Porous carbon membrane embedded with high-loading NiCoP nanoparticles as bifunctional electrodes for supercapacitors and electrocatalytic water splitting.

Porous carbon membrane-based bifunctional electrodes (NiCoP@CSA) are developed direct carbonization, followed by vapor-phase phosphidation of Ni/Co-crosslinked starch aerogel. During the carbonization and phosphidation processes, the crosslinked starch framework is transformed into a hierarchically porous, conductive, and mechanically strong carbon membrane, while the Ni/Co species are concurrently converted into embedded carbon-coated NiCoP nanoparticles with a loading exceeding 40 wt%. Benefitting from its hierarchically porous structure, excellent electrolyte wettability, and abundant active sites, the best NiCoP@CSA electrode exhibits a high areal specific capacitance () of 9.41 F cm at 2 mA cm, a volumetric capacitance () of 115.0 F cm at 20 mA cm, and an NiCoP loading-based mass capacitance () of 1108.9 F g at 0.2 A g in a three-electrode system. In addition, an asymmetrical supercapacitor (SC) assembled by pairing NiCoP@CSA and an activated carbon/Ni foam (AC/NF) exhibits a high of 2.46 F cm at 2 mA cm, an energy density of 0.41 mWh cm at a power density of 1.1 mW cm, and a capacitance retention of 75% with a unit coulombic efficiency after 10 000 cycles. In addition, NiCoP@CSA can be directly used as a binder-free bifunctional electrode for electrocatalytic water splitting, requiring low overpotentials of 192.4 and 418.5 mV to achieve a current density of 100 mA cm for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, and it exhibits superior durability in the HER (>100 h at 20 mA cm) and OER (>40 h at 20 mA cm).