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Construction of Defect‐Rich Ni‐Fe‐Doped K 0.23 MnO 2 Cubic Nanoflowers via Etching Prussian Blue Analogue for Efficient Overall Water Splitting
Author(s) -
Liao Huanyun,
Guo Xingzhong,
Hou Yang,
Liang Hao,
Zhou Zheng,
Yang Hui
Publication year - 2020
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201905223
Subject(s) - water splitting , prussian blue , materials science , tafel equation , oxygen evolution , bifunctional , doping , chemical engineering , nanotechnology , catalysis , electrode , chemistry , optoelectronics , electrochemistry , biochemistry , photocatalysis , engineering
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 MnO 2 cubic nanoflowers (Ni‐Fe‐K 0.23 MnO 2 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 MnO 2 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 MnO 2 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||IrO 2 cell at large current density. Density functional theory calculations further confirm that doping Ni and Fe into the crystal lattice of δ‐MnO 2 can not only reinforce the conductivity but also reduces the adsorption free‐energy barriers on the active sites during OER and HER.