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.