A Facile Molecular Approach to Amorphous Nickel Pnictides and Their Reconstruction to Crystalline Potassium-Intercalated γ-NiOOHx Enabling High-Performance Electrocatalytic Water Oxidation and Selective Oxidation of 5-Hydroxymethylfurfural.

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The low-temperature molecular precursor approach can be beneficial to conventional solid-state methods, which require high temperatures and lead to relatively large crystalline particles. Herein, a novel, single-step, room-temperature preparation of amorphous nickel pnictide(NiE; EP, As) nanomaterials is reported, starting from NaOCE(dioxane)n and NiBr2 (thf)1.5 . During application for the oxygen evolution reaction (OER), the pnictide anions leach, and both materials fully reconstruct into nickel(III/IV) oxide phases (similar to γ-NiOOH) comprising edge-sharing (NiO6 ) layers with intercalated potassium ions and a d-spacing of 7.27Å. Remarkably, the intercalated γ-NiOOHx phases are nanocrystalline, unlike the amorphous nickel pnictide precatalysts. This unconventionalreconstruction is fast and complete, whichisascribed to the amorphous nature of the nanostructured NiE precatalysts. The obtained γ-NiOOHx can effectively catalyse the OERfor 100 h at a high current density (400 mAcm-2 ) and achieves outstandingly high current densities (>600 mAcm-2 ) for the selective, value-added oxidation of 5-hydroxymethylfurfural (HMF). The NiP-derived γ-NiOOHx shows a higher activity for both processes due to more available active sites.It is anticipated that the herein developed, effective, room-temperature molecular synthesis of amorphous nickel pnictide nanomaterials can be applied to other functional transition-metal pnictides.