Current Opinion in Electrochemistry最新文献

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.

Natural electron-conducting circuits play essential roles in respiration and photosynthesis and are therefore of fundamental importance to all life on earth. These circuits are composed of redox-active cofactors housed within proteins, or multi-subunit protein complexes, facilitating the conduction of electrons in support of transmembrane proton pumping, redox catalysis and the extracellular delivery of electrons to terminal electron acceptors. Though the natural electron-conducting circuitry can be complex, it is possible to recapitulate selected, desirable functions within minimalist de novo-designed proteins. Here we highlight recent advances in the de novo design of redox proteins and enzymes that illustrate the progress and potential of this approach, providing insight into the workings and engineering of their natural counterparts, while creating a readily adaptable and robust set of components for future bioelectronic engineering.

Self-management of health and disease control using implantable biosensors is presently evolving strongly. Implantable biosensors require high selectivity and sensitivity, robust stability, temporal resolution, and device miniaturization. Electrochemical enzymatic biosensors that utilize specifically selective enzymes to convert the concentration of biomarker metabolites into electrochemical signals hold great promise to meet these criteria. As for electrochemical enzyme biosensors in continuous glucose monitoring, which have enjoyed great commercial success, amperometric biosensors have so far dominated enzymatic biosensor research and development. Potentiometric enzymatic biosensor research is, however, emerging with increasing strength, in particular due to greater promise for miniaturization. This minireview focuses on how to empower potentiometric enzymatic biosensors with high temporal resolution for continuous in situ monitoring of metabolites using the innovative non-equilibrium approach.

Electrochemical interfaces are central to the function and performance of energy storage devices. Thus, the development of new methods to characterize these interfaces, in conjunction with electrochemical performance, is essential for bridging the existing knowledge gaps and accelerating the development of energy storage technologies. Of particular need is the ability to characterize surfaces or interfaces in a non-destructive way with adequate resolution to discern individual structural and chemical building blocks. To this end, sub-diffraction-limit low-energy infrared optical probes that exploit near-field interactions within atomic force microscopy platforms, such as pseudoheterodyne nanoimaging, photothermal nanoimaging and nanospectroscopy, and nanoscale Fourier transform infrared spectroscopy, are all powerful emerging techniques. These are capable of non-destructive surface probing and imaging at nanometer resolution. This review outlines recent efforts to characterize ex situ,in situ,andoperando electrode materials and electrochemical interfaces in rechargeable batteries with these advanced infrared near-field probes.

Flavin-based electron bifurcation (FBEB) was discovered as a significant process of microbial energy conservation less than two decades ago. Since then, several classes of enzymes engaging in FBEB have been identified, all of which utilize a flavin cofactor that accepts two electrons and then transfers one along an exergonic (high-potential) pathway and the other along an endergonic (low-potential) pathway. We describe the critical role of electrochemical techniques, especially protein-film voltammetry and spectroelectrochemistry, in determining the mechanism and energetic landscape of FBEB in a characteristic enzyme. A prospectus of future directions involving currently unutilized electrochemical techniques is discussed with regards to the salient open questions in the field of FBEB.