Heterostructured CoS₂/MoS₂ with a Rich Active Site for an Efficient Electrochemical Nitrate Reduction Reaction to Ammonia

The electrochemical nitrate reduction reaction (NO3-RR) has an important application value in realizing efficient synthesis of ammonia (NH3) from NO3-, and obtaining a high-performance and low-cost electrocatalyst is the key. Nonetheless, a majority of the existing catalysts for the NO3-RR have the problem of an unsatisfactory NH3 yield and insufficient stability. Herein, a heterostructured CoS2/MoS2 electrocatalyst is designed and fabricated, and the structure-activity relationship is studied. In comparison to pure CoS2 and MoS2, CoS2/MoS2 demonstrates an enhanced performance with 2.8 and 2.0 times the current enhancement, respectively, at an applied potential of -0.25 V versus reversible hydrogen electrode. It is found that the electronic structure of CoS2/MoS2 is modified through electron transfer between Co and Mo for enhanced reaction dynamics. Moreover, in heterostructured CoS2/MoS2, the two components (CoS2 and MoS2) cooperate well with each other to tailor reaction steps of the NO3-RR. Eventually, CoS2/MoS2 achieves a faradaic efficiency of 97.07%, NH3 yield rate of 0.44 mmol h(-1) cm(-2), NO3- conversion rate of 75.43%, and NH3 selectivity of 95.45% in a 1.0 M KOH electrolyte with 600 ppm of NO3--N, retaining its promising applications in the NO3-RR.