NiOOH Exfoliation-Free Nickel Octahedra as Highly Active and Durable Electrocatalysts Toward the Oxygen Evolution Reaction in an Alkaline Electrolyte

Abstract

A layered β-NiOOH crystal with undercoordinated facets is an active and economically viable nonnoble catalyst for the oxygen evolution reaction (OER) in alkaline electrolytes. However, it is extremely difficult to enclose the β-NiOOH crystal with undercoordinated facets because of its inevitable crystal transformation to γ-NiOOH, resulting in the exfoliation of the catalytic surfaces. Herein, we demonstrate {111}-faceted Ni octahedra as the parent substrates whose surfaces are easily transformed to catalytically active β-NiOOH during the alkaline OER. Electron microscopic measurements demonstrate that the horizontally stacked β-NiOOH on the surfaces of Ni octahedra has resistance to further oxidation to γ-NiOOH. By contrast, significant crystal transformation and thus the exfoliation of the γ-NiOOH sheets can be observed on the surfaces of Ni cubes and rhombic dodecahedra (RDs). Electrocatalytic measurements show that the β-NiOOH formed on Ni octahedra exhibits highly enhanced OER durability compared to the Ni cubes, Ni RDs, and the state-of-the-art Ir/C catalysts.

Synthesis and water oxidation electrocatalytic and electrochromic behaviours of mesoporous nickel oxide thin film electrodes

“…4 It is likely that the surface of m-NiO is covered with both b-NiOOH and g-NiOOH, which form during the water oxidation process, and a-Ni(OH) 2 and b-Ni(OH) 2 during the reverse scan. 39,40 This may clarify the changes in the CV curves over multiple cycles (see Fig. S4 †).…”

Ultrathin Ni(0)‐Embedded Ni(OH)2 Heterostructured Nanosheets with Enhanced Electrochemical Overall Water Splitting

“…Recently, it has been reported that non‐precious‐metal nanomaterials can be used as the potential alternative catalysts for HER or OER . For example, Ni‐based sulfides and phosphides were synthesized for the electrocatalytic HER, and Ni‐based oxides and hydroxides exhibited electrochemical oxygen evolution activities . Since the overall water splitting is critical in the practical application, it is desired to develop bifunctional electrocatalysts .…”

Recent Progress on Nickel‐Based Oxide/(Oxy)Hydroxide Electrocatalysts for the Oxygen Evolution Reaction

“…Modifications of nickel (oxy)hydroxide catalysts to boost OER performance are mainly focusedo n enhancing the intrinsic activity,e xposing more active sites and promoting charget ransfer by heteroatom doping as well as designing and fabricating highly efficient nanostructures/nanocomposites of the catalysts. [28] Heteroatomic Fe-doping in nickel-based (oxy)hydroxide was demonstrated as one of the most promising methods to improve the OER activity.B oettcher and co-workersf ound that the intentional and/or incidental incorporation of Fe improved the catalytic activityo fn ickel (oxy)hydroxide significantly (Figure 3a and b). They demonstrated that the introductionofF eaffects the NiOOH electronic structure and exerts ap artial-charge transfera ctivation on Ni.…”