ABSTRACT
Photocatalysis has demonstrated the potential to solve challenges in various practical application fields such as energy and environmental science due to its environmental friendliness. However, the photocatalytic activity is mainly affected by the weak absorption of visible light and the low separation efficiency of photogenerated carriers. Herein, an S-doped g-C3N4/Bi5O7I heterojunction was designed by the calcination method. It was found that S doping not only reduces the band gap of g-C3N4, which raises the optical absorption boundary of g-C3N4 from 465 nm to 550 nm. At the same time, the introduction of S elements leads to new doping energy levels, which can act as photogenerated electron trapping centers and thus inhibit the complexation of photogenerated carriers. Second, the construction of the heterojunction greatly facilitates the transport of carriers and the separation of electrons and holes driven by the built-in electric field. Finally, the abundant oxygen vacancies in the system result in defective energy levels that not only promote the activation of molecular oxygen, but also act as photogenerated electron traps, which further boost the separation of electron-hole pairs. Benefiting from the optimized performance, the photocatalytic reaction rates of S-doped g-C3N4/Bi5O7I are 5.2 and 2.1 times higher than those of g-C3N4 and Bi5O7I, respectively. This work provides a viable idea for the potential development of non-metal doping combined with heterojunction photocatalytic systems.
ABSTRACT
The literature on trace element pollutants (arsenic, selenium, lead) produced during coal burning from 2007 to 2020 was summarized by the bibliometric method, and the characteristics of published articles and research trends were analyzed. Taking 2007 as the starting point for statistics on articles in this research direction, there was a process of rapid growth in the total number of published articles by 2015, and it was increased over time. In the last 5 years of statistics, it is found that the number of articles published in China is the largest, accounting for almost half of the total. Most of the articles are published in the fields of energy, environmental protection, etc. Among them, the research on arsenic, selenium, and lead is mainly related to the use of adsorbents. At the same time, the effects of temperature, catalyst, material, and other conditions on the removal efficiency of arsenic, selenium, and lead in coal were considered. Application of photocatalysis, preparation of new adsorption materials, and mining of the properties of existing materials under different experimental conditions are a good development prospect.
