Highly Durable and Efficient Ni-FeO_x/FeNi₃ Electrocatalysts Synthesized by a Facile In Situ Combustion-Based Method for Overall Water Splitting with Large Current Densities

Abstract

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.

Duplex Interpenetrating-Phase FeNiZn and FeNi3 Heterostructure with Low-Gibbs Free Energy Interface Coupling for Highly Efficient Overall Water Splitting

“…At the current density of 100 and 500 mA cm −2 , its overpotentials are 258 and 315 mV, respectively, which is also much smaller than those of RuO 2 @NiFe (331 and 397 mV) and NiFe foam (372 and 432 mV). Such the OER activity for FeNiZn/FeNi 3 @NiFe-24 h surpasses some similar electrocatalysts reported previously as shown in Table S1 [ 19 , 20 , 24 , 26 , 38 , 39 , 47 – 51 ].

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“…At the current density of 100 and 500 mA cm −2 , the overpotentials of FeNiZn/FeNi 3 @NiFe-24 h sample are only 102 and 177 mV, which are much lower than those of other electrodes. Moreover, the HER activity of FeNiZn/FeNi 3 @NiFe-24 h sample is superior to the comparable electrocatalysts reported previously as shown in Table S2, especially under the high current density [ 19 , 20 , 24 , 26 , 38 , 44 , 48 – 51 , 53 ]. As stated above, it is regarded that the free-standing multimodal porous interpenetrating-phase heterostructure is responsible for the unique HER activity of FeNiZn/FeNi 3 @NiFe-24 h sample in virtue of high density of active sites and fluent mass transfer [ 3 ].…”

“…In this respect, self-supporting electrode is preferable for exposing more active sites and reducing the interface resistance owing to free of conductive binders [ 21 – 23 ]. Recently, the in situ construction of nanostructured electrocatalysts on bulky metal foam has been one powerful strategy to improve the efficacy of overall water splitting [ 24 – 26 ]. For example, Wang et al prepared the IrNi-FeNi 3 hybrid supported on nickel foam (IrNi-FeNi 3 /NF), which displays the ultralow overpotentials of 330.0/288.8 mV to generate a current density 1000 mA cm −2 for OER and HER as well good stability for overall water splitting [ 26 ].…”

Highly Durable Compositionally Variant Bifunctional Tetrametallic Ni–Co–Mn–Fe Phosphide Electrocatalysts Synthesized by a Facile Electrodeposition Method for High-Performance Overall Water Splitting

“…26 The incorporation of Fe into Ni oxide resulted in enhanced electrocatalytic water splitting with high durability in alkaline media over a long period of time. 27,28 Mixed TM oxides exhibited higher activity than their single counter parts, revealing the positive synergy between the components. For example, Ni−Fe hydroxides, 29 layered double hydroxides, 30 alloys, 31,32 and nitrides 33 have extensively been investigated.…”

NiSe and Fe-Based Layerd Double Hydroxide Nanosheet/Ni Foam Bifunctional Catalyst for Water Splitting

“…However, the OER performance of these catalysts is still unsatisfactory due to their poor stability in alkaline electrolytes, which hinder their applications for OWS. On the contrary, transition-metal oxides , and hydroxides, , especially Fe-based layered double hydroxides (LDHs), have been regarded as efficient catalysts for OER under an alkaline environment due to the strong synergistic effect attributed to the incorporation of Fe and tunable electronic, catalytic, and electrochemical properties. These aspectes can effectively promote the absorption and dissociation of hydroxyl species. , For example, Peng et al designed a cation-vacancy-decorated NiFe-LDH catalyst with high efficiency and stability in OER .…”