(569co) Complete Nitrate to Ammonia Electrosynthesis Via Nanoconfined Cufe@CuNi Catalysts Unveiling Unique Pathways with Advanced DFT Modelling

The electrocatalytic synthesis of ammonia from nitrate reduction (NO₃−RR) shows great potential in sustainable energy development, especially for agriculture and carbon-free energy supply. The CuFe@CuNi dual-layer layered double hydroxide (LDH) tandem catalyst on nickel foam (NF) was synthesized through a fast and friendly two-step electrodeposition process. This catalyst significantly enhances the NO₃−RR efficiency by addressing the challenge of high reaction overpotential and demonstrating remarkable capabilities. At -1.4V potential it achieves an optimal ammonia production rate of 0.7 mmol h^-1 cm^-2 with completely conversion and selectivity, outperforming the existing catalysts under similar conditions. Furthermore, the catalyst maintains 100% Faraday efficiency (FE) under neutral and acidic conditions, highlighting its exceptional performance across different environments. The high efficiency is attributed to the innovative dual-layer LDH structure that promotes effective electron transfer and increases active catalytic sites. Additionally, this study pioneers a dual-layer LDH model illustrating the novel concept of nanoconfined catalysis. Density functional theory (DFT) analysis coupled with in-situ Raman spectroscopy elucidates the complex mechanisms of NO₃⁻RR based on this model. DFT results reveal a new mechanism within the close proximity (<3 Å's distance between layers) dual-layer LDH structure that facilitates a novel reaction pathway transferring the reaction site resulting in lower energy barrier compared to traditional one-site mechanism. This mechanism enhances NO₃⁻ adsorption while suppressing hydrogen evolution leading to improved efficiency and sustainability in ammonia synthesis. The CuFe LDH layer significantly lowers the energy barrier in the rate-determining step, while the CuNi LDH layer enhances the hydrogenation process, vital for efficient ammonia synthesis. This layered structure's synergistic effect not only reduces reaction energy barriers but also ensures high selectivity for nitrate-to-ammonia conversion. This study offers valuable advancements in the field of electrocatalysis by proposing a strategic approach that improves ammonia production efficiency while considering environmental impact.