The electrocatalytic nitrogen reduction reaction (eNRR) is regarded as a promising approach for ammonia synthesis owing to its low energy requirements and environmentally benign, pollution-free benefits. However, existing approaches are hindered by challenges including low ammonia production and inadequate catalyst stability. This study utilized an in situ growth approach to synthesize Gd-doped MIL-101 catalysts, examining the influence of Gd3+ and external magnetic fields on the eNRR activity of these catalysts and elucidating their underlying mechanisms. Results demonstrate that MIL-101-0.25Gd achieves the highest ammonia yield (12.23 μg·h–1·mgcat–1) and Faraday efficiency (9.39%), alongside outstanding structural stability, with only a 14.9% reduction in current density after 100 h of testing. This improvement arises from gadolinium-induced surface roughening and elevated apparent activity. Concurrently, Gd facilitates orbital gradient coupling among the 3d orbitals of Fe, the 2p orbitals of O, and the 4f orbitals of Gd within MIL-101-Fe, thereby expediting the cleavage of the nitrogen triple bond. This enhances the rate of electron transfer in the eNRR, thereby improving its overall performance. At a potential of −1.2 V, the catalyst demonstrated optimal eNRR performance under a static magnetic field of 0.110 T, attaining an ammonia yield of 16.05 μg·h–1·mgcat–1and a Faraday efficiency of 10.76%. These values denote approximately 31.2% and 14.59% enhancements, respectively, in comparison to the nonmagnetized condition. This phenomenon is attributed to the magnetic field facilitating bubble desorption from the catalyst surface, while the Zeeman effect induced by Gd within the magnetic field supplies supplementary energy, consequently reducing the activation energy for eNRR.
Meng et al. (Thu,) studied this question.