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Synthesis of hierarchical transition metal oxyhydroxides in aqueous solution at ambient temperature and their application as OER electrocatalysts

Synthesis of hierarchical transition metal oxyhydroxides in aqueous solution at ambient temperature and their application as OER electrocatalysts

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CHEN, Zongkun, Xingkun WANG, Sascha KESSLER, Qiqi FAN, Minghua HUANG, Helmut CÖLFEN, 2022. Synthesis of hierarchical transition metal oxyhydroxides in aqueous solution at ambient temperature and their application as OER electrocatalysts. In: Journal of Energy Chemistry. Elsevier. 71, pp. 89-97. ISSN 2095-4956. Available under: doi: 10.1016/j.jechem.2022.02.042

@article{Chen2022Synth-57759, title={Synthesis of hierarchical transition metal oxyhydroxides in aqueous solution at ambient temperature and their application as OER electrocatalysts}, year={2022}, doi={10.1016/j.jechem.2022.02.042}, volume={71}, issn={2095-4956}, journal={Journal of Energy Chemistry}, pages={89--97}, author={Chen, Zongkun and Wang, Xingkun and Kessler, Sascha and Fan, Qiqi and Huang, Minghua and Cölfen, Helmut} }

Cölfen, Helmut Kessler, Sascha Fan, Qiqi Chen, Zongkun Synthesis of hierarchical transition metal oxyhydroxides in aqueous solution at ambient temperature and their application as OER electrocatalysts Wang, Xingkun Wang, Xingkun Kessler, Sascha 2022 First-row (3d) transition metal oxyhydroxides have attracted increasing attention due to their various advantages. Although investigating the oxidation mechanism and processing such materials into hierarchical architectures are greatly desired for their further development, it remains unclear how the oxidation state change occurs, and efforts to produce hierarchical oxyhydroxides in compliance with high ecological and economic standards have progressed slowly. Here, we describe a facile one-step coprecipitation route for the preparation of hierarchical CoOOH, NiOOH and MnOOH, which involves the diffusion of NH<sub>3</sub> originating from ammonium hydroxide solution into an aqueous solution containing metal ion salts and K<sub>2</sub>S<sub>2</sub>O<sub>8</sub>. Comprehensive characterizations by scanning electron microscope, transmission electron microscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy and in situ pH measurement demonstrated that K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> induces the oxidation state change of metal ion species after the start of hydrolysis. Meanwhile, it was found that, benefiting from the OH<sup>–</sup> concentration gradient created by the NH<sub>3</sub> diffusion method and the suitable growth environment provided by the presence of K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> (high nucleation rate and secondary nucleation), the formation of hierarchical oxyhydroxide structures can be realized in aqueous solution at ambient temperature without the use of heat energy and additional structure-directing agents. The hierarchical CoOOH structures are performed as the electrocatalysts for the oxygen evolution reaction in alkaline media, which exhibit good activity with an overpotential of 320 mV at 10 mA cm<sup>−2</sup> and a low Tafel slope of 59.6 mV dec<sup>–1</sup>, outperforming many congeneric electrocatalysts. Overall, our study not only provides important insights to understand the formation mechanism of hierarchical oxyhydroxides, but also opens up new opportunities for the preparation of hierarchical oxyhydroxides via a facile, green and low-cost method. eng 2022-06-09T13:37:41Z Chen, Zongkun Cölfen, Helmut Fan, Qiqi 2022-06-09T13:37:41Z Huang, Minghua Huang, Minghua

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