Metal (Ni, Co or Fe) foams can be in situ converted into metal sulfide (Ni3S2, Co9S8 or FeS) foams with surface grown N-doped carbon nanotube arrays, and work as efficient superaerophobic electrocatalysts for overall water splitting.
Ni-/Fe-based
materials are promising electrocatalysts for the oxygen
evolution reaction (OER) but usually are not suitable for the hydrogen
evolution reaction (HER). Herein, a durable and bifunctional catalyst
consisting of Ni-FeO
x
and FeNi3 is prepared on nickel foam (Ni-FeO
x
/FeNi3/NF) by in situ solution combustion and subsequent
calcination to accomplish efficient alkaline water splitting. Density
functional theory (DFT) calculation shows that the high HER activity
is attributed to the strong electronic coupling effects between FeO
x
and FeNi3 in the Janus nanoparticles
by modulating ΔG
H* and electronic
states. Consequently, small overpotentials (η) of 71 and 272
mV in HER and 269 and 405 mV in OER yield current densities (j) of 50 and 1000 mA cm–2, respectively.
The catalyst shows outstanding stability for 280 and 200 h in HER
and OER at a j of ∼50 mA cm–2. Also, the robustness and mechanical stability of the electrode
at an elevated j of ∼500 mA cm–2 are excellent. Moreover, Ni-FeO
x
/FeNi3/NF shows excellent water splitting activities as a bifunctional
catalyst as exemplified by j of 50 and 500 mA cm–2 at cell voltages of 1.58 and 1.80 V, respectively.
The Ni-FeO
x
/FeNi3/NF structure
synthesized by the novel, simple, and scalable strategy has large
potential in commercial water electrolysis, and the in situ combustion method holds great promise in the fabrication of thin-film
electrodes for different applications.
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