Spinel oxides are considered as promising low-cost non-precious metal electrocatalysts for oxygen evolution reaction (OER) due to their desirable catalytic activities and fast kinetics. However, as a result of the structural complexity of spinel oxides, systematic and in-depth studies on enhancing the OER performance of spinel oxides remain inadequate. In particular, the construction of active sites regarding the large number of unoccupied octahedral interstices has not yet been explored. Herein, more octahedral sites with high OER activities are constructed on the surface of spinel oxides via a cationic misalignment, which is induced by the defects in the spinel oxide solutions, i.e., MoFe 2 O 4 and CoFe 2 O 4 nanosheets supported on an iron foam (MCFO NS/IF). With increased active sites and modified electronic structure, the state-of-the-art electrocatalyst exhibits the excellent OER catalytic activity with an onset potential of 1.41 V versus RHE and an overpotential of 290 mV to achieve a current density of 500 mA cm −2 . Moreover, such an electrocatalyst also demonstrates fast kinetics with the Tafel slope of 38 mV dec −1 and superior durability by maintaining the OER activity at 250 mA cm −2 for 1000 h.
Tuning electronic
structures through heteroatom doping to weaken
the Mo–H binding strength and constructing larger specific
surface areas are considered an effective strategy to improve the
hydrogen evolution reaction (HER) activity on β-Mo2C in full pH range. In this report, a CH4 (10%)/H2 inducing universal method for the formation of heteroatom-doped
(F, N, S, or B) β-Mo2C nanoparticles (NPs) with nanosized
and clean surface supported on reduced graphene oxide (rGO) (Mo2E
x
C1–x
/rGO, E = F, N, S, or B) is proposed. Doping with different
heteroatoms introduced different promoting effects on Mo2C toward HER in the full pH range. The Mo2F
x
C1–x
/rGO electrocatalysts
show the best activity for HER in acidic, alkaline, and neutral media,
with the onset overpotentials of 37, 45, and 105 mV, respectively,
which achieve 10 mA cm–2 at overpotentials of only
95 mV in 1 M HClO4. More noteworthy is the fact that the
Mo2F
x
C1–x
/rGO electrocatalysts only require 232 and 397 mV
of overpotentials to reach 400 mA cm–2 in acidic
and alkaline solutions, respectively. Besides, the Mo2F
x
C1–x
/rGO
electrocatalysts only need 480 mV of overpotential to reach 200 mA
cm–2 in neutral conditions. Meanwhile, larger specific
surface areas with nanosized and clean surfaces also contribute to
improving the performance of HER, especially Mo2F
x
C1–x
/rGO.
However, the promoting effect of HER by tuning the electronic structures
through doping of B and S into Mo2C is very limited. Moreover,
doped Mo2C-based electrocatalysts in this work show superior
stabilities for HER in the full pH range.
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