Heterogeneous Catalysis

     Heterogeneous catalysis is one of the pillars of modern industrial and environmental chemistry, based on the use of a solid catalyst in contact with reactants in the gas or liquid phase. In this type of system, reactions occur on the surface of the solid, at specific regions called active sites, where reactant molecules are adsorbed, activated, and converted into products. Therefore, catalytic efficiency is directly related to the surface properties of the material, such as specific surface area, porosity, pore accessibility, and the chemical nature of surface functional groups, which control both adsorption and the desorption step of the products.

     Heterogeneous catalysis is essential in numerous industrial and environmental processes, including the synthesis of fuels and chemical products, hydrogenation and oxidation reactions, hydrocarbon reforming, CO₂ conversion, and pollutant degradation. It can also take different forms depending on the energy source used to activate the reactions. In addition to classical thermal catalysis, important approaches include electrocatalysis, in which reactions are driven and accelerated by charge transfer at an electrode/electrolyte interface; photocatalysis, where light energy generates charge carriers capable of promoting chemical reactions; and photoelectrocatalysis, which simultaneously combines light and electrical potential to enhance the efficiency, selectivity, and stability of the process. Thus, understanding heterogeneous catalysis largely means understanding how solid surfaces control chemical reactivity, making surface physical chemistry a fundamental basis for the development of more efficient, selective, and sustainable catalysts.

     Within this context, activated carbons stand out as highly versatile catalytic supports, as they exhibit a large surface area and a complex porous network capable of concentrating reactants and facilitating diffusion into the internal regions of the solid. In addition, their surfaces can be modified through chemical or thermal treatments, allowing the adjustment of polarity, acidity/basicity, and affinity toward different chemical species. These characteristics make activated carbons particularly effective for applications in catalytic processes and hybrid systems that combine adsorption and contaminant degradation.

       One of the most important roles of activated carbon in heterogeneous catalysis is to act as a support for dispersing the active phase, such as metal oxides, nanoparticles, or anchored catalytic species. By distributing the active phase in a highly dispersed manner across the surface and within the pores, the support significantly increases the number of exposed catalytic sites, reducing particle agglomeration and maximizing catalytic efficiency per mass of catalyst. In practical terms, this results in higher catalytic activity, better utilization of the metal or oxide employed, and often greater operational stability, since the porous carbon structure can help control sintering and loss of active surface area. Consequently, the combination of high surface area, tunable porosity, and surface chemistry makes activated carbons strategic supports for the development of more efficient, sustainable catalysts applicable to a wide range of chemical and environmental processes.