MIL-100(Fe)/Ti₃C₂ MXene as a Schottky Catalyst with Enhanced Photocatalytic Oxidation for Nitrogen Fixation Activities

Abstract

A new microporous MIL-100­(Fe)/Ti3C2 MXene composite was constructed as a non-noble metal-based Schottky junction photocatalyst with improved nitrogen fixation ability. Ti3C2 MXene nanosheets exhibited excellent metal conductivity and were employed as two-dimensional support to optimize the composite’s energy band structure. MIL-100­(Fe) with a large specific surface area was used as an adsorbent and a photocatalytic oxidation center. The MIL-100­(Fe)/Ti3C2 MXene composite not only exhibited higher thermal stability but also showed significantly increased nitrogen fixation activity under visible light. The NO conversion rate of the composite catalyst was about four and three times higher than that of the pure Ti3C2 MXene and the pure MIL-100­(Fe) samples, respectively. Although adsorption plays an important role in the nitrogen fixation process, the synergistic effects of the Schottky junctions are the main cause of the enhanced photocatalytic activity. The built-in electric field can be generated to form charge-transfer channels, which help to achieve a desirable photocatalytic activity.

Fundamentals and Recent Progress of Photocatalytic Nitrogen‐Fixation Reaction over Semiconductors

“…Until 2013, Yuan et al demonstrated the oxidation of N 2 in air to HNO 3 on TiO 2 under sunlight, and NO was found to be an intermediate in this process, in which two possible mechanisms of photocatalytic N 2 oxidation to NO were proposed based on the theoretical calculation. [ 34 ] According to this statement and combination with the other studies in this field, [ 33,68 ] the following two mechanisms of photocatalytic NOR are drawn in Figure .…”

“…In principle, NOR will occurs when the N 2 molecule eventually loses the electrons on catalyst surface, and the products are generally considered to be NO and NO 3 − (the product of further oxidation of NO). [ 33–35,68 ] At this occasion, the photoexcited electrons in the CB of semiconductor are usually transferred to O 2 molecule. The involved equations are as follows…”

“…Obviously, the differences between the two NOR mechanisms can be summarized as follows: [ 33,34,68 ] 1) The O atom of NO comes from the reactant O 2 in the CB mechanism, whereas that of NO originates for the reactant H 2 O in the VB mechanism. Theoretically, if H 2 O and O 2 with 18 O labeled were used as reactants, the reaction mechanism would be confirmed by measuring the mass spectra of the intermediate (NO) or the final product (NO 3 − ).…”

Inside‐and‐Out Semiconductor Engineering for CO2 Photoreduction: From Recent Advances to New Trends

“…Interfaces between two adjacent components play a vital role in charge carriers transfer, because the structure of interface impacts electron–hole pair migration from light‐harvesting component to surface active sites. [ 342–345 ] As a typical metal–semiconductor junction and one of the most desirable semiconductor–semiconductor junctions, Schottky junction and Z‐scheme junction will be discussed here.…”

Preparation of macroporous hybrid monoliths via iron‐based MOFs‐stabilized CO2‐in‐water HIPEs and use for β‐amylase immobilization

“…The absorption peaks at 1629 and 1375 cm −1 are attributed to the C O and C O stretching vibrations, respectively. The bands at 760 and 713 cm −1 are assigned to bending vibrations of C H on the benzene ring, and the band at 481 cm −1belongs to Fe O stretching vibrations 40. In curve b, the wide peak centered at 3425 cm −1 belongs to the stretching vibrations of the O H. The two distinct peaks at 1570 and 1387 cm −1 correspond to asymmetric and symmetric vibrations of carboxyl groups,41 respectively.…”