Mesoporous PdN Alloy Nanocubes for Efficient Electrochemical Nitrate Reduction to Ammonia

Abstract

Developing highly active and selective electrocatalysts for electrochemical nitrate reduction reaction (NITRR) is very important for synthesizing recyclable ammonia (NH3) in an economic and environmentally friendly manner. Despite some encouraging progress, their activity and selectivity have been remarkably slower than expected. In this manuscript, mesoporous palladium‐nonmetal (meso‐PdX) nanocubes (NCs) are reported as a new series of highly efficient electrocatalysts for selective nitrate reduction reaction (NITRR) electrocatalysis to NH3. The samples feature uniformly alloyed compositions and highly penetrated mesopores with abundant highly active sites and optimized electronic structures. The best meso‐PdN NCs hold an outstanding NITRR activity and selectivity with a remarkable NH3 Faradaic efficiency of 96.1% and a yield rate of 3760 µg h−1 mg−1, suppressing the state‐of‐the‐art electrocatalysts. Meanwhile, meso‐PdN NCs are electrocatalytically stable, retaining well the activity and selectivity of NO3−‐to‐NH3 electrocatalysis for more than 20 cycles. Detailed mechanism studies ascribe the superior performance to combined compositional and structural synergies of meso‐PdN NCs that not only promote the adsorption (reactivity) of NO3− and the desorption of NH3 but also increase the retention time of key intermediates for the deeper NITRR electrocatalysis to NH3 through an eight‐electron pathway.

Defect engineering of two-dimensional materials for advanced energy conversion and storage

“…337 Ammonia (NH 3 ), as a key intermediate in the nitrogen cycle, has been widely used in modern society, such as in fertilizers, fuel explosives, and clean energy carriers. [338][339][340] Industrial NH 3 production mainly relies on the Haber-Bosch process in a high-temperature and highpressure atmosphere, leading to intensive energy consumption and a vast carbon footprint. [341][342][343] Recently, electrocatalytic strategies have been regarded as green, decarbonized, and efficient routes for decentralized ammonia production.…”

Recent advances in nonmetallic modulation of palladium-based electrocatalysts

“…A widely accepted explanation is that the interactions between the N p and Pd d orbitals might be strongly associated with the structure-activity relationship. As a further example, Guo et al recently demonstrated the synthesis of PdN x nanocrystals (x ≤ 0.5) with controllable stoichiometric via the hydrothermal decomposition of urea to incorporate N atoms into the lattices of Pd nanocubes [Figure 7A] [128] . Corresponding EDS images clearly reveal the effective doping of N atoms.…”

“…Effect of composition proportion and structure design on the electrocatalytic performance of Pd-based nitrides. (A) TEM image of Pd 2 N nanocrystal with inset EDS mappings diagram; (B) ORR polarization curves in 0.1 M KOH of Pd-based nitrides with different nitrogen content and other counterparts; (C) the stability tests of the catalysts in Figure7B; (A-C) reproduced with permission from[128] :Copyright 2021, The Royal Society of Chemistry; (D) diagram of the electrocatalytic mechanism of meso-PdN NCs for selective NO 3 -to -NH 3 electrocatalysis. Reproduced with permission from[129] :Copyright 2022, Wiley-VCH; (E) TEM image of Cu 3 PdN nanocrystals with insert antiperovskite-type Cu 3 PdN structure model; (F) ORR polarization curves of Cu 3 PdN, Cu 3 N, and Pd nanoparticle in 0.1 M KOH; (G) the relation between mass activity and cycle numbers of Cu 3 PdN and Pd; (E-G) reproduced with permission from[130] : Copyright 2014, American Chemical Society.…”

Hierarchical Nanospheres with Polycrystalline Ir&Cu and Amorphous Cu2O toward Energy‐Efficient Nitrate Electrolysis to Ammonia

“…This may lead to the electrochemical reduction of metallic ions and hence catalyst degradation. Besides, it has been proved that the NITRR at large overpotential usually suffers from vigorous competition from hydrogen evolution reaction (HER), [23][24][25][26] which lowers the NH 3 FE. Therefore, it would be advantageous to find catalysts applicable to the NITRR at low overpotentials of ≈0.69 V or working potentials of ≥0 V RHE , where the catalyst degradation and HER occurrence are almost negligible.…”

“…[27][28][29][30][31][32][33] Nevertheless, fewer has been reported for NITRR. [13,21,22,[34][35][36][37][38] In a state-of-the-art work, Chen et al reported a series of noble-metal-dispersed copper nanowires (i.e., M-CuNW, MRu, Os, Rh, Ir) as the catalyst for alkaline NITRR. Among them, the Ru-CuNW exhibited an excellent activity, significantly outperforming all earlier catalysts [13][14][15][16][17][18][19][20][21][22] as well as the reference catalysts including Ir-CuNW.…”