Bimetallic compounds such as hydrotalcite-type layered double hydroxides (LDHs) are promising electrocatalysts owing to their unique electronic structures. However, their abilities toward nitrogen adsorption and reduction are undermined since the surface-mantled, electronegative –OH groups hinder the charge transfer between transition metal atoms and nitrogen molecules. Herein, a smart interfacing strategy is proposed to construct a coupled heterointerface between LDH and 2D g-C₃N₄, which is proven by density functional theory (DFT) investigations to be favorable for nitrogen adsorption and ammonia desorption compared with neat LDH surface. The interfaced LDH and g-C₃N₄ is further hybridized with a self-standing TiO₂ nanofibrous membrane (NM) to maximize the interfacial effect owing to its high porosity and large surface area. Profited from the synergistic superiorities of the three components, the LDH@C₃N₄@TiO₂ NM delivers superior ammonia yield (2.07 × 10⁻⁹ mol s⁻¹ cm⁻²) and Faradaic efficiency (25.3%), making it a high-efficiency, noble-metal-free catalyst system toward electrocatalytic nitrogen reduction.

The advancement of electrocatalytic N₂ reduction reaction (NRR) toward ambient NH₃ synthesis lies in the development of more affordable electrocatalysts than noble metals. Recently, various nanostructures of transition metal compounds have been proposed as effective electrocatalysts; however, they exist in the form of loose powders, which have to be immobilized on a matrix before serving as the electrode for electrolysis. The matrix, being it carbon paper, carbon cloth or metal foam, is electrocatalytically inactive, whose introduction inevitably raises the invalid weight while sacrificing the active sites of the electrode. Herein, we report on the fabrication of a flexible ZrO₂ nanofibrous membrane as a novel, self-supported electrocatalyst. The heteroatom doping can not only endow the nanofibrous membrane with excellent flexibility, but also induce oxygen vacancies which are responsible for easier adsorption of N₂ on the ZrO₂ surface. To improve the electrocatalytic activity, a facile SILAR approach is employed to decorate it with CdS quantum dots (QDs), thereby tuning its Fermi level. To improve the conductivity, a g-C₃N₄ nanolayer is further deposited which is both conductive and active. The resulting hierarchically structured, self-supported electrocatalyst, consisting of g-C₃N₄ encapsulated ZrO₂ nanofibrous membrane decorated with CdS QDs, integrates the merits of the three components, and exhibits a remarkable synergy toward NRR. Excellent NH₃ yield of 6.32 × 10^-10 mol·s^-1·cm^-2 (-0.6 V vs. RHE) and Faradaic efficiency of 12.9% (-0.4 V vs. RHE) are attained in 0.1 M Na₂SO₄.