An affordable option to Au single crystals through cathodic corrosion of a wire: Fabrication, electrochemical behavior, and applications in electrocatalysis and spectroscopy

Platinum hydride formation during cathodic corrosion in aqueous solutions

Cathodic corrosion is an electrochemical phenomenon that etches metals at moderately negative potentials. Although cathodic corrosion probably occurs by forming a metal-containing anion, such intermediate species have not yet been observed. Here, aiming to resolve this long-standing debate, our work provides such evidence through X-ray absorption spectroscopy. High-energy-resolution X-ray absorption near-edge structure experiments are used to characterize platinum nanoparticles during cathodic corrosion in 10 mol l-1 NaOH. These experiments detect minute chemical changes in the Pt during corrosion that match first-principles simulations of X-ray absorption spectra of surface platinum multilayer hydrides. Thus, this work supports the existence of hydride-like platinum during cathodic corrosion. Notably, these results provide a direct observation of these species under conditions where they are highly unstable and where prominent hydrogen bubble formation interferes with most spectroscopy methods. Therefore, this work identifies the elusive intermediate that underlies cathodic corrosion.

Electrochemical Fabrication of Nanoparticles and Single-Atom Catalysts via Cathodic Corrosion

While cathodic corrosion may appear as an undesired degradation process at electrode surfaces, it has become a powerful electrochemical method for fabricating nanoparticles and single-atom catalysts. In contrast to traditional wet chemical synthesis, cathodic corrosion affords rapid, straightforward, capping-agent-free production of nanoparticles, enabling fine control over size, shape, and elemental composition. This mini-review summarizes recent advances in cathodic corrosion-based synthesis, emphasizing its unique capabilities for producing metallic, alloyed, and oxide nanoparticles, as well as single-atom catalysts. It explores the effects of varying parameters such as electrode material, electrolyte composition, voltage waveform, and frequency on the characteristics of the generated particles. Furthermore, it highlights the enhanced electrocatalytic or photoelectrocatalytic performance of the nanoparticles produced via cathodic corrosion.

Alkali Metal Cations Induce Structural Evolution on Au(111) During Cathodic Polarization

The activity of the electrocatalytic CO2 reduction reaction (CO2RR) is substantially affected by alkali metal cations (AM+) in electrolytes, yet the underlying mechanism is still controversial. Here, we employed electrochemical scanning tunneling microscopy and in situ observed Au(111) surface roughening in AM+ electrolytes during cathodic polarization. The roughened surface is highly active for catalyzing the CO2RR due to the formation of surface low-coordinated Au atoms. The critical potential for surface roughening follows the order Cs+ > Rb+ > K+ > Na+ > Li+, and the surface proportion of roughened area decreases in the order of Cs+ > Rb+ > K+ > Na+ > Li+. Electrochemical CO2RR measurements demonstrate that the catalytic activity strongly correlates with the surface roughness. Furthermore, we found that AM+ is critical for surface roughening to occur. The results unveil the unrecognized effect of AM+ on the surface structural evolution and elucidate that the AM+-induced formation of surface high-activity sites contributes to the enhanced CO2RR in large AM+ electrolytes.

Design and characterization of an electrochemically-modulated membrane chromatography device

Membrane separations offer a compelling alternative to traditional chromatographic methods by overcoming mass transport limitations. We introduce an additional degree of freedom in modulating membrane chromatography by using metalized membranes in a potential-driven process. Investigating the impact of a gold coating on membrane characteristics, the sputtered gold layer enhances the surface conductivity with stable electrochemical behavior. However, this comes at the expense of reduced permeability, wettability, and static binding capacity (∼ 474 µg g-1 of maleic acid). The designed device displayed a homogenous flow distribution, and the membrane electrodes exhibit predominantly capacitive behavior during potential application. Modulating the electrical potential during the adsorption and desorption phase strongly influenced the binding and elution behavior of anion-exchange membranes. Switching potentials between ±1.0 V vs. Ag/AgCl induces desorption, confirming the process principle. Elution efficiency reaches up to 58 % at -1.0 V vs. Ag/AgCl in the desorption phase without any alteration of the mobile phase. Increasing the potential perturbation ranging from +1.0 V to -1.0 V vs. Ag/AgCl resulted in reduced peak width and improved elution behavior, demonstrating the feasibility of electrochemically-modulated membrane chromatography. The developed process has great potential as a gentle and sustainable separation step in the biotechnological and chemical industry.

