Tuning Local Atomic Structures in MoS ₂ Based Catalysts for Electrochemical Nitrate Reduction

Abstract In recent years, there has been a substantial surge in the investigation of transition‐metal dichalcogenides such as MoS ₂ as a promising electrochemical catalyst. Inspired by denitrification enzymes such as nitrate reductase and nitrite reductase, the electrochemical nitrate reduction catalyzed by MoS ₂ with varying local atomic structures is reported. It is demonstrated that the hydrothermally synthesized MoS ₂ containing sulfur vacancies behaves as promising catalysts for electrochemical denitrification. With copper doping at less than 9% atomic ratio, the selectivity of denitrification to dinitrogen in the products can be effectively improved. X‐ray absorption characterizations suggest that two sulfur vacancies are associated with one copper dopant in the MoS ₂ skeleton. DFT calculation confirms that copper dopants replace three adjacent Mo atoms to form a trigonal defect‐enriched region, introducing an exposed Mo reaction center that coordinates with Cu atom to increase N ₂ selectivity. Apart from the higher activity and selectivity, the Cu‐doped MoS ₂ also demonstrates remarkably improved tolerance toward oxygen poisoning at high oxygen concentration. Finally, Cu‐doped MoS ₂ based catalysts exhibit very low specific energy consumption during the electrochemical denitrification process, paving the way for potential scale‐up operations.