A facile approach to construct Co2P@Fe(PO3)2-NCNT heterojunction with highly dispersed active sites for photosensitive oxygen reduction reaction and oxygen evolution reaction

A facile pre -anchored approach is employed to prepare a non -precious bifunctional electrocatalyst Co2P@Fe (PO3)2-NCNT with a p -n heterojunction structure for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Firstly, a well -designed Co3O4/Fe(CN)64- @PPy-CNT precursor is synthesized via an one -pot method, in which Fe(CN)64- and Co3O4 are pre -anchored on polypyrrole (PPy) chains that in -situ formed on carbon nanotubes (CNTs). Subsequent pyrolysis and phosphating of the precursor resulted in the Co2P@Fe (PO3)2-NCNT catalyst, which contains highly dispersed Co2P and Fe(PO3)2 nanoparticles within N -doped carbon (NCNT). Compared to Co2P-NCNT with only n -type Co2P, introducing p -type Fe(PO3)2 into Co2P@Fe(PO3)2- NCNT leads to not only its Fermi level (EF) closer to Pt, but a larger energy gap between EF and the conduction band. This makes it a higher half -wave potential (E1/2) of 0.85 V for ORR, and a lower overpotential (eta 10) of only 300 mV for OER, superior to both Co2P-NCNT (E1/2 = 0.76 V,eta 10 = 510 mV), the commercial 20% Pt/C (E1/2 = 0.84 V) and RuO2 (eta 10 = 360 mV). Impressively, the unique p -n heterojunction structure of Co2P@Fe(PO3)2- NCNT is resulted in the significant improvement on both ORR with E1/2 increased by 10 mV and OER with overpotential decreased by 20 mV under visible light.