Current Opinion in Electrochemistry最新文献

The study of single redox enzymes by electrochemistry is well-established, using both mediated and direct electron exchange between the enzyme and electrode. Moving beyond single enzymes, electrochemically driven multienzyme cascades can achieve more complex transformations, and in this review, we highlight recent advances. Electrochemical control of multiple enzymes is discussed, with examples including, electrode surface modification and engineering of the enzymes to facilitate direct electron exchange with the electrode, and new developments made by the entrapment of enzymes in a highly porous electrode called the electrochemical leaf. Examples that harness the power of direct control of the potential and the ability to monitor cascade activity as electrical current, include synthesis, deracemization, and measurement of drug binding kinetics. Redox cofactors (e.g. NADP(H)) can be electrochemically regenerated by a variety of enzymes, but non-redox cofactors are less amenable to electrochemical regeneration, and we highlight enzyme cascades for adenosine triphosphate (ATP) regeneration designed with an electrochemical step to generate the required phosphate donor. Finally, we cover approaches to model electrochemically driven cascades, which predicted local environments (e.g. pH) that are difficult to measure directly and yielded guidelines for the rational design of immobilized enzyme cascade electrodes.

The high ionic strength electrolytes stand out as promising candidates in various electrochemical applications owing to their distinct properties. These electrolytes support a variety of applications including energy devices and beyond, but involve complex interfacial structures and processes, which necessitate advanced characterization methods. Scanning probe microscopy, including atomic force microscopy and scanning tunneling microscopy, is a powerful technique with high spatial resolution and is regarded as one of the most pivotal tools for unraveling the complexities of the electrochemical interface. This review summarizes the latest advancements in surface-related scientific issues revealed by in situ scanning probe microscopic studies. The prospective applications of in situ scanning probe microscopy in the study of high ionic strength electrolytes are also briefly discussed.

Operando probing of electrochemical process and further correlation to the local structural features is a crucial route for understanding the intrinsic structure–activity relationship of electroactive materials. Scanning electrochemical cell microscopy has been proven to be a powerful and versatile tool for the in situ/operando evaluation of electrochemical activity at spatial resolution down to nanometer scale. Complementary structure characterization applied to the identical locations provides an unambiguous correlation of the intrinsic electrochemical properties to local structures. This review summarizes recent advances in this correlative approach to showcase how insightful perspectives of structure–activity relationship at the single-entity level are achieved, covering electrocatalysis, photoelectrocatalysis and energy storage. We conclude by sharing our perspective on opportunities in this field.

Electrochemical Strain Microscopy (ESM) is a technique based on Atomic Force Microscopy and provides information about local ionic processes through electro-chemo-mechanical coupling. It is employed foremost in studying battery materials, from cathodes, and anodes to solid-state electrolytes. Based on this overlap we aim to connect the electrochemistry community further with those employing ESM, by providing the current understanding of ESM, starting with a thorough introduction to the technique. In the second section, typical applications and challenges identified in recent years are reviewed while in the third chapter new approaches to overcome these issues are presented. This includes the identification of various contributions to the ESM signal, the integration of ESM as part of a multi-modal characterization approach, and importantly, how to link local ESM results to the overall cell performance in batteries. Lastly, upcoming trends and new aspects are discussed, including the application of in-situ ESM directly in an electrochemical environment.

The selective electrochemical oxidation of methane to value-added chemicals has been pursued for decades without breakthroughs and developments beyond academic research. Main setbacks encountered in virtually every report are poor methane conversion rate and selectivity. For tangible progress, research should focus on tackling CH₄ mass transport and concentration limitations. At the same time, harmonized research protocols must be developed, e.g. to define standard control experiments and key metrics. This will facilitate data comparison and accelerate electrocatalyst discovery, which so far remained challenging due to inconsistent data-reporting practices. Fundamental research on model (well-defined) electrocatalysts should also be intensified, along with in-situ spectroscopic investigations to understand the reaction mechanism and design catalysts to prevent overoxidation.

