(665f) Effect of Delamination Chemistry on Electrochemical Reduction Reactions of Ti4N3 nitride Mxene

MXenes, a class of two-dimensional (2D) carbides and nitrides, have been used for many electrochemical reduction reactions owing to their electronic conductivity, specific surface area, and tunable surface chemistry. The performance of MXenes in catalyzing these reactions, specifically hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), is heavily dependent on the aforementioned properties, especially the surface chemistry. Currently, there are limited works that modulate the surface chemistry of nitride MXenes. In this presentation, I will present the effects of termination group modulation on the HER and ORR activity and stability of Ti₄N₃ nitride MXene in alkaline medium. The Ti₄N₃ MXene was synthesized via molten salt etching and delaminated using four different delamination agents namely tetramethylammonium hydroxide (TMAOH), dimethyl sulfoxide (DMSO), water (H₂O), and tetrabutylammonium hydroxide (TBAOH). Findings from FTIR show that all have -O-, -OH, and -F terminations but EDS and XPS show that DMSO-delaminated Ti₄N₃ has higher -F coverage, whereas TMAOH, TBAOH, and H₂O-delaminated Ti₄N₃ have predominantly oxygen terminations, -O- and -OH. In terms of HER activity, the delamination process does not affect onset potential as all had an onset close to -0.50 V vs RHE. However, after 18 hours of chronopotentiometry, the HER performance of each Ti₄N₃ material increased differently – H₂O > TBAOH = TMAOH > DMSO. We attribute this to the predominant -O- and -OH basal plane coverage which act as the HER active sites. For ORR activity, DMSO-delaminated Ti₄N₃ had the most positive onset at 0.78 V and the greatest current retention with 83.6% after 18 hours chronoamperometry. This is in agreement with computational data of other MXene catalysts, where ORR favors MXenes with higher -F surface coverage. These results provide a framework for the exploration of the surface tuning of nitride MXenes for its advancement in fuel cell and water splitting applications.