2D MXene-derived Nb₂O₅/C/Nb₂C/g-C₃N₄ heterojunctions for efficient nitrogen photofixation

Abstract

Due to the rather high 940.95 kJ mol-1 thermodynamically cleavage energy of N-N triple bond, developing a robust catalytic process for the N2 reduction under mild conditions is a continuing...

Advances and Promises of 2D MXenes as Cocatalysts for Artificial Photosynthesis

“…However, only a few metal oxide semiconductors can be synthesized through the in situ oxidation, such as TiO 2 /Ti 3 C 2 T x and Nb 2 O 5 /Nb 2 CT x composites, due to the limitation of the kinds of transition metal elements in MXenes. [117][118][119] Considering the unique structure of MXenes, they could be better supporting materials than graphene for constructing heterojunction photocatalysts with 0D, 1D, and 2D semiconductors, [120][121][122] as shown in Figure 10d. [123] Through the aforementioned three synthetic routes, various and c) in situ oxidation of Ti 3 C 2 MXene precursor for the preparation of TiO 2 /Ti 3 C 2 heterojunction.…”

“…Furthermore, Bian and co-workers developed a Nb 2 O 5 /C/ Nb 2 C/g-C 3 N 4 catalyst used for photocatalytic N 2 reduction in water under mild conditions through in situ partial oxidation of Nb 2 CT x MXene and subsequent combination with g-C 3 N 4 . [118] In comparison with the Nb 2 O 5 /g-C 3 N 4 composite, the nitrogen reduction rate on Nb 2 O 5 /C/Nb 2 C/g-C 3 N 4 sample increased by 9.1 times to 0.365 mmol g À1 h À1 (Figure 17c), due to the formation of Schottky junctions and the close interface between Nb 2 O 5 and Nb 2 C, which is beneficial to the separation of photoinduced electron-hole pairs and the transfer of charge carriers (Figure 17d). The research on MXene/semiconductor composites for photocatalytic nitrogen fixation is just beginning and there are lots of problems under debate, such as the N 2 adsorption model on the surface of MXenes and the N 2 photofixation process.…”

Photocatalytic one‐pot multidirectional N‐alkylation over Pt/D‐TiO2/Ti3C2: Ti3C2‐based short‐range directional charge transmission

“…In order to acquire a deeper understanding of the role of light in the reaction, we investigated the effect of wavelength on one-pot hydrogenation and N-alkylation. The catalytic activity was generally maintained with the irradiation of UV, white or green LEDs (Table 1, entries [17][18][19]. However, the chemoselectivity of E1 was significantly decreased to 46.3% with UV.…”

“…Aromatic nitro compounds having different substituents could be reacted with benzyl alcohol to prepare N-alkylamines or N-benzylideneanilines on the irradiated 3%Pt/D-TiO 2 /Ti 3 C with good to excellent activity and chemoselectivity. In comparison with nitrobenzene, aromatic nitro compounds with different substituents generally had a good catalytic activity; the electron-donating group on the aromatic nitro compound was more favorable for catalytic activity than the electron-withdrawing group (Table 2, entries 3-12 vs. [13][14][15][16][17][18]. When the aromatic nitro compounds had methyl substituent (Table 2, entries 3-8), the reactivity order, onitrotoluene < m-nitrotoluene < p-nitrotoluene, should be owing to the steric hindrance effect.…”

“…[11][12][13] The emerging 2D transition metal carbide/carbonitride family (MXenes), with general formula M n + 1 X n T x (n = 1, 2, 3; T x = OH, O, F group), has been extensively studied during the past few years due to its excellent structure and chemical properties. [14][15][16][17][18][19] MXene's excellent electron conductivity makes it easier to transfer charge from the semiconductor to MXene, thereby improving the separation efficiency of electron and hole, thus achieving directional charge transmission. [20,21] With the above special characteristics, MXene is considered as one of the most promising catalytic material.…”