Tuning Local Atomic Structures in MoS₂ Based Catalysts for Electrochemical Nitrate Reduction

In recent years, there has been a substantial surge in the investigation of transition-metal dichalcogenides such as MoS₂ as a promising electrochemical catalyst. Inspired by denitrification enzymes such as nitrate reductase and nitrite reductase, the electrochemical nitrate reduction catalyzed by MoS₂ with varying local atomic structures is reported. It is demonstrated that the hydrothermally synthesized MoS₂ 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 MoS₂ 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 N₂ selectivity. Apart from the higher activity and selectivity, the Cu-doped MoS₂ also demonstrates remarkably improved tolerance toward oxygen poisoning at high oxygen concentration. Finally, Cu-doped MoS₂ based catalysts exhibit very low specific energy consumption during the electrochemical denitrification process, paving the way for potential scale-up operations.