M.Sc. Jean Gustavo de Andrade Ruthes

The efficient and selective extraction of lithium ions from aqueous media is crucial for resource recovery, yet remains challenging due to the chemical similarity of coexisting alkali ions, such as sodium. In this study, we report a two-step electrochemical strategy that utilizes tailored MXene electrodes for lithium ion extraction with enhanced selectivity and extraction rates. By preintercalating hexadecylamine (HDA) and decyltrimethylammonium (C10), which are long-chain organic molecules, into the Ti3C2Tx MXene structure, we tailored the interlayer environment to favor lithium ions over sodium ions. The HDA-intercalated MXene demonstrated high Li+/Na+ selectivity with a lithium ion uptake of 2.2 mmol/L and a suppressed sodium ion uptake (<0.2 mmol/L). Extended cycling revealed that molecular preintercalation modulates ion transport pathways and influences structural and electrochemical stability. Both HDA-Ti3C2Tx and C10-Ti3C2Tx maintained a lithium ion purity of nearly 100% over 50 cycles.

There is a need for new electrochemical energy storage materials that can handle high cycling rates (high power) for rapid charging without compromising high energy density, such as high-power Li-ion batteries (LIBs) and Li-ion capacitors (LICs). Electrically conductive and redox-active two-dimensional (2D) materials, such as transition metal carbides and borides, are promising candidates for these applications. Tailoring in-plane chemically ordered MAB phases (i-MAB) has facilitated the synthesis of their 2D derivatives (i-MBenes), which possess ordered vacancies at the metal sites. The first reported i-MBene paper is Mo4/3B2Tx, which is derived from the parent i-MAB phase (Mo2/3Y1/3)2AlB2 by the selective etching of Al and Y. In this study, we report on the synthesis of 2D Mo4/3B2Tx aerogel and its electrochemical performance as an electrode material for LIBs. Our aerogel exhibits remarkable stability during life-cycling testing at high applied specific currents, maintaining a specific capacity of 260 mAh g−1 even after completing 500 cycles under a high specific current of 2 A g−1. At a moderate specific current of 100 mA g−1, it delivers an energy density of 363 Wh kg−1, while at a high specific current of 2 A g−1, it achieves a specific power of 1300 W kg−1. Complementary density functional theory calculations further reveal that Li preferentially occupies hexagonal Mo sites in Mo4/3B2Tx, supporting the observed stable lithiation behavior and excellent high-rate capability. These results suggest that 2D Mo4/3B2Tx aerogel is a promising candidate for high-power LIBs and LICs.

Herein, we report the charge storage and plastic properties of the redox-active, bimetallic metal phosphonate framework of [Cu(2,2′-bpy)VO(O3PC6H5)2]. The flexible crystals of [Cu(2,2′-bpy)VO(O3PC6H5)2] combine high energy storage with mechanical flexibility on the same platform, which is an unusual and significant property that is not observed in traditional rigid layered electrode materials. In contrast to RuO2, graphene, or MXenes, which prefer concentrated acidic or basic electrolytes to operate effectively as electrodes, [Cu(2,2′-bpy)VO(O3PC6H5)2] operates between pH values of 4 and 10 while reaching a specific capacitance of about 140 F/g in H3PO4 at pH 4 and in NaOH at pH 10 at 1 mV/s. It also demonstrates high chemical and electrochemical stability between pH 2 and 12 and in lithium hexafluorophosphate for extended periods. The use of [Cu(2,2′-bpy)VO(O3PC6H5)2] as electrodes eliminates the need for harsh chemical environments, generating more sustainable and environmentally friendly energy storage solutions, and [Cu(2,2′-bpy)VO(O3PC6H5)2] can be synthesized in water at mild temperatures. The combination of chemical stability, mechanical flexibility of [Cu(2,2′-bpy)VO(O3PC6H5)2], and compatibility with mild electrolytes makes [Cu(2,2′-bpy)VO(O3PC6H5)2] a more sustainable alternative to conventional metal oxides, MXenes, and carbon-based electrodes in next-generation supercapacitors and battery technologies.

