Nanotubular Iridium–Cobalt Mixed Oxide Crystalline Architectures Inherited from Cobalt Oxide for Highly Efficient Oxygen Evolution Reaction Catalysis

Abstract

Here, we report the unique transformation of one-dimensional tubular mixed oxide nanocomposites of iridium (Ir) and cobalt (Co) denoted as IrCoO, where x is the relative Ir atomic content to the overall metal content. The formation of a variety of IrCoO (0 ≤ x ≤ 1) crystalline tubular nanocomposites was readily achieved by electrospinning and subsequent calcination process. Structural characterization clearly confirmed that IrCoO polycrystalline nanocomposites had a tubular morphology consisting of Ir/IrO and CoO, where Ir, Co, and O were homogeneously distributed throughout the entire nanostructures. The facile formation of IrCoO nanotubes was mainly ascribed to the inclination of CoO to form the nanotubes during the calcination process, which could play a critical role in providing a template of tubular structure and facilitating the formation of IrO by being incorporated with Ir precursors. Furthermore, the electroactivity of obtained IrCoO nanotubes was characterized for oxygen evolution reaction (OER) with rotating disk electrode voltammetry in 1 M NaOH aqueous solution. Among diverse IrCoO, IrCoO nanotubes showed the best OER activity (the least-positive onset potential, greatest current density, and low Tafel slope), which was even better than that of commercial Ir/C. The IrCoO nanotubes also exhibited a high stability in alkaline electrolyte. Expensive Ir mixed with cheap Co at an optimum ratio showed a greater OER catalytic activity than pure Ir oxide, one of the most efficient OER catalysts.

Electrospun Carbon Nanofibers Encapsulated with NiCoP: A Multifunctional Electrode for Supercapattery and Oxygen Reduction, Oxygen Evolution, and Hydrogen Evolution Reactions

“…To evaluate the HER catalytic activity of the NiCoP electrodes, the LSV curves on the negative potential ranging from 0 to −0.6 V (vs RHE) were obtained as shown in Figure d. The onset of hydrogen evolution was seen emerging at a low potential of −0.10 V (vs RHE) at a scan rate of 5 mV s −1 and a much less overpotential of 130 mV was required to drive a current density of 10 mA cm −2 for NiCoP/CNF900, which is comparatively lower than the reported Ni‐ and Co‐based HER electrodes listed in Table . Inset of Figure e illustrates the required HER overpotential to achieve a current density of 10 mA cm −2 for the prepared electrocatalysts.…”

“…The onset of hydrogen evolution was seen emerging at a low potential of −0.10 V (vs RHE) at a scan rate of 5 mV s −1 and a much less overpotential of 130 mV was required to drive a current density of 10 mA cm −2 for NiCoP/CNF900, which is comparatively lower than the reported Ni-and Co-based HER electrodes listed in Table 3. [12,13,23,29,30,[67][68][69][70][71] Inset of Figure 9e illustrates the required HER overpotential to achieve a current density of 10 mA cm −2 for the prepared electrocatalysts. Since long-term stability is a decisive criterion to evaluate the performance of the electrocatalyst, the CA analysis is studied for a constant potential of −0.28 V (vs RHE) for 20 h as shown in Figure 9e.…”

Atomic Iridium Incorporated in Cobalt Hydroxide for Efficient Oxygen Evolution Catalysis in Neutral Electrolyte

“…For two half‐reactions in water splitting cells, oxygen evolution reaction (OER) at the anode has been regarded as the main bottleneck due to the sluggish kinetics and large overpotential . With this regard, great efforts have been devoted to developing efficient electrocatalysts to accelerate the OER with reduced overpotential, thus improving the energy conversion efficiencies . Recently, the first‐row transition‐metal‐based catalysts, especially Co, Ni, and Fe‐based materials, have attracted extensive attention and been developed as promising electrocatalysts for OER in alkaline media .…”

Proton Exchange Membrane Water Electrolysis as a Promising Technology for Hydrogen Production and Energy Storage

“…Mixed bimetallic oxides of iridium and a non-noble metal have been used to optimize the anode catalyst for PEM electrolyzer application [65][66][67][68][69][70][71][72][73]. The most apparent benefit of bimetallic oxide is to reduce the iridium loading in the catalyst if the catalyst activity remains comparable or higher compared to pure IrOx.…”

“…More importantly, mixed bimetallic oxides modify the electronic or crystal structures of IrOx, which can significantly enhance the OER activity. The bond forming or breaking during OER is governed by the interaction between the O-2p orbital of intermediates with the d orbitals of surface sites of the transition metals [66][67][68][70][71][72][73]. Thus, the OER activity depends on the dorbital electronic structure of the transitional metals.…”