Design of single-atom catalysts on S-functionalized Mxenes for enhanced activity and selectivity in N2 electroreduction

Design of high-performance catalysts is one of the key research focuses in electrochemical nitrogen reduction reaction (NRR). Single atom catalysts (SACs) hosted by a suitable template can be a potential candidate for NRR. Recently, two-dimensional (2D) S-functionalized Ti2C (Ti2CS2) and Nb2C (Nb2CS2) MXenes have been successfully synthesized. Here, we screen 18 different single metal atoms on these S-functionalized MXenes by examining their NRR activity and selectivity using the state-of-the-art density functional theory calculations. The calculated free energy change between the first H+/e- pair reduction step and the last H+/e- pair reduction step suggests that Mo@MXene, Nb@MXene and V@MXene are the suitable candidates. The calculation results further reveal that V and Nb on Ti2CS2 and Nb2CS2 weaken the *N adsorption, leading to an enhanced performance in NRR. Our analyses on the electronic properties, structural stability as well as HER indicate that Mo@Nb2CS2 system overall is a highly promising NRR catalyst. The present work provides an interesting route to design SACs based on the S-functionalized MXenes.

Automated summary

Designing high-performance catalysts is a crucial focus in electrochemical nitrogen reduction reaction (NRR), and single atom catalysts (SACs) hosted by suitable templates have potential for NRR. Recently, two-dimensional (2D) S-functionalized Ti2C (Ti2CS2) and Nb2C (Nb2CS2) MXenes have been successfully synthesized. In this study, we used density functional theory calculations to screen 18 different single metal atoms on these S-functionalized MXenes for their NRR activity and selectivity. The calculations suggest that Mo@MXene, Nb@MXene and V@MXene are the suitable candidates, and V and Nb on Ti2CS2 and Nb2CS2 weaken *N adsorption, leading to enhanced performance in NRR. Our analysis indicates that the Mo@Nb2CS2 system is a highly promising NRR catalyst. This work provides an interesting approach for designing SACs based on S-functionalized MXenes.