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

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.