Koray Bahadır Dönmez

A scalable, membrane-assisted electrochemical synthesis strategy is reported for the controlled production of nickel carbonate hydroxide (Ni ₂ (CO ₃ )(OH) ₂ ) using a three-compartment cell with selective ion transport across cation- and anion-exchange membranes under potentiostatic operation at 1.0 V. The catholyte and anolyte are isolated from the precipitation compartment using cation- and anion-exchange membranes, enabling selective ion transport while suppressing uncontrolled mixing and parasitic precipitation. The resulting product is structurally validated as a poorly crystalline monoclinic Ni ₂ (CO ₃ )(OH) ₂ phase, with XRD reflections consistent with low crystallinity. Raman spectroscopy further confirms carbonate incorporation via the intense ν ₁ (CO ₃ ²⁻ ) band at ∼1060 cm ⁻¹ and supports the predominance of a poorly crystalline carbonate–hydroxide framework. FTIR spectra show diagnostic hydroxyl features and carbonate modes, corroborating the targeted carbonate–hydroxide chemistry. Thermogravimetric analysis exhibits a multi-step dehydration/decomposition profile consistent with conversion of nickel carbonate hydroxide to NiO. SEM reveals hierarchical, cauliflower-like sub-micrometer agglomerates with rough, porous surfaces, while EDS supports the expected elemental composition. To validate electrochemical quality, Ni ₂ (CO ₃ )(OH) ₂ was used as the positive electrode in a Ni ₂ (CO ₃ )(OH) ₂ //activated carbon asymmetric supercapacitor employing 1 M TEATFB in acetonitrile. The device operates over a wide 0–2.5 V window and shows distinct pseudocapacitive behavior with excellent durability, retaining >80% of its initial capacity after 10,000 cycles at 5 A g ⁻¹ .

Supercapacitors have emerged as leading energy storage devices due to their remarkable capacitance, high power output and exceptional cycle life. Flexible and binder-free nanomaterials play a crucial role in improving device performance and integration. Herein, we describe the synthesis of a zinc phthalocyanine derivative, TSA–ZnPc, which incorporates thiosalicylic acid (TSA) units, and its integration with single-walled carbon nanotubes (SWCNTs) to fabricate a flexible and free-standing hybrid electrode (TSA–ZnPc–SWCNT). TSA–ZnPc was characterized by NMR, FTIR, and MALDI-TOF-MS, and its optical properties were investigated using UV-vis and fluorescence spectroscopy. The nanohybrid was assembled through noncovalent van der Waals, π–π and S–π interactions without the use of binding agents, forming smooth, interconnected SWCNT networks. This was confirmed by SEM and AFM analyses. Electrochemical measurements (CV, GCD and EIS) revealed a specific capacitance of 82.1 F g⁻¹ at 1 mV s⁻¹ with an excellent stability over 12 000 cycles, highlighting its strong potential for next-generation renewable energy-storage applications.

This study explores sustainable alternatives for supercapacitor fabrication by integrating environmentally friendly carbon materials and efficient electrode processing techniques. Traditional supercapacitors rely heavily on expensive, nonrenewable, chemically synthesized carbon nanomaterials and are typically fabricated via time‐intensive N ‐methyl‐2‐pyrrolidone (NMP)‐based slurry casting. To address these limitations, two complementary approaches are presented. First, high‐performance graphene‐like carbon is synthesized from commercial AC (YEC‐8B), using electrochemical exfoliation (EEG). Second, electrophoretic deposition (EPD) is demonstrated as a scalable method for depositing biomass‐based (derived from waste hazelnut shells) activated carbon (BAC) or composites of BAC and EEG onto nickel foam current collectors, achieving a specific capacitance of 150 F g ⁻¹ and a power density of 21 kW kg ⁻¹ . These electrodes are tested with both pure and hybrid water‐in‐salt electrolytes in A7 pouch cell supercapacitors. The pouch cell configuration that is equipped with commercially sourced composite AC and EEG electrodes shows superior capacitance retention, with 10% improvements at 10–40 A g ⁻¹ during cycling, compared to the counterparts prepared from waste biomass.

Two‐dimensional nano catalysts including graphene, reduced graphene oxide (rGO), MXene and exfoliated MXene (Exf. MXene) were synthesized and compared with commercial multiwalled carbon nanotubes (CNTs) for use in all‐vanadium redox flow batteries (VRFBs). These catalytic materials were coated onto carbon cloth (CC) and carbon paper (CP) electrodes via a horizontal binder‐free electrophoretic deposition (EPD) process. Amongst all samples, CNT‐modified CC exhibited the highest electrocatalytic activity, with improved redox kinetics and reduced charge transfer resistance, as confirmed by cyclic voltammetry and impedance spectroscopy. When tested in a flow cell at 100 mA cm ⁻² , CNT‐functionalized CC electrodes delivered ∼20% higher energy efficiency and electrolyte utilization for 200 cycles compared to pristine CC. The superior performance is attributed to the porous, conductive CNT network enabling facile electron transport. These results establish CNTs as highly effective VRFB catalysts and demonstrate EPD's promise as a scalable strategy for advanced electrode fabrication.

The hybrid electrode based on thienothiophene (TT) and single-walled carbon nanotubes (SWCNTs) exhibits a superior specific capacitance of 355.3 F g ⁻¹ as a flexible hybrid asymmetric supercapacitor after electrochemical pretreatment.

ZnO–Fe ₃ O ₄ obtained from electric arc furnace dust revealed the following properties as an asymmetric supercapacitor; C _s = 35.2 mF cm ⁻² , E = 25.03 μWh cm ⁻² , P = 430.81 μW cm ⁻² , and 81% capacitance retention after 7000 cycles.

Supercapacitors are widely accepted to be highly promising for energy storage due to their high capacitance and power density with super-long cycling stability. In addition, flexible and binder-free nanomaterials play a crucial role in supercapacitor devices and systems. Herein, we present thienothiophene (TT) and single-wall carbon nanotube (SWCNT)-based two hybrid materials, possessing triphenylamine (TPA), thiophene (Th) and EDOT moieties, i.e. TT-Th-TPA-SWCNT and TT-EDOT-TPA-SWCNT, as highly efficient supercapacitors with flexible and free-standing properties. The nanohybrids were obtained by noncovalent modifications of SWCNTs without using any binding agents. Their hybrid electrodes displayed remarkable supercapacitor performances and energy storage properties with an excellent power density of 10 000 W kg⁻¹ at 20 A g⁻¹, a maximum energy density of 5.19 ± 0.13 Wh kg⁻¹ at 0.1 A g⁻¹ and a maximum specific capacitance of 158 F g⁻¹ at 1 mV s⁻¹. Regarding the GCD results, 10 000 cycle stability was achieved with a coulombic efficiency of over 95%. These findings highlight the potential of TT and SWCNT-based hybrid materials as advanced electrodes in energy storage applications.