Chalcogenide Vacancy-Rich Exfoliated Transition Metal Dichalcogenides as an Efficient Electrocatalyst/Photo-Electrocatalyst for Green Ammonia Production

The catalytic conversion of N 2 gas and NO 3 - ions into ammonia at ambient conditions through electrochemical and photoelectrochemical pathways offers an attractive alternative to the energy-intensive and high-carbon featuring Haber-Bosch process. Therefore, developing highly active, product-selective catalysts with good durability in a cost-effective manner is highly desirable. In this context, we studied vacancy-rich transition metal dichalcogenides for electrochemical NRR and NO 3 RR to produce ammonia. The sulfur vacancy-rich ex-MoS 2 demonstrated a high Faradaic efficiency of 69% with an ammonia yield rate of 5.56 mmol g cat –1 h –1 during electrolysis without a light source, which increased to 80% with a yield of 7.48 mmol g cat –1 h –1 under visible light illumination towards NO 3 RR. Similarly, selenium vacancy-rich ex-MoSe 2 achieved a Faradaic efficiency of 93.6% and a yield rate of 4.9 mmol gcat -1 h -1 during NO 3 RR. Additionally, ex-MoSe 2 showed an NH 3 yield rate of 933 μmol g cat –1 h –1 and an F.E. of 9.39%, while ex-WSe 2 reached 7.22% F.E. and a yield rate of 753 μmol g cat –1 h –1 towards NRR. DFT calculations support the binding of N 2 and NO 3 - species to the vacancies in these dichalcogenides, leading to the formation of *N, which is subsequently reduced to ammonia. Reference: Soloveichik, G., Electrochemical Synthesis of Ammonia as a Potential Alternative to the Haber–Bosch Process. Catal. 2019, 2 (5), 377-380. Qing, G.; Ghazfar, R.; Jackowski, S. T.; Habibzadeh, F.; Ashtiani, M. M.; Chen, C. P.; Smith III, M. R.; Hamann, T. W., Recent Advances and Challenges of Electrocatalytic N 2 Reduction to Ammonia. Chem. Rev. 2020, 120 (12), 5437-5516. Guragain, M.; Kafle, A.; Adesope, Q.; Altafi, M. K.; Amagbor, S. C.; Mesilov, V.; Kelber, J. A.; Cundari, T. R.; D’Souza, F., Photoenhanced Electrochemical Conversion of Nitrate to Ammonia via Sulfur Vacancy-Rich Exfoliated MoS 2 . ACS Catal. 2024 , 18085-18094. Guragain, M.; Kafle, A.; Adesope, Q.; Kularathne, P. P.; Gharaee, M., Sapkota, B.; Yan, H.; Kelber, J. A.; Cundari, T. R. and D’Souza, F., Boosting the Electrocatalytic Dinitrogen Reduction Reaction with Selenium Vacancy in Transition Metal Dichalcogenides, Energy Fuels 2025 , 39, 7, 3619-3626. Kularathne, P. P.; Kafle, A.; Gharaee, M.; Mudiyanselage, R. N. R.; Guragain, M.; Adesope, Q.; Kelber, J. A.; Cundari, T. R. and D’Souza, F., Selective Ammonia Synthesis via Electrocatalytic Nitrate Reduction Reaction on Molybdenum Selenide with Selenium Vacancy, Energy Fuels 2025 , 39 (36), 17543-17551.