Abstract
It is a great challenge to fabricate electrode with simultaneous high activity for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Herein, a high‐performance bifunctional electrode formed by vertically depositing a porous nanoplate array on the surface of nickel foam is provided, where the nanoplate is made up by the interconnection of trinary Ni–Fe–Mo suboxides and Ni nanoparticles. The amorphous Ni–Fe–Mo suboxide and its in situ transformed amorphous Ni–Fe–Mo (oxy)hydroxide acts as the main active species for HER and OER, respectively. The conductive network built by Ni nanoparticles provides rapid electron transfer to active sites. Moreover, the hydrophilic and aerophobic electrode surface together with the hierarchical pore structure facilitate mass transfer. The corresponding water electrolyzer demonstrates low cell voltage (1.50 V @ 10 mA cm−2 and 1.63 V @ 100 mA cm−2) with high durability at 500 mA cm−2 for at least 100 h in 1 m KOH.
Highlights
It is a great challenge to fabricate electrode with simultaneous high activity and oxygen evolution reaction (OER) is of great importance for the large-scale for the hydrogen evolution reaction (HER) and the oxygen evolution reaction production of hydrogen from water (OER)
Ni–Fe layered double hydroxide (LDH) nanosheet array is first grown on nickel foam (NF) with 3D open framework and high conductivity (Figure 1a; Figures S1 and S2, Supporting Information).[12]
After the hydrothermal treatment in a solution containing (NH4)6Mo7O24, a solid molybdate containing Ni2+ cation and Fe2+ cation is deposited on the surface of Ni–Fe LDH, which is the precursor of the final product and is named NiFeMo/ NF-Pre
Summary
The electrode is prepared via a three-step strategy (Scheme 1). Ni–Fe layered double hydroxide (LDH) nanosheet array is first grown on NF with 3D open framework and high conductivity (Figure 1a; Figures S1 and S2, Supporting Information).[12]. The O K-edge XANES spectrum of the electrode after oxygen evolution shows a line shape quite similar to Ni–Fe LDH/NF (Figure S46, Supporting Information), and the Raman spectrum presents a distinct peak at ≈550 cm−1 (Figure S43, Supporting Information), which can be ascribed to Ni-based (oxy)hydroxide.[4] It has been reported that metal oxides usually transformed to (oxy) hydroxide during OER owing to the high electrode potential and oxidizing environment,[29] and the positive shift of Mo and Fe K-edge XANES spectra confirms the valence increase of elements in the electrode (Figure S46, Supporting Information). The Ni/NiFeMoOx/NF electrolyzer works well powered by a commercial battery (≈1.5 V) or a solar cell in the open air (Figure S52 and Videos S1 and S2, Supporting Information), indicating a potential application of hydrogen producing in the future
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