Electronic perturbation of Pd single-atom catalysts on graphdiyne derivatives toward effective electrocatalytic nitrate reduction

Abstract

Electrocatalytic reduction of nitrate (NO₃⁻) to ammonia (NH₃) is a promising approach for addressing water pollution caused by nitrate and producing industrial feedstock NH₃. However, a significant challenge lies in effectively suppressing the formation of undesired byproducts such as H₂, N₂, NO₂⁻, and N₂H₄. In this study, three Pd single-atom catalysts (SACs) supported on graphdiyne (GDY) derivatives functionalized with electron-withdrawing and electron-donating groups denoted as Pd/GDY-F, Pd/GDY-H and Pd/GDY-OMe were prepared. Structural characterization showed that due to the electron induction effect of the functional groups, Pd/GDY-F displays the highest Pd valence state, followed by Pd/GDY-H and Pd/GDY-OMe. Interestingly, the nitrate reduction activity also follows the order Pd/GDY-F > Pd/GDY-H > Pd/GDY-OMe, indicating that the nitrate reduction activity of Pd depends on the Pd oxidation state. In addition, the anion exchange ionomers and high nitrate concentrations are beneficial for nitrate reduction. Under optimized conditions, Pd/GDY-F displays a high Faraday efficiency (FE) of 96.2% ± 2.5% toward NH₃. Mechanistic studies revealed that high-valence Pd atoms favor the adsorption of nitrate reduction intermediates, leading to a high Faraday efficiency for NH₃.

Keywords

Electrochemical nitrate reduction / Ammonia synthesis / Single-atom catalyst / Palladium / Graphdiyne

Declaration of Competing Interest

The authors declare the following personal relationships which may be considered as competing interests: Lele Duan is currently employed by Zhejiang Baima Lake Laboratory Co., Ltd. Other authors declare that there are no competing interests.

CRediT authorship contribution statement

Cheng Wang: Writing – original draft, Methodology, Investigation. Tao Song: Validation, Formal analysis. Hao Dai: Investigation. Siyan Shu: Investigation. Shenghan Zhang: Investigation. Hongliang Dong: Investigation. Yongfei Ji: Funding acquisition, Investigation, Writing – original draft. Lele Duan: Writing – review & editing, Supervision, Funding acquisition, Conceptualization.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (22179057, L.D.), start-up package from Westlake University (L.D.), and Natural Science Foundation of Guangdong Province (2023A1515012238). The authors acknowledge the financial support from the Shanghai Key Laboratory of Material Frontiers Research in Extreme Environments (MFree), China (No. 22dz2260800). We acknowledge support from the BL11B and BL13SSW stations at the Shanghai Synchrotron Radiation Facility (SSRF).

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