Dra. Elgueta-Herrera, Elizabeth

This study evaluated the stability and reusability of amino-functionalized nanocellulose aerogels as CO2-adsorbent materials. The modified aerogels, synthesized via a controlled silylation using N-[3-(trimethoxysilyl) propyl] ethylenediamine (DAMO), demonstrated excellent thermal stability up to 250 °C (TGA) and efficient CO2 adsorption through chemisorption, which was the main adsorption mechanism. The performance of the aerogels was assessed using both adsorption isotherms and the decay pressure technique, revealing that CO2 adsorption capacity increased with higher amino group loading (4.62, 9.24, and 13.87 mmol of DAMO). At 298 K and 4 bar, CO2 adsorption capacity increased proportionally with the amino group concentration, reaching values of 3.17, 5.98, and 7.86 mmol of CO2 g−1 polymer, respectively. Furthermore, over 20 adsorption/desorption cycles, the aerogels maintained 95% CO2 desorption at ambient temperature, indicating their potential for industrial use. These findings highlight the aerogels suitability as stable, reusable materials for large scale CO2 capture and storage technologies.

This review provides an overview of recent advancements in cathode materials for proton exchange membrane fuel cells (PEMFCs), focusing on their role in catalyzing the oxygen reduction reaction (ORR). This begins with a fundamental discussion of the ORR mechanism, including two‐electron and four‐electron pathways. The review then explores a wide range of electrocatalyst materials, starting with precious metal catalysts, particularly platinum‐based materials, along with alloying strategies and composite structures. This then delves into nonprecious metal catalysts, encompassing metal‐free ORR electrocatalysts, carbon‐supported composite materials (including heteroatom doping and metal‐carbon composites), and transition metal oxides. The review further examines metal phthalocyanines, biomass‐derived catalysts, bimetallic and trimetallic nanoparticles supported on carbon matrices, and chalcogenides (oxides, sulfides, and selenides) as ORR electrocatalysts. Advanced materials such as single‐ and dual‐atom catalysts, high‐entropy alloys, and metal organic frameworks derived electrocatalysts are also discussed. We analyze the identification of reaction sites and the effect of structure on catalytic activity. Furthermore, the review covers electrochemical measurements in PEMFCs and explores technological applications and industrial relevance, including products and patents. Finally, this review concludes by addressing future perspectives and challenges in the field of cathode materials for PEMFCs.

Industrialization and human activities have exacerbated water pollution, demanding effective pollutant removal methods. Bio-based hydrogels, with their high porosity and extensive surface area, hold promise for this purpose. Cellulose is a suitable biopolymer for gel fabrication; however, the adsorption capacity of unmodified raw cellulose fibers often falls short of performance expectations due to the lack of strong binding sites. Therefore, this study investigates how different cellulose fiber types, chemical treatments, and solvent systems influence hydrogel properties for adsorption applications. Hydrogels were prepared from phosphorylated and unphosphorylated unbleached kraft pulps (UKP) derived from eucalyptus and pine using NMMO and IL solvent systems. Phosphorylation increased the surface charge of UKP from ~ 0.05 to ~ 2.3 mmol/g. However, the surface charge of phosphorylated samples decreased to 0.5–0.72 mmol/g after coagulation into hydrogels. Hydrogels prepared from phosphorylated UKP exhibited superior properties compared to the unphosphorylated counterparts, including increased specific surface area (12–64 m2/g to 53–95 m2/g), swelling capacity (1930–2800% to 3400–4800%), and higher MB adsorption capacity (13–30 mg/g to 156–291 mg/g). When comparing solvent systems, the NMMO-based hydrogel showed enhanced surface area and pore characteristics, while the IL-based hydrogel exhibited increased MB adsorption capacity (291 mg/g vs. 233 mg/g). Although pine-derived hydrogels had lower MB adsorption than eucalyptus-derived ones (156 mg/g vs. 291 mg/g), both showed comparable adsorption performance for Cu2+ ions (~ 40 mg/g). Overall, the IL-derived hydrogel from phosphorylated eucalyptus UKP proved most effective for removing MB and Cu2+ from aqueous solutions. These findings contribute to advancing cellulose-based hydrogels for efficient adsorption in wastewater treatment.

Bacterial nanocellulose (BNC) is a sustainable, renewable, and eco-friendly nanomaterial, which has gained great attentions in both academic and industrial fields. Two bacterial nanocellulose-producing strains (CVV and CVN) were isolated from apple vinegar sources, presenting high 16S rRNA gene sequence similarities (96%–98%) with Komagataeibacter species. The biofilm was characterized by scanning electron microscopy (SEM), revealing the presence of rod-shaped bacteria intricately embedded in the polymeric matrix composed of nanofibers of bacterial nanocellulose. FTIR spectrum and XRD pattern additionally confirmed the characteristic chemical structure associated with this material. The yields and productivities achieved during 10 days of fermentation were compared with Komagataeibacter xylinus ATCC 53524, resulting in low levels of BNC production. However, a remarkable increase in the BNC yield was achieved for CVV (690% increase) and CVN (750% increase) strains at day 6 of the fermentation upon adding 22 mM citrate buffer into the medium. This effect is mainly attributed to the buffering capacity of the modified Yakamana medium, which allowed to maintain pH close to 4.0 until day 6, though in combination with additional factors including stimulation of the gluconeogenesis pathway and citrate assimilation as a carbon source. In addition, the productivities determined for both isolated strains (0.850 and 0.917 g L−1 d−1) compare favorably to previous works, supporting current efforts to improve fermentation performance in static cultures and the feasibility of scaling-up BNC production in these systems.

The adsorption capacity of hydrogels derived from modified xylan hemicellulose has been tested in order to develop new bio-based adsorbent materials useful for removing metal ions pollutants, such as Cd(II), Cu(II) and Pb(II) from an aqueous solution. Xylan was extracted from bleached kraft pulp of eucalyptus and subsequently modified with different proportions of functional sulfonic acid groups (HA3–HA7) and sulfonate groups (HS30–HS70) to generate hydrogels. The results showed that all the synthesized hydrogels were capable of adsorbing metal ions, being the hydrogels with 30% and 50% xylan the ones that presented the highest adsorption capacity. Maximum capacity studies at different initial concentrations revealed that at an initial concentration of 300 mg·L−1, the HA3 hydrogel presented an adsorption capacity of 193 mg Pb(II), 182 mg Cd(II), and 66 mg Cu(II) per g hydrogel. The HA5 hydrogel presented a capacity of 185 mg Pb(II), 113 mg Cd(II), and 48 mg Cu(II) per g hydrogel. The HS30 hydrogel exhibited an adsorption of 205 mg Pb(II), 174 mg Cd(II), and 71 mg Cu(II) per g hydrogel, and HS50 hydrogel exhibited an adsorption capacity of 273 mg Pb(II), 143 mg Cd(II), and 45 mg Cu(II) per g hydrogel. These results show that modified Xylan hemicellulose is a promising adsorbent for removal Cd(II), Cu(II), and Pb(II) ions from aqueous solutions.