In Situ Synthesis Strategy for Hierarchically Porous Ni₂P Polyhedrons from MOFs Templates with Enhanced Electrochemical Properties for Hydrogen Evolution

Abstract

The development of highly active and stable noble metal-free electrocatalysts of hydrogen evolution reaction (HER) under both acidic and basic conditions for renewable-energy conversion techniques is of great significance. Herein, a practical in situ synthesis strategy for a three-dimensional NiP polyhedron with a hierarchically porous structure was presented, which was efficiently obtained from a nickel centered metal-organic frameworks (MOF-74-Ni) by direct low-temperature phosphorization. The as-prepared NiP polyhedron showed a high BET surface area (175.0 m·g), hierarchically porous property, and outstanding metal dispersion, which well inherited the morphology and porosity of its MOF precursor. Compared with NiP particles obtained from a nonporous precursor, the as-prepared NiP polyhedron used as electrocatalyst exhibited excellent electrocatalytic performance toward the HER, with a low overpotential of 158 mV to produce the cathodic current density of 10 mA cm. A small Tafel slope of 73 mV per decade is obtained for NiP polyhedron, which revealed a Volmer-Heyrovsky mechanism during the HER. In addition, benefiting from the structural stability, the porous NiP polyhedron used as a electrocatalyst showed satisfactory long-term durability for the HER in acidic media.

Controlled Pyrolysis of Ni‐MOF‐74 as a Promising Precursor for the Creation of Highly Active Ni Nanocatalysts in Size‐Selective Hydrogenation

“…Ni-MOF-74 before heat treatment showed two distinctp eaks at around 857.8 eV and 862.4 eV,i ndicating that Ni speciesi nN i-MOF-74 existeda s Ni 2 + ions in the Ni cluster. [52][53] No noticeable change was observedi nt he spectrao fN i-MOF-74-250 and Ni-MOF-74-300. The structuralt ransformationw as confirmed in Ni-MOF-74-400, in which the new peaks derived from Ni metal species appeared, and their intensities increasedw ith increasing heat treatment temperature.H owever,t hese results for Ni-MOF74-300 do not correspond with the results of XRD,T PD andX AFS in terms of the absence of Ni metal species.…”

“…From this result, Ni species in Ni/AC‐300 existed in the NiO state, which supports the XRD results. Ni‐MOF‐74 before heat treatment showed two distinct peaks at around 857.8 eV and 862.4 eV, indicating that Ni species in Ni‐MOF‐74 existed as Ni 2+ ions in the Ni cluster . No noticeable change was observed in the spectra of Ni‐MOF‐74‐250 and Ni‐MOF‐74‐300.…”

Assembling Ultrasmall Copper‐Doped Ruthenium Oxide Nanocrystals into Hollow Porous Polyhedra: Highly Robust Electrocatalysts for Oxygen Evolution in Acidic Media

“…Clearly, it indicates the faster electrocatalytic kinetics for S‐300. [2c,27] To gain insight for the intrinsic activity, the turnover frequency (TOF) of these electrocatalysts was calculated based on a previously reported method and is shown in Table S4 (Supporting Information) . Assuming that the Ru ions are all active, the S‐300 electrocatalyst exhibits a high TOF of 0.0528 s −1 , which is 17 times larger than that of the commercial RuO 2 catalyst (0.0031 s −1 ) at an overpotential of 250 mV.…”

Metal–Organic Framework Based Catalysts for Hydrogen Evolution

“…MIL-101-NH 2 , [88] MIL-53, [89] MOF-100, [90] MOF-199, [91] MOF-74, [92] Ni-BTC, [87,93,94] and other Ni-, [95][96][97] Co-, [98][99][100][101] Mo-, [97] Al-based [102,103] monometallic and bimetallic MOFs are reported as precursors for the synthesis of various catalysts with specifically designed chemical components and structures. MIL-101-NH 2 , [88] MIL-53, [89] MOF-100, [90] MOF-199, [91] MOF-74, [92] Ni-BTC, [87,93,94] and other Ni-, [95][96][97] Co-, [98][99][100][101] Mo-, [97] Al-based [102,103] monometallic and bimetallic MOFs are reported as precursors for the synthesis of various catalysts with specifically designed chemical components and structures.…”