Progress and Perspective in harnessing MXene-carbon-based composites (0-3D): Synthesis, performance, and applications

MXene is recognized as a promising catalyst for versatile applications due to its abundant metal sites, physicochemical properties, and structural formation. This comprehensive review offers an in-depth analysis of the incorporation of carbon into MXene, resulting in the formation of MXene-carbon-based composites (MCCs). Pristine MXene exhibits numerous outstanding characteristics, such as its atomically thin 2D structure, hydrophilic surface nature, metallic electrical conductivity, and substantial specific surface area. The introduction of carbon guides the assembly of MCCs through electrostatic self-assembly, pairing positively charged carbon with negatively charged MXene. These interactions result in increased interlayer spacing, reduced ion/electron transport distances, and enhanced surface hydrophilicity. Subsequent sections delve into the synthesis methods for MCCs, focusing on MXene integrated with various carbon structures, including 0D, 1D, 2D, and 3D carbon. Comprehensive discussions explore the distinctive properties of MCCs and the unique advantages they offer in each application domain, emphasizing the contributions and advancements they bring to specific fields. Furthermore, this comprehensive review addresses the challenges encountered by MCCs across different applications. Through these analyses, the review promotes a deeper understanding of exceptional characteristics and potential applications of MCCs. Insights derived from this review can serve as guidance for future research and development efforts, promoting the widespread utilization of MCCs across a broad spectrum of disciplines and spurring future innovations.

Brazilian açaí berry seeds: an abundant waste applied in the synthesis of carbon-based acid catalysts for transesterification of low free fatty acid waste cooking oil

Residues of açaí seeds (Euterpe oleracea Mart.) were a novel source for the synthesis of the acid heterogeneous catalyst applied in the conversion of low free fatty acid waste cooking oil (WCO) to biodiesel. Yield of activated carbon (AC) and catalyst (CAT), as well as density of SO₃H groups and total acidity, was analyzed in an entirely random designed experiment using multiple linear regression, one-way ANOVA, and Tukey's post hoc test. Time, temperature, dosage of KOH, and ratio of H₂SO₄/AC were the predictor variables with 3 levels each, at a significance level of α = .05. A significant yield variation portion of AC was explained by the experimental factors (R² = .891, F (3, 23) = 62.9, p < .0001), as did the yield of CAT (R² = .960, F (3, 23) = 185.7, p < .0001), density of SO₃H (R² = .969, F (3, 23) = 242.2, p < .0001), and total acidity (R² = .973, F (3, 23) = 280.6, p < .0001). Levels of time (p = .001) and KOH dosage (p = .006) were significant to the yield of AC, and temperature levels were not influent on density of SO₃H (p = .731) or total acidity (p = .762). CAT showed a S_BET of 249 m² g^-1, V_pore of 0.104 cm³ g^-1, low crystallinity, high thermal stability, and a mesoporous amorphous structure. Optimized catalytic tests resulted in 89% conversion of WCO and 11 cycles of reuse, better than pure H₂SO₄ or pure KOH (p < .0001) and also better than many biomass-derived catalysts reported in the literature.

Growth of carbon structures on chrysotile surface for organic contaminants removal from wastewater

Amphiphilic magnetic composites were produced based on chrysotile mineral and carbon structures by chemical vapor deposition at different temperatures (600-900 °C) and cobalt as catalyst. The materials were characterized by elemental analysis, X-ray diffraction, vibrating sample magnetometry, adsorption and desorption of N2, Raman spectroscopy, scanning electronic microscopy, and thermal analysis showed an effective growth of carbon structures in all temperatures. It was observed that at 800 and 900 °C, a large amount of carbon structures are formed with fewer defects than at 600 and 700 °C, what contributes to their stability. In addition, the materials present magnetic phases that are important for their application as catalysts and adsorbents. The materials have shown to be very active to remove the oil dispersed in a real sample of emulsified wastewater from biodiesel production and to remove methylene blue by adsorption and oxidation via heterogeneous Fenton mechanism.