Freestanding Graphitic Carbon Nitride Photonic Crystals for Enhanced Photocatalysis

Abstract

1wileyonlinelibrary.com on crystalline and molecular engineering could turn the band gap of g-C 3 N 4 by element doping, [4] using different precursors, [5][6][7][8][9] introducing crystal defects or amorphous structure, [3,10,11] forming carbon vacancies, [12] fabricating heterojunction composites, [13][14][15] and so on. Structural regulation mainly focused on increasing specific surface area, [16][17][18][19][20][21] typically making mesoporous by templates with high specific surface area. [16,17,20,21] However, most of studies reported focused on g-C 3 N 4 in the powder form due to the contradiction between the highly open framework and the insufficient mechanical strength. Some recent progresses have been made to achieve 3D macroform g-C 3 N 4 based on robust substrate, [19] but major challenges remain to develop a substrate-free g-C 3 N 4 film with high photocatalytic activity. Photonic crystals (PCs) are materials with spatially periodic variation of the dielectric permittivity on the order of the wavelength of light. The propagation of light within a certain frequency range is forbidden in a certain crystal direction within a certain spectrum regime, namely photonic stopband. [22,23] Special properties of PCs, such as inhibition of spontaneous emission, [24][25][26] slow light, and amplified photon absorption/emission, [27][28][29][30] provide numerous possibilities for "photon management" applications. Thus introducing PC structure is a promising strategy for promoting photocatalytic activity of photocatalyst and the performance in optoelectronic devices. [27][28][29][30][31][32][33] Consequently, if g-C 3 N 4 is fabricated in a PC form, the spontaneous emission by the recombination of photogenerated carriers could be inhibited and the photocatalytic activity could benefit from the bicontinous network with increased visible light absorption via slow photon effects.Inspired by considerations above, herein we demonstrate a general solution approach to tackle the challenge via a freestanding colloidal crystal templating method (see Scheme 1). Freestanding, highly ordered, crack-free silica PCs are generated by evaporative-vertical deposition. Subsequently, the calcination of the precursor dicyandiamide (DCDA) followed by removal of silica PCs generates highly uniform macroscopic g-C 3 N 4 PC films. The resultant freestanding g-C 3 N 4 PCs possesses a 3D interconnected network with tunable photonic stop band, exhibiting significantly improved photocatalytic activity in photodegrading and water splitting under visible light. Freestanding Graphitic Carbon Nitride Photonic Crystals for Enhanced PhotocatalysisLu Sun, Meijia Yang, Jianfeng Huang, Dingshan Yu, Wei Hong,* and Xudong Chen* Graphitic carbon nitride (g-C 3 N 4 ) has attracted tremendous attention in photocatalysis due to its extraordinary features, such as good thermal and chemical stability, metal-free composition, and easy preparation. However, the photocatalytic performance of g-C 3 N 4 is still restricted by the limited surface area, inefficient v...

Heteroatom‐Doped Carbonaceous Photocatalysts for Solar Fuel Production and Environmental Remediation

“…Fabrication of g‐C 3 N 4 3D macroscopic structures have the potential to address the above issues. g‐C 3 N 4 macroscopic structures have been successfully prepared by supramolecular preorganization, hard template, and a one‐step cryodesiccation routes …”

“…PCNM exhibits ≈2 times higher S BET , remarkably promoted light harvesting capability, owing to the multiple reflections, and a much lower E g by 0.63 eV, no PL emission peak, notably lowered resistance of electron transfer, and significantly promoted photocurrent in contrast to bulk g‐C 3 N 4 . Another example for the synthesis of 3D g‐C 3 N 4 macroscopic structure was reported by Sun and coworks by employing a crack‐free, highly‐ordered colloid crystal templating method . By using monodispersed SiO 2 nanospheres (size 200 nm) as the template, highly ordered 3D g‐C3N4 photonic crystals (PCs) photocatalysts (200‐C 3 N 4 ) could be obtained (Figure ).…”

“…To overcome the disadvantage of bulk g‐C 3 N 4 , a range of N‐doped nanocarbons have been developed (g‐C 3 N 4 nano/micro structures, g‐C 3 N 4 ‐based hybrids, highly crystal and amorphous carbon nitride). Moreover, to address the complicated recovery of powder photocatalysts from photocatalytic reactions, g‐C 3 N 4 ‐based 3D macroscopic structures have also been fabricated . The applications of the aforementioned novel and efficient N‐doped carbonaceous photocatalysts for solar fuel conversion and environmental purification are summarized and discussed as follows.…”

“…It is, therefore, highly desirable to develop g‐C 3 N 4 ‐based 3D macroscopic structures that address these issues. Recently, some work focused on the construction of g‐C 3 N 4 ‐based 3D macroscopic photocatalysts for hydrogen generation and degradation of pullutants . Liang et al.…”

“…compared the photocatalysis of as‐fabricated 3D macroscopic photonic crystals (200‐C 3 N 4 ) with bulk g‐C 3 N 4 and disordered mesoporous g‐C 3 N 4 (Dis‐C 3 N 4 ) for hydrogen generation from water splitting and MO degradation. Results show that 3D 200‐C 3 N 4 macroscopic structure exhibits much superior catalytic performance (HER: 1979 μmol g −1 h −1 ; MO degradation rate: 100 % after 45 min) to bulk g‐C 3 N 4 (HER: 224.4 μmol g −1 h −1 ; MO degradation rate: 23 % after 4 h) and Dis‐C 3 N 4 (HER: 1260 μmol g −1 h −1 ; MO degradation rate: 98 % after 2 h), ascribed to the promoted light absorption owing to multiple scattering in hierarchical pores, slow photon effects and lower E g , the efficiently inhibited recombination of charge carriers due to the stop band suppression, and the promoted separation of electron‐hole pairs . For another example, Wan et al.…”