Ziqiang Wang,Zechuan Dai,Hongjie Yu,Hugang Zhang,Wenjing Tian,You Xu,Xiaonian Li,Liang Wang,Hongjing Wang
Electrochemical ammonia synthesis is considered as an alternative sustainable method to the traditional Haber–Bosch process because of the reduced energy consumption and mild operation conditions. The key is to design efficient electrocatalysts for facile adsorption and activation of nitrogen. Herein, a nanoporous Pd film with a tunable pore size has been in situ grown on Ni foam (nPd/NF) via a micelle-assisted replacement method using NF as a reductant and substrate, where polystyrene-b-poly(ethylene oxide) and 1,3,5-triisopropylbenzene serve as a pore-forming agent and a swelling agent, respectively. Combining the continuous large nanoporous structure and self-supported properties, the obtained nPd/NF exhibits excellent catalytic performance for ammonia synthesis with a high NH3 yield of 18.27 μg h–1 mgcat–1 and a faradaic efficiency of 10.36% in 0.1 M Na2SO4. This work provides a fascinating route for the rational design of self-supported porous noble metals with a tunable pore size for effective electrosynthesis of ammonia.
The electrochemical reduction of NO x to ammonia presents a dual solution to both energy and environmental crises. Despite substantial progress in developing strategies to enhance the efficiency, the design of catalysts and the elucidation of the reaction mechanism remain significant challenges. Herein, we propose that the spin polarization of chiral nanostructured Pd films (CNPFs) can facilitate the formation of triplet 3 NOH by regulating the parallel electron spin alignment. Additionally, the helical lattice distortion of nanostructures can decrease reaction energy of adsorbed intermediates, thereby triggering multiple proton-coupled electron transfer steps to promote the generation ammonia. The CNPFs with helical lattice distorted nanoflakes were fabricated via electrodeposition using methionine as a symmetry-breaking agent. In the electrocatalytic reduction of nitrite to ammonia, the CNPFs achieved a maximum Faradaic efficiency (FE) of 97.6 % for NH 3 at −0.6 V vs. reversible hydrogen electrode. Ammonia was not detected in the nitrite-free electrolyte solution, indicating a direct correlation between the presence of nitrite in the solution and the production of ammonia. This work elucidates the critical roles of spin polarization and helical lattice distortion in the nitrite electroreduction reaction, revealing the underlying mechanisms of reactions involving triplet intermediates.
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