Construction of a 2D/2D g-C 3 N 5 /NiCr-LDH Heterostructure to Boost the Green Ammonia Production Rate under Visible Light Illumination.

Photocatalytic N 2 fixation has emerged as one of the most useful ways to produce NH 3 , 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-C 3 N 5 with nickel-chromium layered double hydroxide (NiCr-LDH). With an optimized loading of NiCr-LDH on exfoliated g-C 3 N 5 , excellent performance is realized for green ammonia synthesis under ambient conditions without any noble metal cocatalyst(s). Indeed, the g-C 3 N 5 /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-C 3 N 5 (CN-5), respectively, where methanol is used as a sacrificial agent. The enhancement of NH 3 evolution by the g-C 3 N 5 /NiCr-LDH heterostructure can be attributed to the efficient charge transfer, a key factor to the photocatalytic N 2 fixation rate enhancement. Additionally, N 2 vacancies present in the system help adsorb N 2 on the surface, which improves the ammonia production rate further. The best-performing heterostructure also shows long-term stability with the NH 3 production rate remaining nearly constant over 20 h, demonstrating the excellent robustness of the photocatalyst.