Electrochemical science advances最新文献

Porous membranes have emerged as promising platforms for bioanalysis because of their unique properties including high surface area, selective permeability, and compatibility with electrochemical techniques. This minireview presents an overview of the development and applications of porous membrane-based electrochemical systems for bioanalysis. First, we discuss the existing fabrication methods for porous membranes. Next, we summarize electrochemical detection strategies for bioanalysis using porous membranes. Electrochemical biosensors and cell chips fabricated from porous membranes are discussed as well. Furthermore, porous micro-/nanoneedle devices for bioapplications are described. Finally, the utilization of scanning electrochemical microscopy for cell analysis on porous membranes and electrochemiluminescence sensors is demonstrated. Future perspectives of the described membrane detection strategies and devices are outlined in each section. This work can help enhance the performance of porous membrane-based electrochemical systems and expand the range of their potential applications.

Porous membranes have emerged as promising platforms for bioanalysis because of their unique properties including high surface area, selective permeability, and compatibility with electrochemical techniques. This minireview presents an overview of the development and applications of porous membrane-based electrochemical systems for bioanalysis. First, we discuss the existing fabrication methods for porous membranes. Next, we summarize electrochemical detection strategies for bioanalysis using porous membranes. Electrochemical biosensors and cell chips fabricated from porous membranes are discussed as well. Furthermore, porous micro-/nanoneedle devices for bioapplications are described. Finally, the utilization of scanning electrochemical microscopy for cell analysis on porous membranes and electrochemiluminescence sensors is demonstrated. Future perspectives of the described membrane detection strategies and devices are outlined in each section. This work can help enhance the performance of porous membrane-based electrochemical systems and expand the range of their potential applications.

The general concept of fuel cells starts from the experiments of British physicist William Grove who published the first results on fuel cells in 1839. He used hydrogen and oxygen as a fuel and oxidizer, respectively, reacting on platinum catalytic electrodes and generating electric power. However, his research was considered only as scientific proof of the process reversed to the water electrolysis with no practical importance. Indeed, the cell invented by Grove produced a very small current and voltage over a short time. Obviously, after the concept demonstration, some engineering had to be done for improving the cell efficiency to make it feasible for practical use.

During the late 1880s, two British chemists, Ludwig Mond and his assistant Carl Langer (Figure 1), developed a fuel cell with a longer service life with improved geometry of the catalytic electrodes and flow channels (Figure 2). They used the known scientific concept from Grove's cell, but with the improved engineering. Their fuel cell generated 6 amps per square foot current density and 730 mV voltage. The cell operated with coal-derived gas as a fuel and air (actually oxygen in the air) as an oxidizer. The cell was filled with diluted sulfuric acid and included thin perforated platinum electrodes separated with a porous nonconducting membrane. The first engineered fuel cell was demonstrated and patented in 1889. Note that Ludwig Mond and Carl Langer were the first to introduce the term “fuel cell” which is commonly used now.

The author declares that he has no conflict of interest.

John Alfred Valentine Butler was the first to connect the kinetic electrochemistry built up in the second half of the twentieth century with the thermodynamic electrochemistry that dominated the first half. John Alfred Valentine Butler had, to his credit, not only the first exponential relation between current and potential (1924) but also (along with R.W. Gurney) the introduction of energy-level thinking into electrochemistry (1951).

However, Butler was not alone in this study and therefore it is necessary to give credit also to Max Volmer, a great German surface chemist, and his student (at that time) Erdey-Gruz. Butler's very early contribution in 1924 and the Erdey-Gruz and Volmer contribution in 1930 form the basis of phenomenological kinetic electrochemistry. The resulting famous Butler-Volmer equation is very important in electrochemistry.

The author declares no conflict of interest.

Supercapacitors are at the forefront of energy storage devices due to their ability to fulfill quick power requirements. However, safety and cost are important parameters for their real-world applications. Green materials-based electrodes and electrolytes can make them safer and cost-effective. Herein, a supercapacitor based on a methyl-grafted natural rubber/salt-based electrolyte and natural graphite (NG)-based electrodes are fabricated and characterized. Zinc trifluoromethanesulfonate [Zn(CF₃SO₃)₂] is used as the salt for the electrolyte. A mixture of NG, activated charcoal, and polyvinylidenefluoride is used for electrodes. Our supercapacitor shows a single electrode specific capacitance, C_sc of 4.2 Fg⁻¹ from impedance measurement. Moreover, the capacitive and resistive features are dominant at low and high frequencies, respectively. The cyclic voltammetry test shows the dependence of C_sc on the scan rate with a high value at slow scan rates. Performance of the supercapacitor during 5000 charge and discharge cycles at a constant current of 90 μA shows a rapid decrease of single electrode specific discharge capacitance at the beginning, but it starts to stabilize after about 2500 cycles. These findings are relevant to further developments of green materials-based supercapacitors, offering opportunities to expand the functionalities of supercapacitors in green technologies.

