Journal
SMALL
Volume 16, Issue 10, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/smll.201905223
Keywords
cubic nanoflowers; defect-rich K0; 23MnO; doping effect; overall water splitting; Prussian blue analogues
Categories
Funding
- National Natural Science Foundation of China [21875217, 51372225]
- Open Project Fund of State Key Laboratory of Silicon Materials [SKL2019-04]
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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 K0.23MnO2 cubic nanoflowers (Ni-Fe-K0.23MnO2 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-K0.23MnO2 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-K0.23MnO2 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 delta-MnO2 can not only reinforce the conductivity but also reduces the adsorption free-energy barriers on the active sites during OER and HER.
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