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

Developing highly active, non‐noble‐metal H 2 ‐evolution catalysts is appealing yet still remains a great challenge in the field of electrocatalytic and photocatalytic H 2 production. In this work, high quality transition‐metal carbonitrides M 3 CN (MXene) are investigated using well‐defined density functional theory (DFT) calculations. The structural configurations, H‐adsorption free energy (Δ G H ) and charge transfer for bare, surface‐terminated and transition‐metal (TM)‐modified M 3 CNO 2 are systematically studied. The calculated results indicate that all bare transition metal carbonitrides exhibit strong binding between H atom and catalysts. In addition, only Ti 3 CNO 2 and Nb 3 CNO 2 have the potential to be HER active catalysts based on the Δ G 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 Ti 3 CNO 2 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.