Covalent Porphyrin Framework-Derived Fe₂P@Fe₄N-Coupled Nanoparticles Embedded in N-Doped Carbons as Efficient Trifunctional Electrocatalysts

Abstract

A new porous covalent porphyrin framework (CPF) filled with triphenylphosphine was designed and synthesized using the rigid tetrakis(p-bromophenyl)porphyrin (TBPP) and 1,3,5-benzenetriboronic acid trivalent alcohol ester as building blocks. The carbonization of this special CPF has afforded coupled Fe₂P and Fe₄N nanoparticles embedded in N-doped carbons (Fe₂P/Fe₄N@N-doped carbons). This CPF serves as an "all in one" precursor of Fe, N, P, and C. The porous property and solid skeleton of the CPF endow Fe₂P/Fe₄N@N-doped carbons with porous structure and a high degree of graphitization. As a result, Fe₂P/Fe₄N@N-doped carbons exhibited highly efficient multifunctional electrocatalytic performance for water splitting and oxygen electroreduction. Typically, Fe₂P/Fe₄N@C-800, obtained at a heat-treatment temperature of 800 °C, showed an ORR half-wave potential of 0.80 V in alkaline media and 0.68 V in acidic media, close to that of commercial Pt/C catalysts. Fe₂P/Fe₄N@C-800 also displayed efficient OER and HER activities, comparable to other phosphide and nitride electrocatalysts. The coupled Fe₄N and Fe₂P nanoparticles embedded in carbons exert unique catalytic efficiency for water splitting and fuel cells.