Unveiling the underlying mechanism of nitrogen fixation by a new class of electrocatalysts two-dimensional TM@g-C4N3 monosheets

The potential of TM atoms embedded g-C4N3 as a new class of electrocatalysts (TM@g-C4N3, TM = 3d, 4d and 5d transition metal) towards nitrogen reduction reaction (NRR) were systematically investigated through the combination of high-throughput screening and first-principles calculations. Among 30 candidate materials, TM@g-C4N3 (TM = V, Tc, Os, Pt) exhibited the highest activity for electrocatalytic N2 reduction to produce NH3. Particularly, V@g-C4N3 is identified as the most active catalyst for NRR with onset potential of -0.37 V. Interestingly, a volcano curve between Uonset (onset potential) and Delta Eads(*N2) (the adsorption energy of N2) is established, and thus Delta Eads(*N2) can be used as a descriptor to characterize the activity of catalysts. Among all investigated catalysts, the lowest onset potential of V@g-C4N3 can be attributed to its moderate adsorption energies for N2. After in-deep analysis of the intrinsic properties of the four catalysts, we found that the increasing order of catalytic activity is consistent with the increasing order of d-band center (epsilon d) of the four catalysts. In addition, the excellent thermal stability of the four catalysts is verified via simulated annealing at 500 K for 10 ps. Furthermore, three catalysts TM@g-C4N3 (TM = V, Tc, Pt) demonstrate good selectivity. Therefore, V@g-C4N3 is a promising electrocatalyst for NRR. Our work opens the way for g-C4N3 as a new type of support to construct efficient single-atom catalyst for electrocatalytic ammonia synthesis. The predicted TM@gC4N3 catalysts will provide useful guidance for experimental synthesis and rational design of catalysts in future.

Automated summary

Through high-throughput screening and first-principles calculations, TM@g-C4N3 (V, Tc, Os, Pt) were identified as a new class of highly active electrocatalysts for nitrogen reduction reaction, with V@g-C4N3 exhibiting the best performance with the lowest onset potential. The relationship between onset potential and adsorption energy of nitrogen was established, providing valuable insights for the rational design and synthesis of catalysts in the future.