Porous Nitrogen Self‐Doped Carbon Wrapped Iron Phosphide Hollow Spheres as Efficient Bifunctional Electrocatalysts for Water Splitting

Abstract

In this work, a series of hybrid materials of N‐self‐doped carbon wrapped Fe2P/FeP hollow spheres were prepared by using a two‐step thermal conversion of precursors derived from the in situ coating of polyaniline on commercial Prussian blue. The precursors were pyrolyzed in N2 to form the N‐doped carbon coating on carbon‐iron materials; this was followed by subsequent phosphorization using NaH2PO2 as a phosphorus source, yielding the hybrid materials of N‐doped carbon wrapped Fe2P/FeP hollow spheres. The resulting hybrid materials showed high Brunauer‐Emmett‐Teller surface areas, pore volumes, and nitrogen contents, which were, more than 80 % pyridinic‐N. The hybrid materials were evaluated as electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH, and they have exhibited excellent electrocatalytic activities in the two reactions. In the case of the optimum sample, the 0.75‐NC−FexP catalyst, a low overpotential/Tafel slope of 193 mV/58 mV ⋅ dec−1 for HER and 302 mV/42 mV ⋅ dec−1 for OER were obtained. More importantly, the catalyst showed high catalytic activity for overall water splitting and only 1.63 V of cell voltage was needed to reach 10 mA/cm2 in a two‐electrode electrolyzer. The catalyst also exhibited robust long‐term durability and only a 16.0 % decrease in current density was observed after a 10 h chronoamperometric testing at 1.63 V. The results suggest that the sample is a promising alternative non‐precious‐metal catalyst for overall water splitting.

CoP/N-Doped Carbon Hollow Spheres Anchored on Electrospinning Core–Shell N-Doped Carbon Nanofibers as Efficient Electrocatalysts for Water Splitting

“…In this respect, a hollow structure with abundant hierarchical pores would be expected to provide a highly effective surface area, 33 highly exposed catalytic active sites, 34 and high porosity to improve mass transport and thus enhance catalytic activity of the catalyst. 35 The core−shell nanostructures with good stability, functionality, and dispersibility can also efficiently enhance the electrocatalytic performance of a catalyst. 36 Especially, more effective active sites and a large decrease in charge transport resistance can be achieved from the employment of the electrospinning core−shell nanofiber.…”

“…Besides composition, the structure is also vitally important for improving the catalytic activity of a catalyst. In this respect, a hollow structure with abundant hierarchical pores would be expected to provide a highly effective surface area, highly exposed catalytic active sites, and high porosity to improve mass transport and thus enhance catalytic activity of the catalyst . The core–shell nanostructures with good stability, functionality, and dispersibility can also efficiently enhance the electrocatalytic performance of a catalyst .…”

Anchoring of Ni12P5 Microbricks in Nitrogen- and Phosphorus-Enriched Carbon Frameworks: Engineering Bifunctional Active Sites for Efficient Water-Splitting Systems

“…The long-term operation of Ni 12 P 5 @N,P-C­(5) in a water electrolyzer was tested at 0.3 V vs RHE, which showed its stable and effective water-splitting activity for 10 h (Figure f). The comparative performance of the prepared Ni 12 P 5 microstructures with those of other phosphide-based electrolyzers is shown in Figure g. − ,− …”

Recent Advances in 1D Electrospun Nanocatalysts for Electrochemical Water Splitting

“…In this regard, a hollow structure with a large number of layered pores will provide efficient surface area, highly exposed catalytic active sites, and high porosity to improve mass transfer. [ 141–144 ] In view of the aforementioned considerations, Tong et al [ 141 ] conveniently prepared a series of CoP/N‐doped carbon hollow sphere hybrids anchored on core–shell NCNFs by electrospinning technology. According to the TEM ( Figure a,b), it can be seen that small spheres with a diameter of about 30–50 nm are uniformly dispersed on the fibers with an average diameter of 300 nm, and the fibers have a core–shell structure.…”