Self-supported hierarchical crystalline carbon nitride arrays with triazine-heptazine heterojunctions for highly efficient photoredox catalysis

Elucidating the Effect of Crystallinity on the Photoactivity in Poly(heptazine imides)

“…All of the samples display XRD signals at 2θ of about 27° and 12°, which correspond to the (002) and (100) planes of CN, respectively (Figure a); a small shift occurs as the relative salt amount is increased, which can be ascribed to the intercalation of salt ions within the CN structure. , Additionally, a diffraction signal is present at approximately 8°, whose intensity is maximal for DCDBA5 and decreases at higher salt/reactant ratios; this peak can be assigned to the (100) plane of PHI structures and corresponds to a spacing distance d (100) of approximately 1.1 nm. , In the case of DCDBA20, however, the XRD pattern shows the formation of a crystalline PTI structure with 2θ values (10.6°, 18.4°, 22.9°, 24.7°, 26.6°, 28.0°, and 31.0°) that are slightly different from those commonly reported for PTI/Li + Cl – ; − we ascribe this variation to the use of different salt ions in this work.…”

“…As observed, the reported PHI-based materials that display high visible-light photocatalytic activities have significantly stronger (100) plane intensity in their XRD patterns compared to other samples in this work and other reported works. 27,48,50 The intensity ratio of the diffraction peaks at 8°a nd 27°may be used to determine the proportion of (100) planes with repeating order within the PHI moiety, because the different CN samples (including bulk CN, PTI, or PHI) display a similar peak at approximately 27°, which is related to the interlayer stacking, that is, the (002) plane. 1,3,20,47,48 The HER activity metric and the XRD intensity ratio I (100) /I (002) measured in different CNs (Figure 5a) show a direct correlation with an excellent linear fit (R 2 = 0.918; Figure S23 of the Supporting Information).…”

Effect of molten-salt modulation on the composition and structure of g-C3N4-based photocatalysts

“…The array structure is more suitable for photoredox catalysis due to the fast diffusion of the electrolyte, high efficiency of gas production, fast electron transmission, and low interfacial resistance. Furthermore, self-supported omasum-like crystalline carbon nitride arrays were constructed by Huang et al 76 They prepared rod-like melamine-based supramolecular precursors by a green, molten salt-assisted heat-treatment method. They showed triazine-heptazine heterostructures to have efficient charge separation and transfer, excellent performance of photocatalytic hydrogen evolution, as well as excellent oxidation activity and stability of aromatic hydrocarbons.…”

Recent advances in high-crystalline conjugated organic polymeric materials for photocatalytic CO2conversion

“…146 In addition, the heterojunctions with different crystal phases of the same material can remarkably eliminate the interfacial defects. 144,147,148 The built-in electric field formed by this close contact heterogeneous interface (Fig. 13b) and improved crystallinity make the catalyst much better.…”