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

Abstract

AbstractIn 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.