The demand for lithium production has seen a significant rise, with the growing electric vehicle and stationary battery markets requiring further development of sustainable and scalable extraction methods. Direct lithium extraction technologies have been developed to address potential shortages, with adsorption emerging as a key method due to its efficiency and low environmental impact. Given that Al(OH)3 is already utilized as an adsorbent in various industrial applications, the practical importance of Al-based alternative systems for lithium ion extraction is increasing, yet lithium ion recovery requires harsh chemicals. In this study, we report a novel lithium extraction method combining chemical adsorption and electrochemical release using a synthesized aluminum layered double hydroxide (Al-LDH) material, developed under mild reaction conditions. The performance of the Al-LDH electrode was evaluated against a commercial Al(OH)3 adsorbent. Comprehensive characterization using techniques such as X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy revealed detailed insights into the crystalline structure, particle size distribution, and surface morphology of the materials. The Al-LDH electrode exhibited a lithium ion adsorption capacity, achieving an average chemical uptake of lithium ions of 57.6 mg/g. In contrast, lithium-ion uptake capacity for Al(OH)3 was 1.0 mg/g over 15 cycles. Notably, this method operates under pH-neutral conditions, eliminating the need for harsh acidic or basic eluents. As a result, it prevents structural degradation and minimizes secondary pollution for potential future applications of lithium-ion recovery. The material’s layered structure selectively allowed lithium ion intake while blocking sodium ions, demonstrating its high selectivity and utility in lithium ion recovery processes. The integration of pH-neutral regeneration and high selectivity shows that Al-LDH electrodes as viable candidates for next-generation, green lithium extraction technologies.

Transition metal oxalates have been proven to be a promising electrode material for lithium-ion batteries. Here, we have designed a series of multi-phase transition metal oxalates with different structures and compositions by simply adjusting the proportions of five transition metal elements. Among them, the multi-phase mixture (MC2O4·2H2O – CuC2O4 – MC2O4·2H2O, M = Mn, Fe, Co, Ni, Cu) provides a more stable framework for the material during lithiation and delithiation, effectively alleviating the structural collapse during the cycling process. In addition, the electron transport and fast charge compensation processes of multiple electrochemically active metal pairs also contribute to the improvement of performance. Therefore, the multi-phase transition metal oxalate TMOx-2 electrode with an additional CuC2O4 phase exhibits high reversible capacity and long-term cycling stability. After 400 cycles at 100 and 500 mA/g, the specific discharge capacities are 827 mAh/g and 498 mAh/g, respectively. Constructing multi-metal, multi-phase systems by combining different transition metals enables control over potential, reaction pathways, and stability of high-performance electrodes.

Supercapacitors are efficient and versatile energy storage devices, offering remarkable power density, fast charge/discharge rates, and exceptional cycle life. As research continues to push the boundaries of their performance, electrode fabrication techniques are critical aspects influencing the overall capabilities of supercapacitors. Herein, we aim to shed light on the advantages offered by dry electrode processing for advanced supercapacitors. Notably, our study explores the performance of these electrodes in three different types of electrolytes: organic, ionic liquids, and quasi-solid states. By examining the impact of dry electrode processing on various electrode and electrolyte systems, we show valuable insights into the versatility and efficacy of this technique. The supercapacitors employing dry electrodes demonstrated significant improvements compared with conventional wet electrodes, with a lifespan extension of +45% in organic, +192% in ionic liquids, and +84% in quasi-solid electrolytes. Moreover, the increased electrode densities achievable through the dry approach directly translate to improved volumetric outputs, enhancing energy storage capacities within compact form factors. Notably, dry electrode-prepared supercapacitors outperformed their wet electrode counterparts, exhibiting a higher energy density of 6.1 Wh cm−3 compared with 4.7 Wh cm−3 at a high power density of 195 W cm−3, marking a substantial 28% energy improvement in the quasi-solid electrolyte.

