The Impact of Hollow Semiconductor Photocatalysts in Solar Energy Conversion to Provide Renewable and Sustainable Energy Source

By: Ivan Carlo Bonghanoy

Introduction

The straightforward and convenient circumstances for photocatalysis, where sunlight is readily available compared to other catalytic processes, it has recently been employed significantly in environmental protection and renewable energy production. Future research will pay greater attention to the properties of photocatalysts based on hollow structures with high specific surface area, high visible light absorption, and high charge separation [[1], [2], [3]]. Multiple lights can be generated inside hollow structures, increasing the effectiveness of light usage. Because hollow photocatalysts have certain qualities that can get around these difficulties, making hollow nanoscale photocatalysts is a good way to create novel, highly effective materials [4]. Hollow structures are interesting because of their inside space, which can be used to control unique photocatalytic systems [5]. The hollow catalytic material also has a large surface area, which is crucial for non-uniform photocatalyst activity.

For morphological structures in artificial photocatalytic systems, hollow structures in the field of photocatalysis are excellent [6]. First, the charge separation can be greatly improved by the nanoparticles that make up hollow photocatalysts. Reducing the size to the nanoscale scale has a significant impact on the separation of photogenerated electronhole pairs because of the high surface area, short route, and numerous active sites [7]. Nanoparticles' limited surface area, however, makes it easier for charge carriers produced by light to recombine. As a result, while minimizing their detrimental effects, nanomaterials should be fully utilized in the development of photocatalysts. Diffusion length is shortened by the porosity of hollow structures [8]. Hollow structures also have a high internal reflectivity, which helps them use light effectively and produces a lot of photogenerated charges [9].Therefore, in the development of semiconductor photocatalysis, hollow photocatalysts may be able to overcome some limitations of light adsorption and charge separation [10,11]. The hollow sphere structure has a thin shell structure and a sizable surface area [12]. The light will be refracted several times on the thin wall of the shell after entering the hollow semiconductor, increasing the light utilization rate and giving the semiconductor more energy. When the semiconductor has enough energy, the electrons in the conduction band can jump to the valence band. This indicates that the hollow structure has a high efficiency for the separation of electrons (e) and holes (h+) [13]. Many different sectors have considered hollow structural materials with a huge surface area to be highly catalytically active materials [[14],[15],[16],[17]].

Figure 1. Hollow semiconductor photocatalysts for solar energy conversion

Photocatalysts Structural Material

Due to its low density and substantial surface area, the structural material is well suited for photon mass transfer and effective use [18].The huge surface area also has a lot of surface active sites, which results in strong photocatalytic performance. Hollow semiconductor nanoparticles have demonstrated good stability in prior tests, making them appropriate for real-world uses [19]. Due to the unending supply of solar energy on which photocatalysis depends, it has recently gained popularity as an emerging technology in the field of catalysis. Researchers have employed semiconductor photocatalysis for nitrogen fixation, water breakdown, carbon dioxide reduction, and environmental management throughout the past few decades. Hydrolysis is the process of creating clean energy hydrogen from organic materials, and the environmental management side primarily comprises organic pollutant degradation and heavy metal reduction.A great number of functionalized photocatalysts are utilized in the task of environmental protection and energy generation, such as the degradation of dyes, reduction of heavy metals, and clean creation of new energy, as hollow photocatalyst synthesis technology has gradually advanced. With regard to the classification of oxides, nitrides, sulfides, and organic semiconductors (Fig. 2), case studies of photocatalytic materials, practical uses of photocatalysts to convert solar energy, the mechanism of the entire photocatalytic process, and the implications for future research into hollow materials will all be covered in-depth in this paper.

    Figure 2. Schematic of function of four common hollow nanomaterial photocatalysts

Conclusion and Outlooks

Energy and the environment, using natural light to produce energy and clean up the environment is a crucial problem. Photocatalysis based on semiconductors is a practical method for harnessing solar power. The performance of photocatalysts is restricted by the low efficiency of light absorption. As a result, a non-limiting photocatalyst that can make use of the active sites with vast surface areas of certain nanomaterials is required. Hollow objects have special qualities that can improve their capacity to absorb light. As a result, hollow semiconductor photocatalysts show promise for converting solar energy.Due to the increased specific surface area, use of solar energy, and exposure of active centers, hollow structures are undoubtedly a potent structure for enhancing energy conversion, but there are still some issues to be resolved for the synthesis and deeper understanding of hollow structured semiconductors.

 

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