CxNy: New Carbon Nitride Organic Photocatalysts

Abstract

The search for metal-free and visible light-responsive materials for photocatalytic applications has attracted the interest of not only academics but also the industry in the last decades. Since graphitic carbon nitride (g-C3N4) was first reported as a metal-free photocatalyst, this has been widely investigated in different light-driven reactions. However, the high recombination rate, low electrical conductivity, and lack of photoresponse in most of the visible range have elicited the search for alternatives. In this regard, a broad family of carbon nitride (CxNy) materials was anticipated several decades ago. However, the attention of the researchers in these materials has just been awakened in the last years due to the recent success in the syntheses of some of these materials (i.e., C3N3, C2N, C3N, and C3N5, among others), together with theoretical simulations pointing at the excellent physico-chemical properties (i.e., crystalline structure and chemical morphology, electronic configuration and semiconducting nature, or high refractive index and hardness, among others) and optoelectronic applications of these materials. The performance of CxNy, beyond C3N4, has been barely evaluated in real applications, including energy conversion, storage, and adsorption technologies, and further work must be carried out, especially experimentally, in order to confirm the high expectations raised by simulations and theoretical calculations. Herein, we have summarized the scarce literature related to recent results reporting the synthetic routes, structures, and performance of these materials as photocatalysts. Moreover, the challenges and perspectives at the forefront of this field using CxNy materials are disclosed. We aim to stimulate the research of this new generation of CxNy-based photocatalysts, beyond C3N4, with improved photocatalytic efficiencies by harnessing the striking structural, electronic, and optical properties of this new family of materials.

Accurate design of porous g-C3N4+x with greatly extended visible-light response for enhanced photocatalytic performance and mechanism insight for environmental remediation

“…However, few research has been focused on chemical structure modification, which will result in novel physicochemical properties for photocatalytic applications. It should be noted the change of the C/N ratio has been confirmed as an effective route to modify the electronic structure and photocatalytic performance of C 3 N 4 [18].…”

Engineered g-C3N5-Based Nanomaterials for Photocatalytic Energy Conversion and Environmental Remediation

“…Semiconductor-based photocatalysis is regarded as one of the most efficient technologies to address serious energy and environmental issues [ 5 , 6 , 7 ]. The mass production of highly efficient, dependable, and reasonably priced photocatalysts with strong charge carrier segregation, plenty of active sites, a broad optical absorption range, and high redox potentials is crucial for the commercialization of photocatalytic technology [ 8 , 9 , 10 ]. As a result, much effort has been devoted to designing more robust and efficient photocatalysts.…”

Optimizing dicyandiamide pretreatment conditions for enhanced structure and electronic properties of polymeric graphitic carbon nitride

“…Therefore, the development of a cheaper and more environmentally sustainable approach is highly desired. 22 The emergence of graphitic carbon nitride has sparked extensive debates concerning its pseudographite phase formation during precursor polymerization, raising inquiries about its degree of condensation, whether fully or partially condensed. [23][24][25] To date, most of the prepared CN materials are the melon type (C 6 N 9 H 3 ) with a C/N ratio of 0.67.…”

“…Therefore, the development of a cheaper and more environmentally sustainable approach is highly desired. 22…”