Collaborative integration of ultrafine Fe2P nanocrystals into Fe, N, P-codoped carbon nanoshells for highly-efficient oxygen reduction

Abstract

The rational design and facile synthesis of cost-effective and high-performance carbon-based catalysts for oxygen reduction reaction (ORR) is of great significance but remain challenging. Herein, we report the crafting of a robust Fe,N,P-codoped, ultrafine Fe2P nanocrystals decorated, highly hierarchical porous carbon nanoshells (denoted Fe,N,P-CNSs/Fe2P) via a simple yet robust one-step synergetic phosphorization and pyrolysis approach for highly-efficient ORR. Specifically, well-defined polypyrrole-co-polyaniline hollow nanospheres with a shell thickness of ≈ 43 nm (PPy-co-PANI-HNs) are first elaborately synthesized via a facile soft-templating (Triton X-100 micelles) copolymerization of pyrrole and aniline monomers. Subsequent one-step synergetic phosphorization and pyrolysis of PPy-co-PANI-HNs pre-impregnated with NaH2PO2·H2O and FeCl3 (H2PO2-,Fe3+@PPy-co-PANI-HNs) yields Fe,N,P-CNSs/Fe2P with a well-crafted ultrathin nanoshell (shell thickness of ≈13 nm) architecture containing abundant hierarchical porosity. Remarkably, an alkaline electrolyte capitalizing on the resulting Fe,N,P-CNSs/Fe2P manifests excellent ORR performance with the half-wave and onset potentials (E1/2 of 0.854 V and Eonset of 0.955 V) comparable to Pt/C, diffusion limited current density (JL of −5.98 mA cm−2) higher than Pt/C, and long-time durability and methanol resistance better than Pt/C, demonstrating great potential as air cathode in zinc-air batteries (maximum power density of 170 mW cm−2 and specific capacity of 824.5 mA h g−1). Combined experimental and theoretical studies reveal that the impressive ORR performance of Fe,N,P-CNSs/Fe2P originates from simultaneous compositional (i.e., Fe,N,P-codoping and ultrafine Fe2P nanocrystals decorating) and structural (i.e., hierarchically porous ultrathin nanoshell architecture) tailoring enabled by the judicious one-step synergetic phosphorization and pyrolysis.