Ordered Mesoporous C₃N₅ with a Combined Triazole and Triazine Framework and Its Graphene Hybrids for the Oxygen Reduction Reaction (ORR)

Abstract

Mesoporous carbon nitrides (MCN) with C 3 N 4 stoichiometry could find applications in fields ranging from catalysis,sensing, and adsorption-separation to biotechnology. The extension of the synthesis of MCN with different nitrogen contents and chemical structures promises access to aw ider range of applications.H erein we prepare mesoporous C 3 N 5 with acombined triazole and triazine framework via asimple self-assembly of 5-amino-1H-tetrazole (5-ATTZ). We are able to hybridizet hese nanostructures with graphene by using graphene-mesoporous-silica hybrids as at emplate to tune the electronic properties.D FT calculations and spectroscopic analyses clearly demonstrate that the C 3 N 5 consists of 1triazole and 2triazine moieties.T he triazole-based mesoporous C 3 N 5 and its graphene hybrids are found to be highly active for oxygen reduction reaction (ORR) with ah igher diffusionlimiting current density and ad ecreased overpotential than those of bulk g-C 3 N 4 .

Thermodynamically Stable Mesoporous C3N7 and C3N6 with Ordered Structure and Their Excellent Performance for Oxygen Reduction Reaction

“…The peak at 810 cm −1 observed for all materials corresponds to condensed CN heterocycles . The mesoporous C 3 N 7 , C 3 N 6 and C 3 N 5 show the vibration bands at 775 and 740 cm −1 which are attributed to NN heterocycles, indicating that core structures of the mesoporous C 3 N 7 and C 3 N 6 are composed of not only triazine moiety but also tetrazine and/or triazole moieties . These chemical bonding characteristics of the mesoporous C 3 N 7 and C 3 N 6 are in quite contrast with those of the g‐C 3 N 4 .…”

“…As displayed in Figure b, C K‐edge NEXAFS spectra of the mesoporous C 3 N 7 , C 3 N 6 , and C 3 N 5 present two peaks at 285.2 and about 288.3 eV attributed to π* (out of plane CC) and π* (NCN) excitations, respectively . Considering that g‐C 3 N 4 presents π* (NCN) excitation at 288.0 eV, the mesoporous C 3 N 7, C 3 N 6 and C 3 N 5 show a blue shift of π* (NCN) excitation owing to an increase of NC  N bond strength as compared to g‐C 3 N 4 due to existence of neighboring NN bond in their structures. In N K‐edge spectra (Figure c), the mesoporous C 3 N 7 , C 3 N 6 and C 3 N 5 exhibit two intense peaks of A and B at 399.1 and about 400.2 eV that correspond to π* (NCN) and π* (heterocyclic NN) excitations, respectively .…”

“…Because of its semiconducting property and diverse functionalities, the g‐C 3 N 4 attracts intense research interest for water splitting, redox catalysis, sensing and gas adsorption . Besides the g‐C 3 N 4 , nonstoichiometric and N‐rich carbon nitrides such as C 3 N 5 and C 3 N 6 have been explored by many researchers . Our group was successful in preparing mesoporous s‐heptazine‐based C 3 N 5 with terminal groups of triazole using a precursor of 3‐amino‐1,2,4‐triazole which showed excellent photocatalytic and sensing properties .…”

“…Although most of the N‐rich carbon nitrides consist of s‐heptazine moiety, Kim et al and Talapaneni et al synthesized non‐s‐heptazine‐based N‐rich carbon nitrides from 5‐amino‐1H‐tetrazole (5‐ATTZ) and aminoguanidine hydrochloride respectively, which are triazole‐based C 3 N 5 and diaminotetrazine‐based C 3 N 6 , respectively . By varying the nature of the carbon nitride precursors, new family of carbon nitride with a high nitrogen content and unique chemical structure could be prepared.…”

“…The synthetic temperatures of 250 and 300 °C were fixed based on thermogravimetric analysis (TGA) results for 5‐ATTZ (see Figure S1, Supporting Information) . Elemental (CHN) analysis (see Table S1, Supporting Information) shows that chemical compositions of the samples calcined at 250 and 300 °C are C 3 N 6.7 (≈C 3 N 7 ) and C 3 N 5.6 (≈C 3 N 6 ), respectively, which suggest a successful tuning of the chemical composition of carbon nitride with the N/C ratio from 1.87 to 2.23.…”