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.

Mechanochemical activation, by means of high-energy ball milling, was applied to CeO₂ as a strategy to enhance its physicochemical properties. Different milling times were screened to evaluate their effect on ceria. The fluorite-type structure of cerianite was maintained in all cases, no matter the amount of energy introduced by the milling process, as observed via X-ray diffraction (XRD). A decrease in crystallite sizes and a consequent increase in specific surface area (S_BET) were observed through XRD and N₂ sorption (BET method). Pore diameters and total pore volumes were also in line with the duration of CeO₂ milling. Moreover, redox properties and oxygen mobility studied through H₂ temperature-programmed reduction (H₂- TPR) showed an increase in reducibility with milling time, including signals of both bulk and surface ceria, due to the greater number of defects and/or oxygen vacancies achieved by mechanochemical activation. The obtained features could play an essential role in terms of metal–support interaction, reactant adsorption and/or oxygen supply during catalytic reactions. Thus, high-energy ball milling is a useful, simple and green method for the design of materials with catalytic applications.

How important is the support during the rational design of a catalyst? Herein, doped ceria (Zr; Pr and Tb) was used as an active support to prepare Pt catalysts (0.5 wt%) for glycerol selective oxidation. A thorough characterization of achieved catalytic systems showed that the nature of doping elements led to different physicochemical properties. The presence of surface Pr³⁺ and Tb³⁺ not only increased oxygen vacancies but also electron mobility, modifying the oxidation state of platinum particles. The redox properties of the catalyst were also affected, achieving a close interaction between the support and metal particles even in the form of Pt-O-Pr(Tb) solid solutions. Furthermore, the combination of medium-sized metal particle dispersion, strong metal–support interaction and a synergy between the amount of oxygen vacancies and Pt⁰, observed in the Pt/CeTb catalyst, led to a high turnover frequency (TOF) and increased selectivity to glyceric acid. Thus, the present study reveals how a simple structural modification of active supports, such as cerium oxide, by means of doping elements is capable of improving the catalytic performance during glycerol selective oxidation, avoiding the cumbersome methods of synthesis and activation treatments.

Two sets of commercial activated carbon (AC) were surface functionalized by an acid treatment using a) strong acid HNO₃ (AC80 and AC90) and b) a weak acid C₆H₈O₇ (ACC). The effect of the functionalization on the surface chemistry and structure of the AC samples was studied by means of TGA-DSC, XRD, FT-IR, N₂ adsorption, and TPD and tested in the decomposition of isopropanol. The catalysts were synthesized by the deposition of copper using a recirculation impregnation method. Metal dispersion, average size of metallic domains and metal-support interactions were correlated with the surface functionalization by using XRD, S_BET, SEM-EDS, AAS and N₂O dissociative adsorption. The acid treatments showed no effect on the crystal structure; however, increments in the acid/basic site concentration and the surface oxygen-containing functional group (OFG) content were observed, mainly in the AC80 and AC90 samples. BET surface measurements show a small decrease due to OFGs and/or copper incorporation. Copper distribution was uniform and its content shows a direct correlation with the OFG concentration. XRD reveals the presence of Cu° and Cu₂O in the Cu/AC80 and Cu/AC90 samples, possibly associated with an auto-reduction process assisted by the OFGs near the metallic centers. Cu/AC and Cu/ACC XRD patterns show no evidence of copper phases, due to low content and high dispersion. The HNO₃-treated supports showed the higher dispersions and the smallest metallic domain sizes (30%—3.3 nm Cu/AC80 and 22%—4.5 nm Cu/AC90), while Cu/ACC showed a 17% dispersion and an average metallic domain size of 5.8 nm. The presence of surface OFGs promotes selective adsorption of Cu, an increase in metal dispersion, a decrease of domain size and the presence of alternative copper-derived phases, showing increased metal-support interactions.