Introduction
MAX phases are stacked layers of ternary carbides composed of a transition metal, an A-group element, and carbon/or nitrogen. MXenes are a class of materials produced through selective etching of the A-group element within their corresponding MAX phases parents. The traditional etching method for the synthesis of MXenes involves the use of hazardous substances and highly corrosive chemicals, namely the fluorine-based salts. As an alternative, MXenes can be also produced by an electrochemical etching method. One of the main advantages of this method is the use of salts with moderate toxicity and the ability to control the entire etching process by adjusting the applied potential. In this work, an electrochemical method was explored for the production of Ti3C2Tx MXene.
Methods
First, Ti3C2Tx was synthesized by the electrochemical etching of Ti3AlC2 in an electrolyte containing choline chloride and tetrafluoroboric acid at different applied voltages. Then, a heterojunction was fabricated by the drop casting of the synthesized Ti3C2Tx, previously modified with Ni, on titania nanotubes (Ni-MXene-TiO2) and underwent rapid thermal treatment in a hydrogen atmosphere (h-Ni-MXene-TiO2).
Results
The recorded Raman spectra indicate that the MXene structure can be obtained after 8 h of bipolar etching. However, the yield of the produced MXene decreases significantly with increases in the applied voltage. The SEM images showed that the accordion structure of Ti3C2Tx appears when a voltage of 1 V is applied between the electrodes for 16 h.
This material has been selected for further characterization by X-ray photoelectron spectroscopy and X-ray diffraction. In addition, the electrochemical characterization shows much improved activity for the fabricated h-Ni-MXene-TiO2 regarding water splitting compared to its Ni-MXene-TiO2 counterparts.
Conclusion
This study presents a facile approach for the synthesis of MXenes and paves the way for the use of h-Ni-MXene-TiO2, as a promising catalyst for the water-splitting process.
