Insights into the Electrocatalytic Hydrogen Evolution Reaction Mechanism on Two-Dimensional Transition-Metal Carbonitrides (MXene)

Developing highly active, non-noble-metal H₂ -evolution catalysts is appealing yet still remains a great challenge in the field of electrocatalytic and photocatalytic H₂ production. In this work, high quality transition-metal carbonitrides M₃ CN (MXene) are investigated using well-defined density functional theory (DFT) calculations. The structural configurations, H-adsorption free energy (ΔG_H ) and charge transfer for bare, surface-terminated and transition-metal (TM)-modified M₃ CNO₂ are systematically studied. The calculated results indicate that all bare transition metal carbonitrides exhibit strong binding between H atom and catalysts. In addition, only Ti₃ CNO₂ and Nb₃ CNO₂ have the potential to be HER active catalysts based on the ΔG_H results. In an attempt to overcome poor HER activity limitations, we apply O as well as OH mixed groups and TMs modification on the Ti₃ CNO₂ surface for tuning HER activity, and a significant improvement of HER activity is observed. Overall, this work presents in-depth investigations for transition-metal carbonitrides (MXene) and opens up new designs for robust metal carbonitrides as noble-metal-free cocatalysts for highly efficient and low-cost MXene-based nanocomposites for water splitting applications.