Modulating the coordination environment of active site structure for enhanced electrochemical nitrogen reduction: The mechanistic insight and an effective descriptor

The effect of coordination environment of active site structure can never be underestimated in the rational design of a high-performance catalyst especially in electrochemical application. We designed a B-modified C2N-based double-atom catalyst (M2@B2-C2N) with the hybrid coordination of B2N4, on which electrochemical nitrogen reduction reaction (NRR) was computationally studied. Our DFT calculations revealed that the NRR could proceed highly efficiently for M2 = Mo2 and W2 with the onset potential of UL = -0.25 V and UL = -0.27 V, respectively. Remarkably, the NRR complied with a special quasi-dissociative mechanism instead of the conventional associative mechanism on M2@B2-C2N (M2 = Mo2 and W2). Using the optimal metal-based catalyst as a reference, these two model catalysts could yield superior NRR selectivity with respect to HER. The AIMD simulation demonstrated that the NRR could proceed with the applied potential of cathode as URHE = -0.20 V (Mo2) and -0.39 V (W2). The underlying chemical and structural origin of coordination environment was formulated as an effective descriptor omega, which enables to bridge the NRR activity and active site structure. Our study could further the understanding of metal active site structure that catalyzes an electrochemical reaction involving small molecules.