In-situ generated Co2P nanoparticle-embedded porous carbon membrane as an advanced hybrid electrode for high-areal-capacitance supercapacitors

Hybridizing powdery carbons with transition metal phosphides (TMPs) can effectively address the issues of sluggish kinetics and volume expansion associated with TMPs in supercapacitors (SCs). However, the practical use of powdery TMPs/carbon materials in SCs is limited by tedious electrode preparation process, unfavorable performance, and inferior cycling stability. Herein, we develop carbon membrane-based hybrid electrodes (Co2P@CTF) by the direct carbonization of Co-containing tofu (TF) aerogel prepared by coagulating soybean proteins using Co2+ ions. During carbonization, the cross-linked protein frameworks were transformed into a porous, mechanically strong, and conductive carbon matrix, whereas the Co species were in situ self-phosphorized to be highly dispersed carbon-coated Co2P nanoparticles without using external phosphorus sources. The best Co2P@CTF electrode (Co2P@CTF-1000) demonstrates a high areal capacitance (Ca) of 2.44 F cm−2 at 1.0 mA cm−2. Moreover, a symmetric SC assembled with Co2P@CTF-1000 deliveries a Ca of 1.33 F cm−2 at 1.0 mA cm−2, achieves an energy density of 90 μWh cm−2 at a power density of 699.4 μW cm−2, and retains a 104.8% capacitance with a nearly unit coulomb efficiency at 10 mA cm−2 after 50000 cycles. This study offers an effective strategy towards carbon membrane-supported TMPs hybrid electrodes based on the direct self-phosphorization mechanism for the practical applications in SCs.