe–N–C) catalysts have received significant attention owing to their high oxygen reduction reaction (ORR) activities, which are comparable to those of state-of-the-...

In recent years, there have been growing interest in indoor air quality, and large efforts have been devoted to controlling the concentration of CO2 below a certain level. Lithium hydroxide (LiOH) is the most widely used material for CO2 capture due to its large adsorption capacity and fast kinetics; however, steep increase in the cost of lithium is endangering the economic feasibility of CO2 adsorbents comprised of LiOH. In order to resolve this problem, we herein propose an electrochemical system for selective recovery of LiOH from used CO2 adsorbents. Electrocatalytic water splitting electrodes separated by a cation exchange membrane enable selective migration of lithium ions from the oxygen-evolving feed chamber to hydrogen-evolving recovery chamber, and this leads to one-step production of LiOH solution. Electrochemical behaviors of the system, including the time-dependent quantities of the active chemical species during the operation, are discussed by experimental and theoretical investigations, and the strategy to maximize the energy efficiency of our system is suggested.

Here we report a self-supported SnO2 nanofilm prepared by a robust electrochemical process as an electrocatalyst for the CO2 reduction reaction. The SnO2 film had a large surface area originating from its nano-architecture and manifested high selectivity toward formate (over 60%), which resulted in CO2-to-formate current density up to 33.66 mA cm−2 that is among the state-of-the-art. We unveiled that the high performance of the SnO2 nanofilm is attributable to the presence of a metastable oxide under reductive conditions in addition to the abovementioned advantages.

Electrocatalysis is a key process for renewable energy conversion and fuel production in future energy systems. Various nanostructures have been investigated to optimize the electrocatalytic activity and realize efficient energy use. However, the long-term stability of electrocatalysts is also crucial for the sustainable and reliable operation of energy devices. Nanocatalysts are degraded by various processes during electrocatalysis, which causes critical performance loss. Recent

Silicon (Si) anodes in lithium-ion batteries (LIBs) suffer from huge volume changes that lead to a rapid capacity decrease and short cycle life. A conductive binder can be a key factor to overcome this issue, maintaining continuous electron paths under pulverization of Si. Herein, composites of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and poly(vinyl alcohol) (PVA) are augmented with poly(ethylene glycol) (PEG) and poly(ethylene oxide) (PEO) as a binder for Si anodes, which forms hierarchical structures due to different chain lengths of PEG and PEO. The integration of PEG and PEO imparts higher electrical conductivity (∼40%) and stretchability (∼60%) through densely spread hydrogen bonding and cross-linking, compared to conductive polymer binders with PEO or PEG. Further, a silver nanowire (AgNW) network combined with the polymer binder supplies an effective three-dimensional (3D) electrical path, sufficient void space to buffer the volume changes, and highly adhesive interaction with the current collector. The fabricated Si anode demonstrates a higher specific capacity of 1066 mAh g