Search

The unique combination of high electronic conductivity, surface area, and tunability in MXenes makes them ideal electrocatalysts for the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR); however, existing literature predominantly focuses on their electrocatalytic performance as opposed to their long-term electrocatalytic stability, such as how nitride MXene HER or ORR activity varies over time. A key experiment to understanding the stability is evaluating the overpotential, Tafel slope, and exchange current density of the MXene after prolonged immersion in solvents typically used for MXene storage. Herein, we investigate the electrocatalytic behavior of a nanolayered Ti4N3Tx nitride MXene toward HER and ORR after a period of 230 days in various solvents, including water, ethanol, N–N dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetonitrile, and hexane. Specifically, we evaluate the overpotential, Tafel slope, and limiting current density after the 230 day period as metrics of the material stability and degradation. Remarkably, the HER activity of the nanolayered Ti4N3Tx MXene remains unaltered after 230 days of immersion, with consistent overpotential and Tafel slope values, regardless of the solvent. We observe a minimal amount of TiO2 formation, as suggested by Raman spectroscopy and scanning electron microscopy imaging. However, for ORR, the overpotential, Tafel slope, and limiting current density change after the immersion time. Additionally, in all the solvents, the number of electrons transferred per molecule of product shifts from 4 to 2, indicating a mechanistic change. These findings suggest that the effect of immersion solvent on MXene electrocatalysis is correlated with the type of reaction and is likely a strong function of the terminal group. In summary, these findings can be exploited to establish MXene-solvent electrocatalytic relationships to broaden their utilization in electrocatalysis and facilitate their integration in solvent-based applications. [ABSTRACT FROM AUTHOR]