Towards the valorisation of glycerol by designing the surface chemistry of carbon xerogels by doping and oxygen functionalization.

Research on innovative approaches to the valorisation of glycerol as a subproduct of biodiesel production has acquired an increasing demand in the development of a circular economy around energy generation, especially, in the line of improvement of the heterogeneous metallic catalysts used. In this regard, carbon xerogels have gained importance due to their stability and modifiability, while transition metals such as copper stand out as a cost-effective alternative, resulting in a technology where surface engineering plays a crucial role in achieving competitive catalytic activity. Building upon this, current research evaluates doped xerogels (Si, N, or GO) as supports of Cu and catalysts by themselves for glycerol oxidation. Benefits from the incorporation of oxygenated functional groups (OFG) were also evaluated. Results showed a consistently higher selectivity towards lactic acid (LA) across all catalysts and competitive catalytic conversion. In this performance, dopants played a crucial role in surface acid-base characteristics, while oxygenated functional groups (OFG) influenced copper adsorption, dispersion, and reducibility. Notably, the Cu/CXN-f catalyst demonstrated the highest LA yield by combining the effect of N as a doping species, with the presence of OFG and the formation of appropriated metallic Cu domains. This research underscores the potential of carbon xerogels in the tailored catalyst design, contributing to sustainable chemical production through their customizable textural and chemical properties.

Reduced Graphene Oxide Aerogels Cartridges for Solid Phase Extraction of Benzotriazoles.

UV-benzotriazoles have been identified as water micropollutants that cause serious problems for human health and the environment. Their low concentration in water bodies complicates their detection by direct water analysis, slowing the corrective actions to avoid bioaccumulation. In this regard, the use of graphene-based materials with a high affinity for non-polar molecules has been demonstrated to be a potential tool for the optimal separation and concentration of this type of molecules in solid phase extraction (SPE) processes. This work evaluates the potential of novel reduced graphene oxide aerogels (rGO) as extractants of mixtures of three UV-benzotriazoles in water at low concentrations. These rGO aerogels incorporate graphenic domains into a tough structure of polymeric chains by adding graphene oxide during the synthesis of resorcinol-formaldehyde gels. Aerogels with a different content and ordering of graphenic domains were obtained and characterized using Raman, XRD, SEM and nitrogen adsorption isotherms (-196 °C). The rGO aerogels that performed better as solid phase extractants were those containing 60% rGO. Aerogels with lower rGO contents (40%) required a high-temperature (2000 °C) treatment to render competitive results. The SPE methodology using selected rGO aerogels was optimized by varying the elution solvent, elution time and volume. The best performances, i.e., recoveries of 80-100% and enrichment factors of 12.5-50, were accomplished when using 0.8 mL of tetrahydrofuran (THF) as an elution solvent. As a result, a fast (10 min) and simple extraction method of UV-benzotriazoles in water was attained, achieving a detection limit of 1 ng mL-1. Selected aerogels were finally tested for the SPE of spiked samples of river waters, showing a similar performance to that observed with synthetic mixtures.

Role of Crystalline Si and SiC Species in the Performance of Reduced Hybrid C/Si Gels as Anodes for Lithium-Ion Batteries.

In recent years, the research on lithium-ion batteries (LIBs) to improve their lifetime, efficiency and energy density has led to the use of silicon-based materials as a promising anode alternative to graphite. Specifically, crystalline silicon (cSi) and silicon carbide (SiC) obtained from deposition or reduction processes (e.g., magnesiothermal reduction) stand out for their electrochemical properties. However, the synthesis routes proposed until now have limitations that make them difficult to afford or operate on a large scale. For this reason, in this work, carbon-silicon (C-Si) hybrid materials synthesized through an efficient route are evaluated as the potential precursor for the obtention of both cSi and SiC species in a single material. The feasibility and influence of the magnesiothermal reduction process were evaluated, and materials with 10 wt.% of reduced Si and 10-26 wt.% of SiC were obtained. Both species play a role in the improvement of the performance of silicon-based materials as anodes in lithium-ion batteries. In comparison with materials obtained by the reduction of silica gels and composites, the reduced C-Si hybrid gels stand out thanks to the homogeneous distribution and stability of the species developed.

Hybrid RF-Si Xerogels: A Cost-Effective Proposal for Insulator Materials.

Hybrid xerogels RF/Si were synthesized by controlling the chemical variables involved in the polymerization process (i.e., molar ratios, dilution ratio, catalysts, etc.) and evaluated as insulator materials. Higher insulating performances were recorded for these hybrids compared with their counterparts made from only one of their components (i.e., RF or Si xerogels with similar porous characteristics). The analysis of chemical and structural features correlated with heat transfer methods was useful in understanding the sum of contributions involved in the thermal conductivity of RF/Si xerogels. Variables such as roughness and tortuosity can be used to improve the performance of xerogels from a different perspective. In this way, thermal conductivities of 25 mW/mK were achieved without lengthy process steps or special drying methods. Knowledge of material design and the use of microwave heating during the synthesis allowed us to approach a simple and cost-effective process. These results suggest that the hybrid materials developed in this work are a good starting point for the future of the massive production of insulation materials.