In technologies for PFAS removal, one of the biggest challenges is combining high adsorption capacity with excellent regeneration capabilities. In recent years, metallopolymer-based materials have shown promising potential in both aspects. In this work, we present two convenient ways to functionalize organic microparticles with charged, functional moieties (cobaltocenium), either through a one-pot reaction via siloxane-condensation or by straightforward ring-opening reaction of epoxides. After characterization of the novel adsorbent materials by state-of-the-art analytics to verify the successful functionalization, their performance for PFAS adsorption and regeneration was investigated. To gain insight into the adsorption mechanism, experiments were first conducted at low concentrations (20 μg L−1) and in equilibrium, showing adsorption for both materials of up to 97 % for PFOA and PFOS. Furthermore, an increase in adsorption within an ionic matrix of commercial drinking water and an adsorbent preference at different pH values was demonstrated. Analysis of the influence of the concentration indicates multilayer adsorption beyond simple ion-paring, best described by a Brunauer-Emmett-Teller mechanism. Moreover, utilizing a straightforward column setup, the total PFOA capacity is analyzed, revealing a 4–5-fold increase upon functionalization, leading to 215 mg g−1 and 296 mg g−1 PFOA adsorption. Overall, column-based adsorption experiments showed promising results at low (20 μg L−1) and medium (2.25 mg L−1) PFAS concentrations. Finally, reusability and regeneration studies further revealed an excellent desorption performance upon multiple cycles and PFAS elution of up to 88 ± 4 %. © 2025 The Author(s)

The demand for lithium production has seen a significant rise, with the growing electric vehicle and stationary battery markets requiring further development of sustainable and scalable extraction methods. Direct lithium extraction technologies have been developed to address potential shortages, with adsorption emerging as a key method due to its efficiency and low environmental impact. Given that Al(OH)3 is already utilized as an adsorbent in various industrial applications, the practical importance of Al-based alternative systems for lithium ion extraction is increasing, yet lithium ion recovery requires harsh chemicals. In this study, we report a novel lithium extraction method combining chemical adsorption and electrochemical release using a synthesized aluminum layered double hydroxide (Al-LDH) material, developed under mild reaction conditions. The performance of the Al-LDH electrode was evaluated against a commercial Al(OH)3 adsorbent. Comprehensive characterization using techniques such as X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy revealed detailed insights into the crystalline structure, particle size distribution, and surface morphology of the materials. The Al-LDH electrode exhibited a lithium ion adsorption capacity, achieving an average chemical uptake of lithium ions of 57.6 mg/g. In contrast, lithium-ion uptake capacity for Al(OH)3 was 1.0 mg/g over 15 cycles. Notably, this method operates under pH-neutral conditions, eliminating the need for harsh acidic or basic eluents. As a result, it prevents structural degradation and minimizes secondary pollution for potential future applications of lithium-ion recovery. The material’s layered structure selectively allowed lithium ion intake while blocking sodium ions, demonstrating its high selectivity and utility in lithium ion recovery processes. The integration of pH-neutral regeneration and high selectivity shows that Al-LDH electrodes as viable candidates for next-generation, green lithium extraction technologies.

The demand for electronic devices that utilize lithium is steadily increasing in this rapidly advancing technological world. Obtaining high-purity lithium in an environmentally friendly way is challenging by using commercialized methods. Herein, we propose the first fuel cell system for continuous lithium-ion extraction using a lithium superionic conductor membrane and advanced electrode. The fuel cell system for extracting lithium-ion has demonstrated a twofold increase in the selectivity of Li+/Na+ while producing electricity. Our data show that the fuel cell with a titania-coated electrode achieves 95% lithium-ion purity while generating 10.23 Wh of energy per gram of lithium. Our investigation revealed that using atomic layer deposition improved the electrode's uniformity, stability, and electrocatalytic activity. After 2000 cycles determined by cyclic voltammetry, the electrode preserved its stability.

Herein, we report polyphosphonate covalent organic frameworks (COFs) constructed via P-O-P linkages. The materials are synthesized via a single-step condensation reaction of the charge-assisted hydrogen-bonded organic framework, which is constructed from phenylphosphonic acid and 5,10,15,20‐tetrakis[p‐phenylphosphonic acid]porphyrin and is formed by simply heating its hydrogen-bonded precursor without using chemical reagents. Above 210 °C, it becomes an amorphous microporous polymeric structure due to the oligomerization of P-O-P bonds, which could be shown by constant-time solid-state double-quantum 31P nuclear magnetic resonance experiments. The polyphosphonate COF exhibits good water and water vapor stability during the gas sorption measurements, and electrochemical stability in 0.5 M Na2SO4 electrolyte in water. The reported family of COFs fills a significant gap in the literature by providing stable microporous COFs suitable for use in water and electrolytes. Additionally, we provide a sustainable synthesis route for the COF synthesis. The narrow pores of the COF effectively capture CO2.