Current Opinion in Electrochemistry最新文献

Fundamental insights into electrode–electrolyte interfaces are crucial for our understanding of electrochemical processes. Standard electrochemical methods, such as cyclic voltammetry, can reveal important information about the systems of interest. Nevertheless, information about structure and morphology of the electrode–electrolyte interface is not that easily accessible. In situ scanning tunnelling microscopy can resolve the electrode as well as the direct interface to the electrolyte in real time during electrochemical measurements. This includes changes of the electrode in the nanometre to micrometre range, for example, during metal deposition or corrosion, as well as the observation of ordered molecular adlayers on the electrode. In this work, we want to highlight the capabilities of such studies to better understand the fundamental processes of electrocatalysis and metal deposition and dissolution, which are essential to electrochemical energy storage systems.

The ferro-/ferricyanide couple has been extensively investigated as a redox species in various redox flow batteries (RFBs) due to its advantageous electrochemical properties, user-friendliness, and affordable cost. However, the high concentration and stability of ferro-/ferricyanide are important for developing high-energy density and long-cycle life RFBs. Different methods have been explored to increase its concentration through diverse ion effects and cation modification while also exploring the effects of pH, light, and air sensitivity on its stability. This review will provide an overview of recent research on the concentration enhancement of ferro-/ferricyanide and its stability for RFBs.

The recent integration of machine learning into materials design has revolutionized the understanding of structure–property relationships and optimization of material properties beyond the trial-and-error paradigm. On one hand, machine learning has significantly accelerated the development of atomically dispersed metal-nitrogen-carbon (M-N-C) electrocatalysts, which traditionally heavily relied on heuristic approaches. On the other hand, the primary challenge of leveraging machine learning to expedite M-N-C materials discovery lies in the cost associated with data collection. We review recent machine learning integration strategies for M-N-C catalyst development, including discussions on the typical algorithms such as symbolic regression and convolutional neural networks employed for the theoretical design, synthesis optimization via active learning, and advanced microscopy characterization. Subsequently, we provide our perspective on potential near-future directions for furthering machine learning-assisted development of new M-N-C catalysts and elucidating the complex physicochemical mechanisms governing the selectivity, activity, and durability in this class of materials.

Materials degradation is a major factor that limits the wider adoption of renewable and clean energy technologies. This is particularly true for the Pt group metal-free (PGM-free) atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts. While many experimental studies have investigated and reported the phenomenological aspects of M-N-C degradation, only a few modeling studies have considered degradation mechanisms at the atomic level. Understanding the mechanisms responsible for activity loss occurring in atomically dispersed M-N-C’s is crucial towards rationally designing active, durable, and less expensive Earth-abundant catalysts. Towards this end, we have surveyed recent literature concerning the modeling of corrosion mechanisms that impact M-N-C catalysts (Fe–N–C, in particular) and offer our own perspectives on the future direction of this field.

Coulombic efficiency (CE) is a crucial metric in battery research, particularly for aqueous Zinc (Zn)-metal batteries. Nonetheless, the accurate determination of Zn CE is complicated due to a lack of awareness about charge loss triggered by the hydrogen evolution reaction (HER) and non-standardized testing conditions. This study reveals the governing factors affecting the Zn CE measurement under different testing conditions, such as applied current density, Zn-plating capacity, and half-cell platforms. Through literature and experimental studies, it is evident that the Zn CE inherently increases with higher current densities and capacities. When decoupling the actual potentials of HER and Zn deposition, HER-triggered parasitic reactions can be self-suppressed owing to greater overpotential for HER than for Zn-plating at higher current densities. A consistent trend was observed when using different Zn salts and current collectors. This awareness can help standardize CE measuring protocols for validating novel concepts and materials.

The advancement of photocatalytic technologies requires complete system efficiency, and to this end, electrochemical sensors have the potential to complement and enhance the development of semiconductor catalyst and reactor design. A particular advantage of electroanalysis is that the sensors may be incorporated directly into photocatalytic reactors to allow real-time in situ analysis. This can then facilitate more accurate process control in the photocatalytic reactor. This report highlights the use of electroanalysis to monitor photocatalytic processes, considering applications where it has been used to date. Relevant properties of the sensors, with particular interest on sensitivity and response times are detailed alongside comparison to the more commonly used analytical techniques. It also explores the most recent progressions beyond monitoring photocatalytic remediation processes including photocatalytic valorization and reactive oxygen species monitoring.

Interfacial science and electroorganic syntheses are inextricably linked because all electrochemical reactions occur at the interface between the electrode and the solution. Thus, the surface chemistry of the electrode material impacts the organic reaction selectivity. In this short review, we highlight emergent examples of electrode surface chemistries that enable selective electroorganic synthesis in three reaction classes: (1) hydrogenation, (2) oxidation, and (3) reductive C–C bond formation between two electrophiles. We showcase the breadth of techniques, including materials and in-situ characterization, requisite to establish mechanistic schemes consistent with the observed reactivity patterns. Leveraging an electrode's unique surface chemistry will provide complementary approaches to tune the selectivity of electroorganic syntheses and unlock an electrode's catalytic properties.

This opinion addresses a basic impossibility to use Ni-containing and similar mediator electrocatalysts for fuel cell anodes if the fuel is organic, and air (or oxygen) is the oxidant. The reason is that oxidation onset potential is always higher than O₂/H₂O equilibrium potential. These anodes can operate in fuel cells with peroxide, but the voltages reported for direct urea peroxide fuel cells demonstrate contradiction with urea oxidation onset potentials. Ni-containing anodes for “boosting” in water electrolysis and in electrochemical reforming present more heathy research branch.

Flexible and wearable electronics are poised to revolutionize various domains, but the practical implementation of these devices is hindered by the significant difficulty of energy storage devices. An effective solution can be found in the advancement of high-performance supercapacitors by developing with the qualities of being integrated, elastic, and self-healable, without requiring additional film layers. Hydrogels greatly contributed to achieving this owing to their interesting properties, conductivity, and flexibility. This short review explores the recent progressions in all-in-one supercapacitors powered by hydrogels, highlighting their functional mechanisms of self-healing, ion transmission, and synchronous deformation. We discussed the potential applications in wearable electronics, medical devices, and flexible energy storage systems, focusing on design optimization and new functionalities. Furthermore, we provide insights into future research directions, guiding the exploration of novel additives and achieving high and stable performance.

Dissolved iron in alkaline media is an important topic influencing a wide array of electrochemical reactions and most notably those occurring in alkaline water electrolysers. This work compiles the study techniques and strategies that have been used in the past few years to help tackle this challenging issue. Focus is made on iron solubility in the studied medias, the importance of using a quality reference electrolyte, where and how to measure iron content in the system, and also on what is agreed and what is debated concerning the influence of dissolved iron on the hydrogen evolution reaction and oxygen evolution reaction, notably in the way these electrolyte impurities do enhance or alter the reactions kinetics.