Ti₃C₂T_x intercalation, modification and application in enzymatic CO₂ conversion

Ti₃C₂T_xas a typical MXene material has a multilayer structure similar to accordion, whose interlayer spacing and specific surface area can be regulated by intercalation and modification. In this work, the effects of several kinds of cation-containing intercalators including NH₄OH, KOH and NH₄OH/KCl on the structure of Ti₃C₂T_x and its application performance in enzymatic CO₂ conversion were investigated for the first time. The results show that Ti₃C₂T_x intercalated with NH₄OH/KCl had larger layer spacing (25.25 Å) and specific surface area (20.85 m²/g), and better enhancing effect. The initial reaction rate was 0.379 mM/h, which was separately 1.04, 1.42, 1.76 and 5.29 times that of Ti₃C₂T_x/KOH, Ti₃C₂T_x/NH₄OH, Ti₃C₂T_x and the blank system. Following that, Ti₃C₂T_x/NH₄OH/KCl was modified by polyethyleneimine (PEI) and dopamine (DA) and the concentration of modifier was optimized. PEI modified Ti₃C₂T_x/NH₄OH/KCl (PEI-Ti₃C₂T_x) was superior to PEI/DA modified that in the N content, CO₂ adsorption capacity and application performance. With the addition of 20 mg PEI-Ti₃C₂T_x, the initial reaction rate was 0.658 mM/h, which was 1.74 and 9.2 times that of before modification and the blank system, respectively. PEI-Ti₃C₂T_x also exhibited a good reusability and the initial reaction rate was 89.4% of the initial value after 10 cycles.