Current Opinion in Electrochemistry最新文献

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.

Graphene nanoribbons (GNRs) have emerged as promising candidates for catalysing the oxygen reduction reaction (ORR) due to their unique structural and electronic properties. This review presents a comprehensive overview of recent advances in utilising GNRs as catalysts or support materials for ORR application and discusses the underlying active sites, synthesis strategies, and optimisation approaches. The synergistic effects between GNRs and dopants, heteroatom substitutions and hybridisation with other materials have also been included. Moreover, experimental studies have elucidated the intricate interplay between GNR structure and the ORR kinetics, providing valuable catalyst design and optimisation insights. This review highlights the potential of GNR-based catalysts for ORR electrocatalysis and underscores the ongoing efforts to overcome existing limitations to realise their applicability in future electrochemical energy conversion technologies.

The potential for direct ethanol fuel cells (DEFCs) to provide sustainable, widely accessible power has driven development of electrocatalysts for the ethanol oxidation reaction (EOR) over several decades. However, low power output, low efficiencies, and the production of acetic acid and acetaldehyde byproducts has caused progress to stall. Consequently, interest in this area is transitioning to electrolysis of ethanol to produce green hydrogen and commodity chemicals. Concurrently, applications of DEFC as breath alcohol sensors in breathalyzers are increasing, and this has become an established commercial market for EOR catalysts. Progress in the development of these technologies has been hampered by the limited number of catalysts that have been evaluated in proton exchange membrane cells, the paucity of data on product distributions, and limited gas-phase-sensing studies.

Although alkaline water electrolysis (AWE) is a highly mature technology for hydrogen production, its potential is hindered by relatively low efficiencies at high current densities. On the other hand, to conform with “RePowerEU” directives, coupling electrolyzers with new renewable energy sources (RES) is highly demanded. However, integrating fluctuating RES poses challenges for the AWE due to increasing gas impurity as the current density decreases. Herein, we revised the most promising recent developments in materials, cell design, and system integration aimed at conquering the aforementioned challenges. It is shown that the implementation of advanced components and control strategies, e.g. electrolyte management, is vital to enhance the efficiency at high current densities and expand the load range of operation by maintaining the high gas purity.

Electron transfer (ET) and proton transfer (PT) events are involved in most of the biochemical processes in biology, such as within the aerobic respiration system and photosynthesis. Whereas most of the ET and PT reactions in biology are short-range on the (sub-)nanometer scale, several biological systems are capable of long-range ET or PT on the hundreds of nanometers to micrometers. This perspective summarizes which biological or bioinspired systems are capable of long-range ET or PT, which suggested mechanisms might explain long-range ET or PT together with the needed molecular basis within the biological material to allow this transport for very long distances. The fundamental difference between long-range ET and PT is discussed as well as design guidelines for new electron- or proton-conductive biological materials.