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1. High-Capacitance Gold Nanoparticles from Rhus coriaria: Green Synthesis, Characterization and Electrochemical Evaluation for Supercapacitor Technologies

   https://doi.org/10.3390/mi17010082  

   Baran, Mehmet Firat; Huseynov, Elchin; Eftekhari, Aziz; Levent, Abdulkadir; Ertaş, Erdal; Kavetskyy, Taras; Šauša, Ondrej; Katz, Evgeny; Smutok, Oleh (January 2026, Micromachines)

   The structural and electrochemical properties of gold nanoparticles biosynthesized from Rhus coriaria L. (Rc@AuNPs) were comprehensively investigated and characterized. R. coriaria (sumac) served as a natural gold reducing and capping agent due to its rich polyphenolic and phytochemical composition, enabling the sustainable, low-cost, and environmentally friendly synthesis of Rc@AuNPs. The electrochemical behavior of the hybrid material was evaluated using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). Rc@AuNPs exhibited specific capacitances of 129.48 F/g, 156.32 F/g, and 280.37 F/g in H2SO4, Na2SO4, and KOH electrolytes, respectively, indicating strong potential for supercapacitor and energy-storage applications. GCD analysis further showed Csp values of 107.69 F/g (H2SO4), 133.23 F/g (Na2SO4), and 348.34 F/g (KOH), confirming the highest charge-storage performance in basic media. EIS measurements supported these results, yielding equivalent series resistance (ESR) values of 67.96 Ω in H2SO4, 64.42 Ω in Na2SO4, and a notably lower 24.43 Ω in KOH, consistent with its higher ionic conductivity and more efficient charge transfer. Overall, the superior Csp and low ESR observed in KOH demonstrate the excellent capacitive behavior of Rc@AuNPs. These biosynthesized gold nanoparticles represent a promising and sustainable electrode material for high-performance energy-storage technologies. 

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2. The Synergetic Ionic and Electronic Features of MAPbI₃ Perovskite Films Revealed by Electrochemical Impedance Spectroscopy

   https://doi.org/10.1002/adom.202301677  

   Jha, Sauraj; Haroldson, Ross; Zakhidov, Anvar A.; Slinker, Jason D. (November 2023, Advanced Optical Materials)

   Abstract Perovskites have emerged as a forerunner of electronics research due to their vast potential for optoelectronic applications. The numerous combinations of constituent ions and the potential for doping of perovskites lead to a high demand to track the underlying electronic properties. Solution‐based electrochemistry is particularly promising for detailed and facile assessment of perovskites. Here, electrochemical impedance spectroscopy (EIS) of methylammonium lead iodide (MAPbI₃) thin films is performed and model them with an equivalent circuit that accounts for solvent, ionic, and thin film effects. A dielectric constant consistent with prior AC studies and a diffusion constant harmonious with cation motion in MAPbI₃are extracted. An electrical double layer thickness in the perovskite film of 54 nm is obtained, consistent with lithium doping in perovskite films. Comparing the EIS and equivalent circuit model of perovskite films to control ITO‐only data enabled the assignment of the ions at each interface. This comparison implied a double layer of primarily lithium ions inside the perovskite film at the solution interface with significant recombination of ions on the solution side of the interface. This demonstrates EIS as a powerful tool for studying the fundamental charge accumulation and transport processes in perovskite thin films. 

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3. Electrochemistry at single molecule occupancy in nanopore-confined recessed ring-disk electrode arrays

   https://doi.org/10.1039/C6FD00062B  

   Fu, Kaiyu; Han, Donghoon; Ma, Chaoxiong; Bohn, Paul W. (January 2016, Faraday Discuss.)

   Electrochemical reactions at nanoscale structures possess unique characteristics, e.g. fast mass transport, high signal-to-noise ratio at low concentration, and insignificant ohmic losses even at low electrolyte concentrations. These properties motivate the fabrication of high density, laterally ordered arrays of nanopores, embedding vertically stacked metal–insulator–metal electrode structures and exhibiting precisely controlled pore size and interpore spacing for use in redox cycling. These nanoscale recessed ring-disk electrode (RRDE) arrays exhibit current amplification factors, AF RC , as large as 55-fold with Ru(NH 3 ) 6 2/3+ , indicative of capture efficiencies at the top and bottom electrodes, Φ t,b , exceeding 99%. Finite element simulations performed to investigate the concentration distribution of redox species and to assess operating characteristics are in excellent agreement with experiment. AF RC increases as the pore diameter, at constant pore spacing, increases in the range 200–500 nm and as the pore spacing, at constant pore diameter, decreases in the range 1000–460 nm. Optimized nanoscale RRDE arrays exhibit a linear current response with concentration ranging from 0.1 μM to 10 mM and a small capacitive current with scan rate up to 100 V s −1 . At the lowest concentrations, the average pore occupancy is 〈 n 〉 ∼ 0.13 molecule establishing productive electrochemical signals at occupancies at and below the single molecule level in these nanoscale RRDE arrays. 

