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Lewis acid–dominated aqueous electrolyte acting as co-catalyst and overcoming N 2 activation issues on catalyst surface
Proceedings of the National Academy of Sciences of the United States of America ( IF 9.4 ) Pub Date : 2022-08-08 , DOI: 10.1073/pnas.2204638119
Ashmita Biswas 1 , Samadhan Kapse 2 , Bikram Ghosh 1 , Ranjit Thapa 2 , Ramendra Sundar Dey 1
Affiliation  

The growing demands for ammonia in agriculture and transportation fuel stimulate researchers to develop sustainable electrochemical methods to synthesize ammonia ambiently, to get past the energy-intensive Haber-Bosch process. However, the conventionally used aqueous electrolytes limit N 2 solubility, leading to insufficient reactant molecules in the vicinity of the catalyst during electrochemical nitrogen reduction reaction (NRR). This hampers the yield and production rate of ammonia, irrespective of how efficient the catalyst is. Herein, we introduce an aqueous electrolyte (NaBF 4 ), which not only acts as an N 2 -carrier in the medium but also works as a full-fledged “co-catalyst” along with our active material MnN 4 to deliver a high yield of NH 3 (328.59 μg h −1 mg cat −1 ) at 0.0 V versus reversible hydrogen electrode. BF 3 -induced charge polarization shifts the metal d-band center of the MnN 4 unit close to the Fermi level, inviting N 2 adsorption facilely. The Lewis acidity of the free BF 3 molecules further propagates their importance in polarizing the N≡N bond of the adsorbed N 2 and its first protonation. This push-pull kind of electronic interaction has been confirmed from the change in d-band center values of the MnN 4 site as well as charge density distribution over our active model units, which turned out to be effective enough to lower the energy barrier of the potential determining steps of NRR. Consequently, a high production rate of NH 3 (2.45 × 10 −9 mol s −1 cm −2 ) was achieved, approaching the industrial scale where the source of NH 3 was thoroughly studied and confirmed to be chiefly from the electrochemical reduction of the purged N 2 gas.

中文翻译:

以路易斯酸为主的含水电解质充当助催化剂并克服催化剂表面的 N 2 活化问题

农业和运输燃料对氨的需求不断增长,促使研究人员开发可持续的电化学方法在环境中合成氨,以通过能源密集型的 Haber-Bosch 过程。然而,常规使用的水性电解质限制 N2个溶解度,导致在电化学氮还原反应(NRR)期间催化剂附近的反应物分子不足。无论催化剂的效率如何,这都会阻碍氨的产率和生产率。在这里,我们介绍了一种水性电解质(NaBF4个), 它不仅充当 N2个- 介质中的载体,但也与我们的活性材料 MnN 一起作为成熟的“助催化剂”4个提供高产量的 NH3个(328.59 微克·小时−1毫克 −1) 在 0.0 V 对可逆氢电极。高炉3个-感应电荷极化移动了 MnN 的金属 d 带中心4个单位接近费米能级,邀请 N2个容易吸附。游离 BF 的路易斯酸度3个分子进一步传播它们在极化吸附的 N 的 N≡N 键中的重要性2个和它的第一次质子化。这种推挽式的电子相互作用已经从 MnN 的 d 波段中心值的变化中得到证实4个站点以及我们活动模型单元上的电荷密度分布,事实证明这足以有效地降低 NRR 潜在决定步骤的能垒。因此,NH 的高产率3个(2.45 × 10−9摩尔−1厘米−2) 实现了,接近 NH 来源的工业规模3个被彻底研究并确认主要来自吹扫的 N 的电化学还原2个气体。
更新日期:2022-08-08
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