Construction of a 2D/2D g-C₃N₅/NiCr-LDH Heterostructure to Boost the Green Ammonia Production Rate under Visible Light Illumination

Abstract

Photocatalytic N2 fixation has emerged as one of the most useful ways to produce NH3, a useful asset for chemical industries and a carbon-free energy source. Recently, significant progress has been made toward designing efficient photocatalysts to achieve this objective. Here, we introduce a highly active type-II heterojunction fabricated via integrating two-dimensional (2D) nanosheets of exfoliated g-C3N5 with nickel–chromium layered double hydroxide (NiCr-LDH). With an optimized loading of NiCr-LDH on exfoliated g-C3N5, excellent performance is realized for green ammonia synthesis under ambient conditions without any noble metal cocatalyst(s). Indeed, the g-C3N5/NiCr-LDH heterostructure with 2 wt % of NiCr-LDH (CN-NCL-2) exhibits an ammonia yield of about 2.523 mmol/g/h, which is about 7.51 and 2.86 times higher than that of solo catalysts, i.e., NiCr-LDH (NC-L) and exfoliated g-C3N5 (CN-5), respectively, where methanol is used as a sacrificial agent. The enhancement of NH3 evolution by the g-C3N5/NiCr-LDH heterostructure can be attributed to the efficient charge transfer, a key factor to the photocatalytic N2 fixation rate enhancement. Additionally, N2 vacancies present in the system help adsorb N2 on the surface, which improves the ammonia production rate further. The best-performing heterostructure also shows long-term stability with the NH3 production rate remaining nearly constant over 20 h, demonstrating the excellent robustness of the photocatalyst.

Nitrogen‐rich graphitic carbon nitride (g‐C3N5): Emerging low‐bandgap materials for photocatalysis

“…Instantly, Che and coauthors reported how to regulate the direction of charge transfer in modified g‐C 3 N 5 to generate H 2 O 2 under visible light illumination. [ 76 ] In this study, they used the doping technique to modulate the electronic structures of g‐C 3 N 5 to reduce oxygen to generate H 2 O 2 efficiently. Specifically, they compared three systems, including pure g‐C 3 N 5 , K, Cl codoped g‐C 3 N 5 , and K, I codoped g‐C 3 N 5 , and disclosed that K, I codoped samples would give significant enhancement in the generation of H 2 O 2 because the modified samples accelerated the kinetic formation rate with enhancing O 2 adsorption properties and extended light absorption capacity with the robust catalysts' stability.…”

TiO2 Quantum Dots/Fe3S4 Heterojunction Nanocomposites for Efficient Ammonia Production through Nitrogen Fixation upon Simulated Sunlight

“…Moreover, in order to prove that the nitrogen gas for the photocatalytic reduction reaction is supplied from the air pump, instead of using the air pump, argon gas was bubbled into the reaction system. Considering that the amount of ammonia production decreased to 664 μmol L –1 g –1 , it shows that nitrogen gas is a key reactant, which is supplied by the air pump. , Using the Watt–Chrisp method, the concentration of hydrazine formed in the photocatalytic nitrogen fixation as an intermediary species was explored, and the results are presented in Figure e . According to this figure, the amount of hydrazine production was almost constant after three hours of exposure to simulated sunlight over the TiO 2 QDs/Fe 3 S 4 20% nanocomposite.…”

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

“…Bharati Debnath [ 70 ] designed a g-C 3 N 5 /NiCr-LDH heterostructure, a hybrid of g-C 3 N 5 and NiCr-layered double hydroxide. DFT calculations showed its ability to adsorb and activate N 2 molecules.…”

“… ( a – d ) Initial structure (red circles: the binding position); ( e – h ) corresponding optimized structures; ( i – l ) corresponding N−N bond distances; ( m ) Photocatalytic ammonia production rates of g-C 3 N 5 /NiCr-LDH; ( n ) Schematic illustration of a mechanism for NH 3 production using g-C 3 N 5 /NiCr-LDH; ( o – p ) In-situ DRIFTS spectra of B-C 3 N 5 ; ( q ) NH 3 yields for g-C 3 N 5 and B-C 3 N 5 x (x = 1, 2, 3). ( a – n ) Adapted with permission from [ 70 ]. Copyright Elsevier B.V., 2022.…”