Issue 14, 2022

A doping element improving the properties of catalysis: in situ Raman spectroscopy insights into Mn-doped NiMn layered double hydroxide for the urea oxidation reaction

Abstract

Elemental doping has been proved to be an efficient means to adjust the performance of Ni-based hydroxides for the electrochemical urea oxidation reaction. However, the mechanism by which elemental doping affects the catalytic activity of such bimetallic catalysts remains unclear and there is a lack of evidence. Herein, we dope Ni(OH)2 with Mn, a typical dopant, and show that Mn doping reduces the onset potential of Ni hydroxide oxidation, which favors the generation of electrochemically active NiIIIOOH, and increases the electrochemical reversibility of the Ni redox pair in NiMn layered double hydroxides (LDHs). In situ Raman spectroscopy analysis provides direct spectroscopic evidence that Mn promotes the production of high-valence NiIIIOOH, specifically from ca. 0.4 V vs. Hg/HgO for Ni(OH)2 to ca. 0.3 V vs. Hg/HgO for Ni0.2Mn0.8 LDHs, i.e., a negative shift of 100 mV. The Raman spectroscopy results also reveal that Mn doping elongates the Ni–O bond in NiOOH and leads to increased phase structure disorder. Consequently, the UOR performance of Ni1−xMnx LDH surpasses that of Ni(OH)2. This study provides important information and a clear mechanistic explanation for the crucial roles of dopants in bimetallic electrocatalysts.

Graphical abstract: A doping element improving the properties of catalysis: in situ Raman spectroscopy insights into Mn-doped NiMn layered double hydroxide for the urea oxidation reaction

Supplementary files

Article information

Article type
Paper
Submitted
16 févr. 2022
Accepted
25 mai 2022
First published
25 mai 2022

Catal. Sci. Technol., 2022,12, 4471-4485

A doping element improving the properties of catalysis: in situ Raman spectroscopy insights into Mn-doped NiMn layered double hydroxide for the urea oxidation reaction

X. Yang, H. Zhang, W. Xu, B. Yu, Y. Liu and Z. Wu, Catal. Sci. Technol., 2022, 12, 4471 DOI: 10.1039/D2CY00308B

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