**Abstract**

The hollow nanomaterial is a unique material to be developed because of its characteristics, especially the surface area where it has more surfaces than other materials. In general, hollow nanomaterials could be synthesized using hardtemplated, soft-templated, self-templated, template-free and simple methods. In this chance, the catalyst preparation focused on using a simple method to study its activity on the dyes photodegradation reaction, deNOx reaction, carbon dioxides utilization, and photoconversion of chemical compounds. The characterization is emphasized on Scanning electron and Transmission electron Microscopes were used to identify its structure and characteristics. Furthermore, the analysis of UV-Vis spectrophotometer and HPLC is done to point out its activity on the photodegradation of dyes, deNOx reaction, and photoconversion of cellulose and carbon dioxides utilization.

**Keywords:** simple method, hollow, nano material, spinel, perovskite

#### **1. Introduction**

Material that has space or cavity inside or not solid within is called a hollow material. The surface of hollow material has more area than regular materials. For example, a cube-shaped material (**Figure 1a**) has six surface areas, but if its shape changes to a hollow cubic structure (**Figure 1b**), so that it has eight surface areas. For instance, the surface area of the hollow cubic unit cell is 1.333 times the surface area of a regular cube per unit cell. The difference in the surface area depends on the geometric shape of the material if it is cylindrical or tubular, the difference in a surface area becomes much large.

In nature, some inorganic compounds have hollow structures such as zeolites even though the size of the hollow has not in the range of the nano category. However, the utilization of the hollow zeolite structures turned out to be quite a lot, for example, as function as molecular sieves [1], absorbents [1], and selective catalysts [2]. Although the application categories that can be covered come in microns.

In line with the development of nano and hollow materials, the manufacture of nano hollow single-crystal zeolites was carried out and shown in **Figure 2** below.

One of the applications that can be covered is the nano-sized material, such as zeolite, one of which is the molecular sieve where the application of purification

#### **Figure 1.**

*The structure area of regular and hollow cubic shapes.*

**Figure 2.**

*A flowchart and the example of Zeolite nano hollow formation [3, 4].*

or separation of pollutant particles from plastic contaminated water with nanomicrons or microbes was able to be done [5].

Based on the study of specific surface area, load capacity, material transfer as well as storage, the size of the cavity makes hollow materials have extraordinary advantages in their characteristics. Having driven by these unique characteristics, the research groups eager to explore the more possible applications such as catalysis, photocatalysis, drug delivery, solar cells, supercapacitors, lithium-ion batteries, electromagnetic wave absorption, and sensors. The challenge faced in producing hollow materials at this time is to synthesize nano hollow materials which have a series of controlled structures in terms of composition and geometric configuration so that their applicative development is still constrained. However, the progress regarding the ability to manipulate both structure and morphology of nano hollow scale solid materials will have greater control over the local chemical environment [6–9].

Furthermore, the simple method used in the manufacture of nano hollow materials emphasizes the preparation process, economic review, and environmental friendliness for each of the chemicals used. This simple method is possible to produce nano hallow materials of various shapes such as nano hollow spheres (NHS), nano hollow cubes (NHC), nano hollow squared tubes (NHST), and related fibers. The applications described are the catalytic utilization of carbon dioxide into alcohol compounds, degradation of dyes, and the conversion of nano-cellulose to alcoholic sugars by photocatalysis.
