Extending the Optical Absorption Limit of Graphitic Carbon Nitride Photocatalysts: A Review

Abstract

Due to its chemical/thermal stability, metal-free nature, abundance, low toxicity, cost-effectiveness, high surface area, tunable properties, and ease of synthesis, graphitic carbon nitride (g-C 3 N 4 ) is a promising material for applications in catalysis, sensing, energy storage and optoelectronics. By virtue of its optical band gap, g-C 3 N 4 has been extensively used to drive a range of photocatalytic reactions, such as H 2 generation, CO 2 reduction, N 2 fixation, and organic transformation, to name a few. Despite these prospects, significant improvement in extending its optical absorption is essential because g-C 3 N 4 absorbs light only up to 460 nm (≈10% of the incoming sunlight). Thus, reducing its band gap to harness a wider part of the sunlight is a key approach to advancing the solar energy conversion efficiency of g-C 3 N 4 . In this direction, the effect of (i) improving the degree of polymerization, (ii) molecular and elemental doping, (iii) distorting planar structure, (iv) inducing nitrogen vacancies, and (v) tuning the C/N ratio of g-C 3 N 4 on red-shifting the optical absorption is analyzed in detail. A comprehensive correlation between the synthesis approach/conditions−structure−optical property is established. Rational guidelines on extending the spectral response of g-C 3 N 4 toward the visible/near-infrared region and using low-energy photons to drive photocatalytic reactions efficiently are detailed. The insights presented will help to utilize the full potential of g-C 3 N 4 to enhance the solar fuel generation efficiency and in understanding the mechanism of light absorption.

Promoted Hydrogen Peroxide Production from Pure Water on g-C3N4 with Nitrogen Defects Constructed through Solvent-Precursor Interactions: Exploring A Complex Story in Piezo-Photocatalysis

“…Three deconvoluted peaks at around 437, 456, and 494 nm, corresponding to 2.84, 2.72, and 2.51 eV, as normally observed [32]. The additional peaks in the PL deconvoluted spectra would demonstrate the defective states in the optical bandgap of the materials caused by the cooperation of nitrogen vacancies in different locations [13]. In the CN sample, just one additional peak was deconvoluted with 18.75 % occupancy for the whole However, the solvent-modified samples appear with two deconvoluted peaks with a peak around 520 nm (2.38 eV) occupying roughly 30% of the whole spectra.…”

“…Thus, we proceeded with 13 C solid-state nuclear magnetic resonance (NMR) measurements to certify the hypothesis. As can be seen in Fig.…”

“…X-ray photoelectron spectroscopy (XPS) was employed to analyze the chemical component of materials, while Fourier-transform infrared spectroscopy (FTIR) and 13 C solidstate nuclear magnetic resonance spectroscopy (NMR) were used to the chemical structure of the catalysts. The X-ray diffraction (XRD) technique was applied to study the material crystallinity and defects.…”

“…Thanks to the low-cost synthesis, the high thermal and chemical stability, as well as the possibility to tune the structures, graphitic carbon nitride (g-C3N4) has become the powerful leader in the field of carbon-based photocatalysts since Wang and co-workers first reported its photoactivity [11,12]. However, some demerit points of pristine g-C3N4 restricted its applications, such as the challenge of extending its optical absorption properties [13]. Over time, many proposed methods have been recorded in the literature to overcome the weaknesses of g-C3N4 and accelerate its performance.…”

“…License: CC BY-NC 4.0 generations or water remediation., which can help to rationalize the design and development of the low-cost and efficient materials in the material's perspectives, benefiting both fundamental and applied sides. the as-prepared catalysts measured under darkness (h); 13 C solid-state NMR of the asprepared samples (k) Firstly, in this work, we used Fourier transform infrared (FTIR) spectroscopy to confirm the chemical structures of pristine and modified g-C3N4. As can be observed in Fig.…”