High-performance electrocatalysts with superior stability are critically important for their practical applications in hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). Herein, we report a facile method to fabricate urchin-like CoP nanocrystals (NCs) as catalyst for both HER and ORR with desirable electrocatalytic activities and long-term stability. The urchin-like CoP NCs with a diameter of 5 μm were successfully prepared by a hydrothermal reaction following a phosphidation treatment in N2 atmosphere and present excellent HER catalytic performance with a low onset overpotential of 50 mV, a small Tafel slope of 46 mV/decade, and an exceptional low overpotential of ~180 mV at a current density of 100 mA cm(-2) with a mass loading density of 0.28 mg/cm(2). Meanwhile, a remarkable ORR catalytic activity was observed with a half-potential of 0.7 V and an onset potential of 0.8 V at 1600 rpm and a scan rate of 5 mV s(-1). More importantly, the urchin-like CoP NCs present superior stability and keep their catalytic activity for at least 10 000 CV cycles for HER in 0.5 M H2SO4 and over 30 000 s for ORR in 0.1 M KOH, which is ascribed to their robust three-dimensional structure. This urchin-like CoP NCs might be a promising replacement to the Pt-based electrocatalysts in water splitting and fuel cells.
Tuning the crystal phase of metal alloy nanomaterials has been proved as ignificant way to alter their catalytic properties based on crystal structure and electronic property. Herein, we successfully developed as imple strategy to controllably synthesize ar are crystal structure of hexagonal close-packed (hcp) NiFen anoparticle (NP) encapsulated in aN -doped carbon (NC) shell (hcp-NiFe@NC). Then, we systemically investigated the oxygen evolution reaction (OER) performance of the samples under alkaline conditions,i n which the hcp-NiFe@NC exhibits superior OER activity compared to the conventional face-centered cubic (fcc) NiFe encapsulated in aN-doped carbon shell (fcc-NiFe@NC). At the current densities of 10 and 100 mA cm À2 ,t he hcp-NiFe@NC with Fe/Ni ratio of % 5.4 %only needs ultralow overpotentials of 226 mV and 263 mV versus reversible hydrogen electrode in 1.0 m KOHe lectrolyte,r espectively,w hich were extremely lower than those of fcc-NiFe@NC and most of other reported NiFe-based electrocatalysts.W ep roposed that hcp-NiFep ossesses favorable electronic property to expedite the reaction on the NC surface,r esulting higher catalytic activity for OER. This researchp rovides an ew insight to design more efficient electrocatalysts by considering the crystal phase correlated electronic property.
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