An iron and lanthanide heterobimetallic coordination polymer derived electrocatalyst showing enhanced activity and stability for the oxygen reduction reaction

Abstract

It is desirable to develop noble-metal-free electrocatalysts with both excellent activity and stability for the oxygen reduction reaction (ORR) in clean energy conversion devices. Herein, we report an Fe, La co-doped FeLaNC electrocatalyst obtained by pyrolyzing a heterobimetallic coordination polymer [La₂L₃(CH₃OH)₄]_∞ loaded on carbonized ZIF-8, which was synthesized from 1,1′-ferrocenedicarboxylic acid (H₂L₁) and lanthanum salt. The FeLaNC catalyst exhibited higher ORR activity with a half-wave potential (E_1/2) of 0.874 V (vs. RHE) than the control catalyst FeNC (E_1/2 = 0.864 V) without the La dopant as well as commercial 20 wt% Pt/C (E_1/2 = 0.862 V) in 0.1 M KOH solution, and FeLaNC displayed excellent stability with negligible half-wave potential decay after 10 000 potential cycles. When FeLaNC was applied as a cathodic electrocatalyst in Zn–air batteries (ZABs), the open circuit voltage (OCV) and maximum power density (P_max) of the FeLaNC-based ZABs reached 1.46 V and 130 mW cm⁻², respectively, which were significantly higher than those of Pt/C (OCV = 1.41 V and P_max = 120 mW cm⁻²). The introduction of La³⁺ into Fe–N–C catalysts not only promoted ORR activity by regulating the electron density of Fe–N_x sites but also enhanced the stability by eliminating the harmful radicals, which provided an effective approach to prepare high-performance and stable electrocatalysts to be applied in energy conversion devices.