Phase-Regulated FeSe2@(1T-2H)-MoSe2 Derived from Anderson-Type Polyoxometalate as an Efficient Electrocatalyst for the Nitrogen Reduction Reaction

The ambient electrolytic nitrogen reduction reaction (e-NRR) has been extensively studied as a potential alternative to the capital and energy-intensive Haber–Bosch process for ammonia production. However, the design and construction of highly effective catalysts for e-NRR are still extremely challenging. In this work, a series of phase-regulated composites FeSe2@(1T-2H)-MoSe2-X (X represents the reaction time of 4, 6, and 8 h) were designed and synthesized by using the Anderson-type polyoxometalate as a preassembly platform, together with phase engineering. The progressive transformation from 2H-MoSe2 to 1T-MoSe2 can be implemented in FeSe2@(1T-2H)-MoSe2-X by inserting Fe and changing the reaction time. The electrocatalytic performances have been significantly improved thanks to the synergistic effect of FeSe2, 2H-MoSe2, and 1T-MoSe2, which gives rise to a very high electron transfer capability and more active sites. In particular, composite FeSe2@(1T-2H)-MoSe2-6 h (with 69.7% of 1T-MoSe2 and 29.3% of 2H-MoSe2) exhibits an optimal NH3 yield rate of 28.31 μg h–1 mgcat–1 and a Faradaic efficiency of 32.01%. Density functional theory calculations show that multiphasic FeSe2@(1T-2H)-MoSe2-6 h with appropriate content of 1T-MoSe2 can significantly reduce the energy of the rate-determining step (*N2 to *N2H) and inhibit the process of the hydrogen evolution reaction, thereby further increasing the production of NH3.