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.