Interfacial engineering of CoMoO4@MoS2/CoS2 heterostructures for enhanced electrochemical nitrate reduction to ammonia

Abstract

The electrochemical nitrate reduction reaction (e-NO₃RR) to ammonia not only can effectively remove nitrate pollutants but also is a green strategy for ammonia synthesis. However, the conversion of NO₃⁻ into NH₃ involves the generation of some undesired by-products and severe competing hydrogen evolution reactions (HERs), limiting its further development. Herein, a rod-like CoMoO₄@MoS₂/CoS₂ heterostructure with rich interfaces was easily designed via a hydrothermal route, followed by a gas-phase sulfurization method for efficient electrochemical nitrate reduction to NH₃. Benefiting from the interfacial effect, the optimal CoMoO₄@MoS₂/CoS₂-5 heterostructure exhibited an excellent e-NO₃RR performance, with a high NH₃ faradaic efficiency (FE) of 96.11% and an NH₃ yield rate of 0.45 mmol h⁻¹ mg_cat⁻¹ at −0.8 V (vs. RHE), which was superior to those of CoMoO₄ and MoS₂/CoS₂. The validation experiments suggested that the heterointerface can inhibit the generation of by-products and competing HERs, greatly facilitating the hydrogenation process.