Solving energy and environmental problems through solar-driven photocatalysis is an attractive and challenging topic. Hence, various types of photocatalysts have been developed successively to address the demands of photocatalysis. Graphene-based materials have elicited considerable attention since the discovery of graphene. As a derivative of graphene, nitrogen-doped graphene (NG) particularly stands out. Nitrogen atoms can break the undifferentiated structure of graphene and open the bandgap while endowing graphene with an uneven electron density distribution. Therefore, NG retains nearly all the advantages of original graphene and is equipped with several novel properties, ensuring infinite possibilities for NG-based photocatalysis. This review introduces the atomic and band structures of NG, summarizes in situ and ex situ synthesis methods, highlights the mechanism and advantages of NG in photocatalysis, and outlines its applications in different photocatalysis directions (primarily hydrogen production, CO2 reduction, pollutant degradation, and as photoactive ingredient). Lastly, the central challenges and possible improvements of NG-based photocatalysis in the future are presented. This study is expected to learn from the past and achieve progress toward the future for NG-based photocatalysis.

The hydrogen economy is a sunrise industry, which is considered the ultimate solution to power the future society. Photocatalytic overall water splitting is projected as a potential technology for H2 production. However, its performance is still far from meeting the criteria for large-scale production. This paper argues that photocatalytic overall water splitting is theoretically and practically hard to achieve. The limiting factors, including unfavorable thermodynamics, slow kinetics, dissolved oxygen, and rapid backward reaction, are discussed. This paper is expected to give readers a better understanding of the photocatalytic overall water splitting and analyze the associated challenges in every subtle aspect.

With the demanding detection of unique toxic gas, semiconductor gas sensors have attracted tremendous attention due to their intriguing features, such as, high sensitivity, online detection, portability, ease of use, and low cost. Triethylamine, a typical gas of volatile organic compounds, is an important raw material for industrial development, but it is also a hazard to human health. This review presents a concise compilation of the advances in triethylamine detection based on chemiresistive sensors. Specifically, the testing system and sensing parameters are described in detail. Besides, the sensing mechanism with characterizing tactics is analyzed. The research status based on various chemiresistive sensors is also surveyed. Finally, the conclusion and challenges, as well as some perspectives toward this area, are presented.

Employing semiconductor photocatalysis to transform solar energy into chemical energy provides a practicable strategy for the alleviation of energy and environmental crisis. Graphitic carbon nitride (g-C3N4) is a popular 2D photocatalyst with numerous advantages, such as visible light response, low cost, and high stability. However, single g-C3N4 photocatalyst displays poor performance due to fast recombination of photogenerated electrons and holes. To improve this limitation, many research works have focused on the construction of g-C3N4-based 2D/2D heterojunction photocatalysts by hybridizing g-C3N4 with other 2D materials. The intimate face-to-face contact in 2D/2D heterojunction offers large contact area and plentiful channels for the migration and separation of photogenerated charge carriers. Furthermore, 2D/2D heterojunction inherits the strengths of 2D structure, including high specific surface area, abundant adsorption sites and active sites. Herein, the preparation, mechanism, and application of g-C3N4-based 2D/2D heterojunction photocatalysts are reviewed. Three common preparation methods are summarized, including solid phase reaction, in situ growth, and electrostatic self-assembly. Various photocatalytic mechanisms are discussed, including traditional type-II, Z-scheme and S-scheme mechanisms. A series of applications in energy and environment fields are illustrated. Finally, future directions for the development of g-C3N4-based 2D/2D heterojunction photocatalysts are proposed.