Oxygen-Coordinated Single Mn Sites for Efficient Electrocatalytic Nitrate Reduction to Ammonia

Shengbo Zhang; Yuankang Zha; Yixing Ye; Ke Li; Yue Lin; Lirong Zheng; Guozhong Wang; Yunxia Zhang; Huajie Yin; Tongfei Shi; Haimin Zhang

doi:10.1007/s40820-023-01217-z

Oxygen-Coordinated Single Mn Sites for Efficient Electrocatalytic Nitrate Reduction to Ammonia

Nanomicro Lett. 2023 Nov 6;16(1):9. doi: 10.1007/s40820-023-01217-z.

Authors

Shengbo Zhang^{1

2}, Yuankang Zha^{1

2}, Yixing Ye^{1

2}, Ke Li³, Yue Lin⁴, Lirong Zheng⁵, Guozhong Wang^{1

2}, Yunxia Zhang^{1

2}, Huajie Yin^{1

2}, Tongfei Shi^{6

7}, Haimin Zhang^{8

9}

Affiliations

¹ Laboratory of Materials Physics, Centre for Environmental and Energy Nanomaterials, Anhui Key Laboratory of Nanomaterials and Nanotechnology, CAS Center for Excellence in Nanoscience, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei, 230031, People's Republic of China.
² University of Science and Technology of China, Hefei, 230026, People's Republic of China.
³ Key Laboratory of Agricultural Sensors, Ministry of Agriculture, School of Information and Computer, Anhui Agricultural University, Hefei, 230026, People's Republic of China. keli@ahau.edu.cn.
⁴ Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, 230026, People's Republic of China.
⁵ Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing, 100049, People's Republic of China.
⁶ Laboratory of Materials Physics, Centre for Environmental and Energy Nanomaterials, Anhui Key Laboratory of Nanomaterials and Nanotechnology, CAS Center for Excellence in Nanoscience, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei, 230031, People's Republic of China. tfshi@issp.ac.cn.
⁷ University of Science and Technology of China, Hefei, 230026, People's Republic of China. tfshi@issp.ac.cn.
⁸ Laboratory of Materials Physics, Centre for Environmental and Energy Nanomaterials, Anhui Key Laboratory of Nanomaterials and Nanotechnology, CAS Center for Excellence in Nanoscience, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei, 230031, People's Republic of China. zhanghm@issp.ac.cn.
⁹ University of Science and Technology of China, Hefei, 230026, People's Republic of China. zhanghm@issp.ac.cn.

Abstract

Electrocatalytic nitrate reduction reaction has attracted increasing attention due to its goal of low carbon emission and environmental protection. Here, we report an efficient NitRR catalyst composed of single Mn sites with atomically dispersed oxygen (O) coordination on bacterial cellulose-converted graphitic carbon (Mn-O-C). Evidence of the atomically dispersed Mn-(O-C₂)₄ moieties embedding in the exposed basal plane of carbon surface is confirmed by X-ray absorption spectroscopy. As a result, the as-synthesized Mn-O-C catalyst exhibits superior NitRR activity with an NH₃ yield rate (R_NH3) of 1476.9 ± 62.6 μg h^-1 cm^-2 at - 0.7 V (vs. reversible hydrogen electrode, RHE) and a faradaic efficiency (FE) of 89.0 ± 3.8% at - 0.5 V (vs. RHE) under ambient conditions. Further, when evaluated with a practical flow cell, Mn-O-C shows a high R_NH3 of 3706.7 ± 552.0 μg h^-1 cm^-2 at a current density of 100 mA cm^-2, 2.5 times of that in the H cell. The in situ FT-IR and Raman spectroscopic studies combined with theoretical calculations indicate that the Mn-(O-C₂)₄ sites not only effectively inhibit the competitive hydrogen evolution reaction, but also greatly promote the adsorption and activation of nitrate (NO₃^-), thus boosting both the FE and selectivity of NH₃ over Mn-(O-C₂)₄ sites.

Keywords: Atomically dispersed; Hydrogen evolution reaction; In situ spectroscopic studies; Nitrate reduction reaction; Oxygen coordination.