Redox reaction of the intercalated proton is the key process of the pseudocapacitive behavior in MXene in H2SO4. The proton’s motion coupling with the co-intercalated water at the electrochemical interface determines the rate performance of MXene pseudocapacitor. However, the atomic-level understanding of proton transfer mechanism in MXene coupling with confined water molecules is not clear yet. Here, we applied the first-principle simulation to reveal the proton transfer mechanism in Ti3C2O2 MXene with the confined water. First, our DFT calculation indicated that the proton is hard to diffuse either through the layer or directly on the surface. Then, the first-principle molecular dynamics (AIMD) simulation was used to further explore the proton transfer mechanism in explicit water solvent. AIMD trajectory showed that the proton transfer between different surface -O sites can occur through the water molecule by forming hydronium ion. Moreover, the proton’s adsorption/desorption rate and diffusivity were found to be dependent on the water layer number between MXene: the more layers of confined water lead to the lower surface reaction rate, but better diffusivity. Then, by detail investigating the non-transfer period, we found in the confine water, proton mobility still follows the Zundel-Eigen-Zundel mechanism as the previous study proposed for bulk water.

Understanding proton transfer in MXene-confined water from first principles

2019 Fall National Meeting

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