Chiral nanostructured Pd films for efficient electrocatalytic reduction of nitrite to 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.