Electrochemical CO₂ reduction is a potentially up-coming technology to convert anthropogenic emitted CO₂ into chemical feedstock. Due to alkaline operating conditions of CO₂-electrolyis in gas diffusion electrodes, exothermal hydroxide ion neutralization with the excess of supplied CO₂ leads to unavoidable electricity-to-heat conversion at the cathode, therefore limiting electrical energy input efficiency. The decomposition reaction of carbonates by protons from water oxidation completes the inherent CO₂ transport at the anode. In this work, different production routes to CO are thermodynamically examined and experimentally validated. Using formic acid as an intermediate towards CO the electrical energy input efficiency can rise to 71% on a thermodynamical basis. Additionally, the possibility of altering the mechanism of CO₂ reduction under acidic conditions is investigated, which would lead to even larger electrical energy input efficiencies. The concept was investigated by pH series measurements (pH = 0–6) at 50 mA/cm² where Pb derived from Pb₃O₄ was used as a CO₂ reduction catalyst. The reduction to formic acid under acidic bulk electrolyte pH is stable at FE_HCOOH = 70% down to pH $�\approx$ 1, while HER is becoming dominant below. Even under such acidic bulk electrolyte conditions no change in reduction mechanism could be forced, which is reflected in invariant cell voltages in the model experiment.

Hydrogen evolution and oxidation reactions (HER/HOR) are the most fundamental reactions in electrocatalysis. Despite the practical significance, the mechanisms of HER/HOR in aqueous solutions are still elusive. Various theories have been proposed to rationalize the pH effect, cation effect, and structure effect of HER/HOR but none of them can explain all observations. In this review, we discuss four schools of thought for the HER/HOR, focusing on the strengths and shortcomings of each hypothesis and highlighting the magnitude of electrochemical interface structure in hydrogen electrocatalysis.

Ionic liquids (ILs) have emerged as promising biomaterials for enhancing drug delivery by functionalizing polymeric nanoparticles (NPs). Despite the biocompatibility and biofunctionalization they confer upon the NPs, little is understood regarding the degree in which non-covalent interactions, particularly hydrogen bonding and electrostatic interactions, govern IL-NP supramolecular assembly. Herein, we use salt (0-1 M sodium sulfate) and acid (0.25 M hydrochloric acid at pH 4.8) titrations to disrupt IL-functionalized nanoassembly for four different polymeric platforms during synthesis. Through quantitative ¹H-nuclear magnetic resonance spectroscopy and dynamic light scattering, we demonstrate that the driving force of choline trans-2-hexenoate (CA2HA 1:1) IL assembly varies with either hydrogen bonding or electrostatics dominating, depending on the structure of the polymeric platform. In particular, the covalently bound or branched 50:50 block co-polymer systems (diblock PEG-PLGA [DPP] and polycaprolactone [PCl]-poly[amidoamine] amine-based linear-dendritic block co-polymer) are predominantly affected by hydrogen bonding disruption. In contrast, a purely linear block co-polymer system (carboxylic acid terminated poly[lactic-co-glycolic acid]) necessitates both electrostatics and hydrogen bonding to assemble with IL and a two-component electrostatically bound system (electrostatic PEG-PLGA [EPP]) favors hydrogen-bonding with electrostatics serving as a secondary role.

The electrochemical performance of cathode materials in Li-ion batteries is reflected in macroscopic observables such as the capacity, the voltage, and the state of charge (SOC). However, the physical origin of performance parameters are atomistic processes that scale up to a macroscopic picture. Thus, revealing the function and failure of electrochemical devices requires a multiscale (and -time) approach using spectroscopic and microscopic techniques. In this work, we combine near-edge X-ray absorption fine structure spectroscopy (NEXAFS) to determine the chemical binding state of transition metals in LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622), electrochemical strain microscopy to understand the Li-ion mobility in such materials, and nanoindentation to relate the mechanical properties exhibited by the material to the chemical state and ion mobility. Strikingly, a clear correlation between the chemical binding, the mechanical properties, and the Li-ion mobility is found. Thereby, the significant relation of chemo-mechanical properties of NCM622 on a local and global scale is clearly demonstrated.