1-Introduction
Nanotechnology encompasses processes that manipulate matter to achieve atomic-scale sizes, leading to materials with novel properties. Advanced techniques have emerged for manufacturing highly efficient nanomaterials. Green synthesis, a simpler alternative to traditional methods, aims to reduce harsh processing conditions. This approach involves the use of bacteria, fungi, and human cells as viable systems for green synthesis [1-6]. Metal oxides are highly significant nanomaterials with versatile applications in various fields such as environment, health, and industry. Cadmium oxide, in particular, has been extensively studied and utilized. However, the toxicity of cadmium salts restricts its widespread use, despite its excellent reactivity and effectiveness in many applications. To address this issue, researchers have explored eco-friendly approaches for synthesizing cadmium oxide nanoparticles using aqueous plant extracts, providing a more sustainable and environmentally conscious method of preparation [1-3]. From plant extracts for this purpose, for example, citrus limitta peels were used to prepare cadmium oxide nanoparticles of approximately 51 nanometers and irregular shapes [7]. Agathosma betulina was also used in the preparation of this oxide in the form of irregular sphere-like structures with a size not exceeding 50 nanometers [8]. Studies remained directed for this purpose in order to obtain cadmium oxide in a regular nanoscale form, and indeed most studies have achieved this. For example, andrographis paniculata[9], green tea[10], and leucaena leucocephala[11] were used, in which the particle size ranged between 5 and 57 nm. In the pursuit of environmentally friendly alternatives and to mitigate pollution risks, our focus shifted towards utilizing cadmium oxide in hydrogen storage applications. As hydrogen plays a vital role in the new era of clean science, extensive research has been dedicated to finding cost-effective materials with superior hydrogen storage capabilities. Cadmium oxide emerges as a favorable option due to its potential. Several oxides, such as nickel oxide with added metals, have demonstrated hydrogen storage capacities of approximately 0.7 wt.%[12]. In contrast, zinc oxide exhibited a lower hydrogen storage capacity of around 1 wt.%[13]. These studies contribute to the exploration of optimal materials for hydrogen storage purposes. The pure cadmium oxide was not used until now, as only the composite Cd/CdO was used. However, the storage value reached 1.3 Wt.% [14]. Therefore, this study aims to prepare and characterize cadmium oxide nanoparticles and then complete the lack of information about the ability to store hydrogen in metal oxides.