Fabricated layered g-C3N4 nanosheets for high efficiency photocatalytic degradation of atrazine：Insight into terminal-NHx in-situ activation of H2O2.

It is well known that graphite-like carbon nitride (g-C 3 N 4) is a good photocatalyst for in-situ the production of H 2 O 2. However, how to activate H 2 O 2 generating the strong oxidizing ·OH is the key factor to affect the degradation of pollutants. In this paper, the layered g-C 3 N 4 nanosheets were prepared by using urea and H 2 O with different mass ratios and calcined in Muffle furnace by one-step synthesis method. The morphology, composition and structure of photocatalysts were analyzed, indicating that the as-prepared L-g-C 3 N 4 -7 had abundant edge regions in comparison with L-g-C 3 N 4 made by solid urea. The photocatalytic performance of g-C 3 N 4 nanosheets was investigated with atrazine (ATZ) as the target pollutant in water. The results revealed that the prepared L-g-C 3 N 4 -7 exhibited the best photocatalytic activity in visible light (λ ≥ 420 nm). The degradation of 1.0 mg/L ATZ reached over 96% after 3 hours and the photocatalytic degradation rate constant (k) was 6.8 times than that of L-g-C 3 N 4 photocatalyst. In addition, under the same conditions, the H 2 O 2 production of L-g-C 3 N 4 -7 was 4.5 times than that of L-g-C 3 N 4 photocatalyst. Based on the capture experiments of free radicals, it was found that the contribution rate of ·OH in L-g-C 3 N 4 -7 photocatalytic increased to 17 % compared to 4 % of L-g-C 3 N 4 photocatalyst during the degradation of ATZ. The ·OH quantitative experiment indicated that the L-g-C 3 N 4 -7 photocatalyst could obviously activate H 2 O 2 to generate ·OH and the amount of ·OH was 2.5 times than that of the L-g-C 3 N 4 photocatalyst. More importantly, a large amount of terminal-NH x (14.6 %) in L-g-C 3 N 4 -7 was measured by the XPS, FT-IR and zeta potential. The additive H 2 O 2 adsorption experiment in the dark was used to confirm terminal-NH x sites of L-g-C 3 N 4 -7 photocatalyst, which was beneficial to adsorb and activate H 2 O 2. The results illustrated that the L-g-C 3 N 4 -7 photocatalyst with rich edge regions and terminal-NH x had the characteristics of in-situ the activation of H 2 O 2 to generate ·OH. The findings suggest that designing and developing efficient g-C 3 N 4 photocatalysts pave a new avenue for activating in situ self-synthesizing H 2 O 2 and the removal of atrazine in water. [Display omitted] • The L-g-C 3 N 4 -7 photocatalyst with rich edge regions had a high efficiency in-situ activation of H 2 O 2 to produce ·OH. • The main reason for the degradation of ATZ in L-g-C 3 N 4 -7 photocatalyst was the increasing contribution of ·OH. • The terminal-NH x of L-g-C 3 N 4 -7 was the main adsorption and activation site of H 2 O 2. [ABSTRACT FROM AUTHOR]