Electrospinning has emerged as a very promising preparation method of PEMFC cathode catalyst layers (CCLs) with high performance in the mass transport region due to their unique network structure for water transport and O₂ accessibility. We will present the recent improvement strategies and humidity effect for electrospun nanofiber CCLs. Additionally, we will discuss the possible causes of their humidity-dependent performance losses. Thereby, the ionomer – carrier polymer interactions and local ionomer distribution play a critical role on the proton conductivity and accessibility of active Pt nanoparticles. Despite the high current densities achieved so far, more demanding PEMFC operating strategies are required to maintain the performance of nanofiber CCLs in a wide range of humidity.

Direct seawater splitting has great potential for constructing an economic hydrogen production system and resolving water scarcity via pure water production from evolved hydrogen. However, transforming electrocatalytic direct seawater splitting into a viable process is extremely challenging from an electrocatalytic point of view. A vast number of present ions and impurities in seawater, e.g. Na⁺, Mg²⁺, Cl⁻, SO4²⁻, Br⁻, disrupts efficient oxygen evolution reaction (OER) in anode or hydrogen evolution reaction in cathode. In this respect, there are different challenges posing on understanding the effect of the complex nature of seawater especially on the OER catalysts of seawater electrolysis. This mini-review covers different electrochemical and operando techniques used in order to understand the effect of ions present in seawater on activity, stability, and the equally important reaction selectivity of OER electrocatalysts.

MXenes are a new class of two-dimensional layered structure materials that have caught attention of researchers recently. The unique feature of such a layered structure is that it can help in the easy access of electrolyte ions and offers more redox active sites, making MXenes a highly suitable electrode material for electrochemical energy storage applications, which are therefore extensively investigated in supercapacitor applications. However, for specific flexible applications, making a highly efficient flexible energy storage device with exceptional power, energy, and cycle life performance is crucial. To have high specific energy, Zn-ion-based flexible charge storage devices have been studied where MXene plays a significant role as an electrode material. However, making a flexible device with good mechanical stability along with reliable electrochemical performances is challenging. Therefore, MXene is preferred as an active material as individual, composite, and flexible film electrodes due to their high electrochemical accessibility and mechanical and electrochemical stability. Thus, this review discusses the recent developments of MXene-based Zn-ion FSC and highlights their potential for producing state-of-the-art technologies. It also discusses significant challenges and future perspectives of MXene to encourage further research and development in this area.

Zinc–sulfur (Zn–S) batteries have attracted a lot of interest in the field of battery development due to their many benefits, which include their extremely high theoretical capacity and energy density, low cost, and excellent safety. However, the development of aqueous Zn–S batteries is hampered by the slow reaction kinetics of sulphur, lower discharge voltage, cathode volume expansion during zincation, and corrosion and hydrogen precipitation reactions of the negative electrode in aqueous electrolyte. These factors also seriously affect the cycle life of Zn–S batteries. This review outlines the advancements made in the field of aqueous electrolyte modification in Zn–S batteries in recent years, emphasises the significance of optimising aqueous electrolytes in raising Zn–S battery performance, and suggests future research avenues based on the findings of the current studies.

Multiheme cytochromes (MHCs) are bacterial electron-transfer proteins. We show from optical spectra and calculations that some of these cytochromes probably contain occupied and unoccupied bands formed from heme π and π∗ orbitals that span the protein. In the fully oxidised proteins, the unoccupied π∗-bands are energetically above the redox-active frontier orbitals, which according to NMR data and calculations, are formed of Fe³⁺ t_2g and porphyrin π-orbitals. These orbitals on different hemes are electronically coupled according to EPR data and calculations, but only weakly so. We suggest a role for the heme bands in the electronic conductivity of single MHCs in bioelectronic junctions that is distinct from the role of the redox-active Fe³⁺ t_2g and porphyrin π-orbitals in physiological electron transfer.