Construction of Defect-Rich Ni-Fe-Doped K0.23 MnO2 Cubic Nanoflowers via Etching Prussian Blue Analogue for Efficient Overall Water Splitting

Huanyun Liao; Xingzhong Guo; Yang Hou; Hao Liang; Zheng Zhou; Hui Yang

doi:10.1002/smll.201905223

Construction of Defect-Rich Ni-Fe-Doped K_0.23 MnO₂ Cubic Nanoflowers via Etching Prussian Blue Analogue for Efficient Overall Water Splitting

Small. 2020 Mar;16(10):e1905223. doi: 10.1002/smll.201905223. Epub 2020 Feb 12.

Authors

Huanyun Liao¹, Xingzhong Guo¹, Yang Hou², Hao Liang¹, Zheng Zhou¹, Hui Yang^{1

3}

Affiliations

¹ State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, P. R. China.
² Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, P. R. China.
³ Zhejiang-California International Nanosystems Institute, Zhejiang University, Hangzhou, 310058, P. R. China.

PMID: 32049431
DOI: 10.1002/smll.201905223

Abstract

Designing elaborate nanostructures and engineering defects have been promising approaches to fabricate cost-efficient electrocatalysts toward overall water splitting. In this work, a controllable Prussian-blue-analogue-sacrificed strategy followed by an annealing process to harvest defect-rich Ni-Fe-doped K_0.23 MnO₂ cubic nanoflowers (Ni-Fe-K_0.23 MnO₂ CNFs-300) as highly active bifunctional catalysts for oxygen and hydrogen evolution reactions (OER and HER) is reported. Benefiting from many merits, including unique morphology, abundant defects, and doping effect, Ni-Fe-K_0.23 MnO₂ CNFs-300 shows the best electrocatalytic performances among currently reported Mn oxide-based electrocatalysts. This catalyst affords low overpotentials of 270 (320) mV at 10 (100) mA cm^-2 for OER with a small Tafel slope of 42.3 mV dec^-1 , while requiring overpotentials of 116 and 243 mV to attain 10 and 100 mA cm^-2 for HER respectively. Moreover, Ni-Fe-K_0.23 MnO₂ CNFs-300 applied to overall water splitting exhibits a low cell voltage of 1.62 V at 10 mA cm^-2 and excellent durability, even superior to the Pt/C||IrO₂ cell at large current density. Density functional theory calculations further confirm that doping Ni and Fe into the crystal lattice of δ-MnO₂ can not only reinforce the conductivity but also reduces the adsorption free-energy barriers on the active sites during OER and HER.

Keywords: Prussian blue analogues; cubic nanoflowers; defect-rich K0.23MnO; doping effect; overall water splitting.

Abstract

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