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4. Cycling Performance and Structure Evolution of Co-Free Lithium- and Manganese-Rich Layered Oxides in Lithium-Ion Batteries

   https://doi.org/10.1149/1945-7111/ae2890  

   Badami, Pavan P; Kwok, Chun Yuen; Gargye, Avi; Trask, Stephen E; Dogan, Fulya; Lopez, Antonio T; Croy, Jason R; Balasubramanian, M; Abraham, Daniel P (December 2025, Journal of The Electrochemical Society)

   Lithium- and manganese-rich (LMR) layered oxides are high-capacity cathode materials that are being considered for electric vehicle (EV) lithium-ion batteries (LIBs). Here, we investigate the electrochemical cycling behavior of cells containing a cobalt-free LMR oxide, 0.3Li₂MnO₃·0.7LiMn_0.5Ni_0.5O₂, paired with either Li or graphite anodes. Two- and three-electrode cells are cycled under varying conditions to examine the effects of oxide activation, upper cutoff voltage, separator type, and electrolyte composition. Post-cycling characterization of harvested electrodes, with electrochemical, X-ray absorption spectroscopy, and solid-state⁶Li nuclear magnetic resonance spectroscopy techniques, are used to correlate cell performance changes with redox state evolution in the oxide and Li inventory shifts in the cell. Our results show that capacity fade and impedance rise primarily originate at the graphite anode and LMR cathode, respectively. Notably, while Ni undergoes reversible redox, Mn shows no evidence of bulk redox activity even in highly-aged electrodes: only relithiated LMR electrodes show some reduction of Mn. Graphite electrodes degrade due to particle isolation and SEI growth, exacerbated by Mn dissolution and deposition on graphite anodes. These findings highlight the coupled structural and electrochemical degradation mechanisms in LMR/graphite cells and underscore lithium inventory retention and electrode interfacial stability as critical factors for enhancing long-term performance. 

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5. Ultra-thin inorganic oxide and nitride films as an alternative blocking layer for electrochemical sensors

   https://doi.org/10.1016/j.tsf.2025.140712  

   McHenry, Adam; Jolly, Grant; Young, Thomas; Brothers, Michael; Coyle, Victoria; Kim, Steve; Heikenfeld, Jason (August 2025, Thin Solid Films)

   The desire to translate biosensors for real time molecular monitoring has intensified due to the commercial success of 2-week continuous glucose monitors. However, a common limitation for emerging biosensors is that their lifetimes are often too short for commercially expected benchmarks of at least 3-day and ideally 2-week operation. Electrochemical sensors remain the preferred format of biochemical sensing thanks to their low cost, size, weight, and power requirements for mobile deployment. When exposed to biological fluid, all electrochemical sensors require a blocking layer to protect the electrode surface from fouling and redox interferents. Traditional blocking layer approaches rely on self-assembled monolayers which are often fragile to biological interferents like proteins and require specific electrode materials to improve their stability. Presented here is an evaluation of ultra-thin inorganic oxide and nitride films as an alternative to self-assembled monolayer blocking layers. Specifically, silicon oxide, silicon nitride, and aluminum oxide films were deposited by electron beam evaporation or atomic layer deposition at thicknesses of several nanometers to mimic the electrical capacitance of a conventional monolayer blocking layer. These oxide films were characterized over 7-days and demonstrated to provide poor protection against interfering redox currents from dissolved ferricyanide (150 - 300 µA/cm2) and oxygen reduction interference (30 - 60 µA/cm2). The oxide films were then used as a blocking layer in an electrochemical aptamer sensor using the previously published aptamer for phenylalanine. The phenylalanine sensor showed a binding affinity stronger than found in literature, but a reduced signal gain (∼ 20 % change in methylene blue redox current compared to the expected 50 % previously published on gold). It is speculated and supported by literature that these oxide and nitride films gradually dissolve over periods of days in an aqueous environment. Results further show that if lower quality oxide or nitride films are used, they may be more stable, but at the cost of initially higher in currents. While oxide and nitride films fail to improve upon the performance of thiol-blocking layers on gold electrodes, they may provide utility in some applications by allowing for alternate electrode materials and surfaces to be used instead of traditional self-assembled monolayers on gold electrodes. 

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