Orbital symmetry matching: Achieving superior nitrogen reduction reaction over single-atom catalysts anchored on Mxene substrates

The nitrogen reduction reaction (NRR) under ambient conditions is still challenging due to the inertness of N₂. Herein, we report a series of superior NRR catalysts identified by examining Ti₂NO₂ MXenes embedded with 28 different single-atom catalysts using first-principles calculations. The stability of this system was first verified using formation energies, and it is discovered that N₂ can be effectively adsorbed due to the synergistic effect between single atom catalysis and the Ti atoms. Examination of the electronic structure demonstrated that this design satisfies orbital symmetry matching where “acceptor-donor” interaction scenario can be realized. A new “enzymatic-distal” reaction mechanism that is a mixture of the enzymatic and distal pathways was also discovered. Among all of the candidates, Ni anchored on MXene system achieves an onset potential as low as −0.13 V, which to the best of our knowledge is the lowest onset potential value reported to date. This work elucidates the significance of orbital symmetry matching and provides theoretical guidance for future studies.