Photoreduction of N₂ is among the most interesting and challenging methods for N₂ fixation under mild conditions. In this study, we determined that nitrogen vacancies (NVs) could endow graphitic carbon nitride (g-C₃N₄) with the photocatalytic N₂ fixation ability. Photocatalytic N₂ fixation induced by NVs is free from the interference of other gases. The reason is that NVs could selectively adsorb and activate N₂ because NVs have the same shape and size as the nitrogen atom in N₂. In addition to this, NVs could also improve many other properties of g-C₃N₄ to support photocatalytic N₂ fixation. These new findings could elucidate the design of efficient photocatalysts for photocatalytic N₂ fixation.

Selective photocatalytic N₂ fixation dependent on g-C₃N₄ induced by nitrogen vacancies

The poor utilization of visible light and the speedy recombination of photoexcited carriers limit the further development of carbon nitride polymer (CN) photocatalysts. It is a valid means for enhancing the photocatalytic ability to ameliorate the electronic and physicochemical properties via modifying the structure of CN. The sulfur- and chlorine-codoped graphite CN (S/Cl-CN) was successfully fabricated with low-cost ammonium chloride and thiourea as precursors. The introduction of Cl atoms will establish interlayer channels to promote interlayer charge migration and up-shifted conduction-band level. S atom is appropriate to be incorporated into the CN framework to replace N atom, which is beneficial to adjust the band gap. Then, inorganic-organic CdSe-diethylenetriamine (D) grown in situ are employed to fabricate a S/Cl-CN/CdSe-D heterojunction. S/Cl-CN/CdSe-D heterojunction exhibits greater hydrogen evolution activity compared to CN, S-CN, Cl-CN, S/Cl-CN, CdSe-D and CN/CdSe-D. Finally, Step-scheme (S-scheme) photocatalytic mechanism based on S/Cl-CN/CdSe-D heterostructure was proposed.

Two-dimensional sulfur- and chlorine-codoped g-C3N4/CdSe-amine heterostructures nanocomposite with effective interfacial charge transfer and mechanism insight

A review on heterogeneous photocatalysis for environmental remediation: From semiconductors to modification strategies

Over the past few decades, graphitic carbon nitride (g-C3 N4 ) has arisen much attention as a promising candidate for photocatalytic hydrogen evolution reaction (HER) owing to its low cost and visible light response ability. However, the unsatisfied HER performance originated from the strong charge recombination of g-C3 N4 severely inhibits the further large-scale application of g-C3 N4 . In this case, the utilization of cocatalysts is a novel frontline in the g-C3 N4 -based photocatalytic systems due to the positive effects of cocatalysts on supressing charge carrier recombination, reducing the HER overpotential, and improving photocatalytic activity. This review summarizes some recent advances about the high-performance cocatalysts based on g-C3 N4 toward HER. Specifically, the functions, design principle, classification, modification strategies of cocatalysts, as well as their intrinsic mechanism for the enhanced photocatalytic HER activity are discussed here. Finally, the pivotal challenges and future developments of cocatalysts in the field of HER are further proposed.

Emerging Cocatalysts on g-C3N4 for Photocatalytic Hydrogen Evolution

The effective separation of photogenerated carriers plays a vital role in photocatalytic reactions. In addition to the intrinsic driving force of photocatalysis, an external field generating an enh...

Recent Advances in Noncontact External-Field-Assisted Photocatalysis: From Fundamentals to Applications

Sulfur-doped two-dimensional (2D) graphitic carbon nitride nanosheets (2D-SCN) with efficient photocatalytic activity were synthesized via (1) polycondensation of thiourea to form bulk sulfur-doped...

Synthesis of Sulfur-Doped 2D Graphitic Carbon Nitride Nanosheets for Efficient Photocatalytic Degradation of Phenol and Hydrogen Evolution

Modification of a photocatalyst with single-atom noble metals can improve its activity while a remaining challenge is the stabilization of single atoms. As a proof of concept, g-C3N4 with desired amount of carbon defects was fabricated to manipulate the distribution of single-atom Pd by taking advantage of its affinity with carbon vacancy-resulted nitrogen atoms. The single-atom Pd was produced by photo-reduction, preferentially located on the carbon vacancy sites as supported by HAADF-STEM and XAFS analyses. As obtained photocatalyst showed high and stable photocatalytic activity in NO conversion; its activity is about 4.4 times higher than that of the pristine g-C3N4. The improved photoactivity was attributed to the preferential separation and transportation of the photo-generated charge carriers due to the introduction of single-atom Pd as evidenced by UV–vis, static and time-resolved photoluminescence spectroscopic analyses. The present work underlines the impetus of surface defect chemistry in the fabrication of single-atom catalysts.

Ying Huang

Papers

Synthesis of Sulfur-Doped 2D Graphitic Carbon Nitride Nanosheets for Efficient Photocatalytic Degradation of Phenol and Hydrogen Evolution

Confining single-atom Pd on g-C3N4 with carbon vacancies towards enhanced photocatalytic NO conversion

Oxygen-doping of ZnIn2S4 nanosheets towards boosted photocatalytic CO2 reduction