Influence of Residual Water Traces on the Electrochemical Performance of Hydrophobic Ionic Liquids for Magnesium-Containing Electrolytes

A trace amount of water is typically unavoidable as an impurity in ionic liquids, which is a huge challenge for their application in Mg-ion batteries. Here, we employed molecular sieves of different pore diameters (3, 4, and 5 Å), to effectively remove the trace amounts of water from 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide (MPPip-TFSI) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMP-TFSI). Notably, after sieving (water content <1 mg ⋅ L-1 ), new anodic peaks arise that are attributed to the formation of different anion-cation structures induced by minimizing the influence of hydrogen bonds. Furthermore, electrochemical impedance spectroscopy (EIS) reveals that the electrolyte resistance decreases by ∼10 % for MPPip-TFSI and by ∼28 % for BMP-TFSI after sieving. The electrochemical Mg deposition/dissolution is investigated in MPPip-TFSI/tetraglyme (1 : 1)+100 mM Mg(TFSI)2 +10 mM Mg(BH4 )2 using Ag/AgCl and Mg reference electrodes. The presence of a trace amount of water leads to a considerable shift of 0.9 V vs. Mg2+/ Mg in the overpotential of Mg deposition. In contrast, drying of MPPip-TFSI enhances the reversibility of Mg deposition/dissolution and suppresses the passivation of the Mg electrode.

Surface Requirements for Optimal Biosensing with Disposable Gold Electrodes

Electrochemical biosensors are promising technologies for detection and monitoring in low-resource settings due to their potential for easy use and low-cost instrumentation. Disposable gold screen-printed electrodes (SPEs) are popular substrates for these biosensors, but necessary dopants in the ink used for their production can interfere with biosensor function and contribute to the heterogeneity of these electrodes. We recently reported an alternative disposable gold electrode made from gold leaf generated using low-cost, equipment-free fabrication. We have directly compared the surface topology, biorecognition element deposition, and functional performance of three disposable gold electrodes: our gold leaf electrodes and two commercial SPEs. Our leaf electrodes significantly outperformed the SPEs for reproducible and effective biosensing in a DNase I assay and are nearly an order of magnitude less expensive than the SPEs. Therefore, these electrodes are promising for further development as point-of-care diagnostics, especially in low-resource settings.

Structural Evolution of Pt, Au and Cu Anodes by Electrolysis up to Contact Glow Discharge Electrolysis in Alkaline Electrolytes*

Applying a voltage to metal electrodes in contact with aqueous electrolytes results in the electrolysis of water at voltages above the decomposition voltage and plasma formation in the electrolyte at much higher voltages referred to as contact glow discharge electrolysis (CGDE). While several studies explore parameters that lead to changes in the I-U characteristics in this voltage range, little is known about the evolution of the structural properties of the electrodes. Here we study this aspect on materials essential to electrocatalysis, namely Pt, Au, and Cu. The stationary I-U characteristics are almost identical for all electrodes. Detailed structural characterization by optical microscopy, scanning electron microscopy, and electrochemical approaches reveal that Pt is stable during electrolysis and CGDE, while Au and Cu exhibit a voltage-dependent oxide formation. More importantly, oxides are reduced when the Au and Cu electrodes are kept in the electrolysis solution after electrolysis. We suspect that H2 O2 (formed during electrolysis) is responsible for the oxide reduction. The reduced oxides (which are also accessible via electrochemical reduction) form a porous film, representing a possible new class of materials in energy storage and conversion studies.