FeCoNi Ternary Spinel Oxides Nanosheets as High Performance Water Oxidation Electrocatalyst

Abstract

FeCoNi spinel oxides nanosheets array directly supported on the Ni foam substrate were prepared via a facile wet chemical method with 2-methylimidazole as a structure directing agent and subsequently annealing. The as-prepared 0.1FeÀ CoNiO/NF offers high intrinsic catalytic activity, high surface area and good conductivity, resulting in enhanced activity for the oxygen evolution reaction (OER) in the alkaline solution. It demonstrates an ultralow overpotentials of 240 mV at 10 mA cm À 2 and a small Tafel slope of 36.8 mV dec À 1 , with attractive durability during long-term operation in 1 M KOH solution.Hydrogen is one of clean energy with irreplaceable advantages over energy sources such as wind and nuclear power. [1] Natural gas reforming is the main approach to produce hydrogen. However, natural gas reforming needs external energy input and release CO 2 as by-product, [2] never mind that the produced H 2 from this cost more energy for the further purifications process. In contrast, Photo/electrocatalytic water splitting has the advantage of effectively producing high purity hydrogen, but it is also suffering from many drawbacks such as high overpotential and low efficiency. [3] Oxygen evolution reaction (OER) with a four-electron transfer process is a half reaction for overall water splitting, which is more complicated and kinetically sluggish. [4] So far, noble metal like iridium (Ir), ruthenium (Ru) and their compounds were realized as efficient water oxidation catalysts. [5] However, the scarce and high cost of these materials limit their large-scale commercial applications. Thus it is urgent to prepare high-performance OER catalysts based on less noble elements.Among various low-cost OER catalysts, one promising candidate is spinel-structured oxides, due to its outstanding electrocatalysis performance and corrosion resistance in alkaline environment. [6] Typically, Co 3 O 4 has triggered considerable interest due to its earth abundance and easy to prepare. However, limited by low catalytic activity and poor electrical conductivity, Co 3 O 4 still presents high OER overpotentials. [7] In this regard, a number of strategies have been developed to solve these issues. Highly conductive substrates (such as graphite, single-walled carbon nanotubes and metal foam) are employed to improve the conductivity and increase the number of active sites of the catalyst. [8] Another option is to improve water oxidation through the modulation of electronic structures by doping. [9] It has been found that Ni has good interaction strength with OH ads , satisfying the Sabatier principle for catalyst design. [10] As a result, NiCo-based spinel oxides has gained considerable interest due to its excellent electrochemical activity. [11] Further, Fe-doping has been demonstrated as an effectively approach to improve the charge transport between the catalyst and the electrolytes. [12] On the hand, microstructure control has been employed to optimize the catalysis performance. [9] For instance, Co 3 O 4 crystals with different morpholo...

Nanosized high entropy spinel oxide (FeCoNiCrMn)3O4 as a highly active and ultra-stable electrocatalyst for the oxygen evolution reaction

“…For example, Arriaga et al 20 synthesized spinel NiCo 2 O 4 nanoparticles, which exhibit superior catalytic activity compared to Co 3 O 4 , and the addition of the Ni element greatly increased the number of surface-active sites and improved the conductivity. Furthermore, Sun et al 21 synthesized 0.1-FeCoNiO/NF by doping 0.1 mM Fe in CoNiO, which shows higher OER performance than that of CoNiO/NF, Co 3 O 4 and NiO since Fe can promote charge transport between the catalyst and the electrolytes. In addition, bimetallic oxides MnCo 2 O 4 (ref.…”

Effect of Iron Concentration and Annealing Conditions on the Catalytic Performance of Co–Mn Spinel Oxides with a Unique Nanowire–Nanosheet Coexisting Structure for Water Oxidation

“…It can be ascribed to the unique nanowire−nanosheet coexistence structure supported by porous Ni foam and Fe incorporation, and they have optimum bond energetics for the adsorption of OER intermediates, 38 which is beneficial for rapid desorption of gas, resulting in negligible destruction of nanostructure and change in the chemical composition and states of the sample. 8 It is worthy to note that morphological structure is critical for the exposure of active centers and the surface adsorption ability of the reactants. 39 As shown in Figures 2c−f and S3b−d, the increased Fe incorporation leads to a visible change of morphology, especially the increased nanosheet amount.…”

“…Furthermore, XPS of CoMnFeO 4 tested for a long period showed virtually the same spectra as the original one (Figure S12). It can be ascribed to the unique nanowire–nanosheet coexistence structure supported by porous Ni foam and Fe incorporation, and they have optimum bond energetics for the adsorption of OER intermediates, which is beneficial for rapid desorption of gas, resulting in negligible destruction of nanostructure and change in the chemical composition and states of the sample . It is worthy to note that morphological structure is critical for the exposure of active centers and the surface adsorption ability of the reactants .…”

“…Therefore, high-activity, earth-abundant, inexpensive, non-noble elements-based electrocatalysts are seen as potential candidates for water oxidation research. Until now, some success has been achieved with the use of non-precious metal-based catalysts for water oxidation. − This includes spinel transition metal-based oxides (TMO, such as NiMn 2 O 4 , FeCo 2 O 4 , CoMn 2 O 4 , and Co 2 MnO 4 ). For instance, Menezes and co-workers synthesized NiMn 2 O 4 with predesign ratios of Ni/Mn to boost the efficiency of OER .…”