Element-dependent effects of alkali cations on nitrate reduction to ammonia

Yida Zhang; Zhentao Ma; Shaokang Yang; Qingyu Wang; Limin Liu; Yu Bai; Dewei Rao; Gongming Wang; Hongliang Li; Xusheng Zheng

doi:10.1016/j.scib.2024.02.011

Element-dependent effects of alkali cations on nitrate reduction to ammonia

Sci Bull (Beijing). 2024 Apr 30;69(8):1100-1108. doi: 10.1016/j.scib.2024.02.011. Epub 2024 Feb 9.

Authors

Yida Zhang¹, Zhentao Ma², Shaokang Yang³, Qingyu Wang¹, Limin Liu², Yu Bai⁴, Dewei Rao³, Gongming Wang⁴, Hongliang Li⁵, Xusheng Zheng⁶

Affiliations

¹ National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China; College of Chemistry and Materials Science, Experimental Center of Engineering and Material Science, University of Science and Technology of China, Hefei 230026, China.
² National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China.
³ School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China.
⁴ College of Chemistry and Materials Science, Experimental Center of Engineering and Material Science, University of Science and Technology of China, Hefei 230026, China.
⁵ National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China; Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China. Electronic address: [email protected].
⁶ National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China. Electronic address: [email protected].

PMID: 38423872
DOI: 10.1016/j.scib.2024.02.011

Abstract

Catalytic conversion of nitrate (NO₃^-) pollutants into ammonia (NH₃) offers a sustainable and promising route for both wastewater treatment and NH₃ synthesis. Alkali cations are prevalent in nitrate solutions, but their roles beyond charge balance in catalytic NO₃^- conversion have been generally ignored. Herein, we report the promotion effect of K⁺ cations in KNO₃ solution for NO₃^- reduction over a TiO₂-supported Ni single-atom catalyst (Ni₁/TiO₂). For photocatalytic NO₃^- reduction reaction, Ni₁/TiO₂ exhibited a 1.9-fold NH₃ yield rate with nearly 100% selectivity in KNO₃ solution relative to that in NaNO₃ solution. Mechanistic studies reveal that the K⁺ cations from KNO₃ gradually bonded with the surface of Ni₁/TiO₂, in situ forming a K-O-Ni moiety during reaction, whereas the Na⁺ ions were unable to interact with the catalyst in NaNO₃ solution. The charge accumulation on the Ni sites induced by the incorporation of K atom promoted the adsorption and activation of NO₃^-. Furthermore, the K-O-Ni moiety facilitated the multiple proton-electron coupling of NO₃^- into NH₃ by stabilizing the intermediates.

Keywords: Alkali cations; Ammonia; Ni single-atom catalyst; Nitrate reduction; Potassium.