Cu‐based catalysts have emerged as critical components in photo‐ and electrocatalysis, offering sustainable solutions for renewable energy and environmental applications. The variable oxidation states of Cu enable diverse catalytic pathways, and its abundance, low cost, and tunable properties have positioned them at the forefront of catalytic innovation. This review provides a comprehensive overview of Cu‐based catalysts applied for sustainable energy production and environmental remediation. The classification of copper‐based catalysts, including metallic copper, copper oxides, copper sulfides, copper halide perovskites, copper‐based metal‐organic frameworks (MOFs), and covalent organic frameworks (COFs), is discussed, highlighting their structural and functional diversity. Various synthesis methods, such as wet chemical approaches, electrochemical and photochemical routes, sputtering, and thermal decomposition, are presented. The applications of copper‐based catalysts in key sustainable energy and environmental remediation processes are explored, focusing on photo‐ and electrocatalysis. Specifically, CO ₂ reduction, water splitting, oxygen reduction, nitrogen fixation, pollutant degradation, and organic synthesis are examined. The mechanisms underlying these processes are analyzed, including the factors influencing their efficiency and selectivity. These applications demonstrate their potential for tackling dual global challenges: diversifying the energy matrix and mitigating environmental issues. By bridging fundamental insights, this review underscores Cu‐based catalysts as a cornerstone in advancing sustainable energy technologies.

Nanomaterials based on metal oxides are extensively studied for several applications due to their versatility. Improvements in their performances can be obtained due to specific structural modifications. One possible modification is by doping the crystal structure, which can affect the materials structure and properties, especially in nanosized particles. Electronic features are among the properties that can be modified through the doping process, consequently morphological and optical parameters can also be controlled by this process. In this sense, this review presents some modifications to tin dioxide (SnO₂), one the most studied materials, mainly through the doping process and their impact on several properties. The article starts by describing the SnO₂ structural features and the computational models used to explain the role of the doping process on these features. Based on those models, some applications of doped SnO₂, such as photocatalytic degradation of pollutants, CO₂ reduction, and desulfurization of fossil fuels are presented and discussed. Additionally, the review describes many biological applications related to antimicrobial activity for doped SnO₂ and its nanostructures. Although most of the examples presented in this article are based on the doped SnO₂, it also presents examples related to SnO₂ composites with other nanomaterials forming heterojunctions. The metal oxides SnO₂, doped-SnO₂ and their nanostructures are promising materials, with results reported in many fields presented in this review, such as theoretical and computational chemistry, environmental remediation, nanoparticle morphology control, fossil fuels improvement, and biomedical applications. Although widely explored, there are still fields for innovation and advances with tin dioxide nanostructures, for example, in transparent conducting oxides, in forensics as materials for latent fingerprints visualization, and sensors in medicine for detection of exhaled volatile organic compounds. Therefore, this article aims to be a reference regarding correlating the doping processes and the properties presented by the SnO₂ nanostructures.

The use of ZnO as a photocatalyst for organics degradation has been reported in the literature, but a divergence of results suggests that surface groups play a critical role in its photoactivity. In this paper, we describe the influence of annealing time on the photoactivity of ZnO particles by analyzing their behavior against molecules with typically high surface adsorption, i.e., methylene blue and rhodamine B. ZnO prepared through the chemical precipitation route at room temperature has been calcined at mild temperatures to gradually eliminate surface –OH groups. Although the increase in annealing time had promoted the crystallite size to increase through the elimination of Zn(OH)₂, the particle growth reduced the specific surface area and surface hydroxylation, both of which are critical features concerning photocatalysis. The probing of the main degradation mechanisms evinced that the generation of OH* radicals is the only relevant process for oxidation, which is closely related to the nature of –OH groups. After the complete ZnO crystallization, a balance of morphology, surface area, exposed surface, and surface hydroxylation is necessary to obtain the most efficient materials.