Hierarchical CoS/MoS flower-like heterostructured arrays derived from polyoxometalates for efficient electrocatalytic nitrogen reduction under ambient conditions.

Electrochemical nitrogen reduction reaction (NRR) has been identified as a prospective alternative for sustainable ammonia production. Developing cost-effective and highly efficient electrocatalysts is critical for NRR under ambient conditions. Herein, the hierarchical cobalt-molybdenum bimetallic sulfide (CoS/MoS) flower-like heterostructure assembled from well-aligned nanosheets has been easily fabricated through a one-step strategy. The efficient synergy between different components and the formation of heterostructure in CoS/MoS nanosheets with abundant active sites makes the non-noble metal catalyst CoS/MoS highly effective in NRR, with a high NH yield rate (38.61 μg h mg), Faradaic efficiency (34.66%), high selectivity (no formation of hydrazine) and excellent long-term stability in 1.0 mol L KSO electrolyte (pH = 3.5) at -0.25 V versus the reversible hydrogen electrode (vs. RHE) under ambient conditions, exceeding much recently reported cobalt- and molybdenum-based materials, even catch up with some noble-metal-based catalyst. Density functional theory (DFT) calculation indicates that the formation of NH* species on CoS(200)/MoS(002) is the rate-determining step via both the alternating and distal pathways with the maximum ΔG values (1.35 eV). These results open up opportunities for the development of efficient non-precious bimetal-based catalysts for NRR.