Exposure of Definite Palladium Facets Boosts Electrocatalytic Nitrogen Fixation at Low Overpotential

Abstract Various electrocatalyst adjustment methods have been reported with the efforts of plenty of researchers, such as element doping, defect, control crystalline phase, surface modification, etc. However, systematic studies on the relationship between the facets of electrocatalysts and the activity of NRR have not been reported. Pd nanocrystals are systematically studied herein, which selectively expose the (100) facet, (111) facet, and (110) facet (each of which behaves as a cube, octahedron, and rhombic dodecahedron) for NRR at mild conditions. Experimental data show that the NH₃ yield of Pd cubes is 24.3 μg mg^‐1_cat h^‐1 at 0 V vs reversible hydrogen electrode and the Faradaic efficiency is 36.6% in 0.1 m Li₂SO₄ electrolyte, which are 2.7 and 5.3 times higher than Pd octahedrons and Pd rhombic dodecahedrons. Meanwhile, it is also one of the best catalytic materials to realize high activity at low overpotentials ever reported. Furthermore, Pd cubes show extraordinary stability for NRR after a long‐time stability test. Density functional theory calculations reveal the remarkable NRR performance of Pd (100) can be attributed to the lower energy barrier of *NNH generation and the lower energy barrier for producing NH₃ from *NH₃ (the rate determining step).