Selective electrosynthesis of hydroxylamine from aqueous nitrate/nitrite by suppressing further reduction.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39532869.
- Also identified by DOI 10.1038/s41467-024-54204-2 and PMC identifier 11557954.
- Licence recorded as CC BY-NC-ND.
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Abstract
The electrocatalytic reduction of nitrogenous waste offers a sustainable approach to producing nitrogen-containing chemicals. The selective synthesis of high-value hydroxylamine (NH<sub>2</sub>OH) is challenging due to the instability of NH<sub>2</sub>OH as an intermediate. Here, we present a rational electrocatalyst design strategy for promoting NH<sub>2</sub>OH electrosynthesis by suppressing the competing pathways of further reduction. We screen zinc phthalocyanines (ZnPc) with a high energy barrier for NH<sub>2</sub>OH reduction by regulating their intrinsic activity. Additionally, we discover that carbon nanotube substrates exhibit significant NH<sub>3</sub>-producing activity, which can be effectively inhibited by the high coverage of ZnPc molecules. In-situ characterizations reveal that NH<sub>2</sub>OH and HNO are generated as intermediates in nitrate reduction to NH<sub>3</sub>, and NH<sub>2</sub>OH can be enriched in the ZnPc electrode. In the H-cell, the optimized ZnPc catalyst demonstrates a Faradaic efficiency (FE) of 53 ± 1.7% for NH<sub>2</sub>OH with a partial current density exceeding 270 mA cm<sup>-2</sup> and a turnover frequency of 7.5 ± 0.2 s<sup>-1</sup>. It also enables the rapid electrosynthesis of cyclohexanone oxime from nitrite with a FE of 64 ± 1.0%.