Delicate Tuning of the Ni/Co Ratio in Bimetal Layered Double Hydroxides for Efficient N₂ Electroreduction

Electroreduction of N₂ to NH₃ at ambient conditions using renewable electricity is promising, but developing efficient electrocatalysts is still challenging due to the inertness of N≡N bonds. Layer double hydroxides (LDHs) composed of first-row transition metals with empty d-orbitals are theoretically promising for N₂ electroreduction (NRR) but rarely reported. Herein, hollow NiCo-LDH nanocages with different Ni/Co ratios were prepared, and their electronic structures and atomic arrangements were critical. The synergetic mechanisms of Ni and Co ions were revealed, and the optimized catalytic sites were proposed. Besides, in-situ Raman spectroscopy and ¹⁵ N₂ isotopic labeling studies were applied to detect reaction intermediates and confirm the origin of NH₃ . As a result, high NH₃ yield of 52.8 μg h^-1  mg_cat ^-1 and faradaic efficiency of 11.5 % were obtained at -0.7 V, which are top-ranking among Co/Ni-based NRR electrocatalysts. This work elucidates the structure-activity relationship between LDHs and NRR and is instructive for rational design of LDH-based electrocatalysts.