Fabrication of a mesoporous Ba0.5Sr0.5Co0.8Fe0.2O3-delta perovskite as a low-cost and efficient catalyst for oxygen reduction

摘要

A precious metal-free cathode catalyst, mesoporous Ba0.5Sr0.5Co0.8Fe0.2O3-delta (m-BSCF), with a well crystallized perovskite framework and a porous structure (pore size of similar to 10 nm) has been synthesized by a one-step co-nanocasting method. The obtained mesoporous perovskite m-BSCF demonstrated a much higher oxygen reduction reaction catalytic activity than its macroporous (CS-BSCF of similar to 5 mu m pore size) and nonporous counterparts (SG-BSCF). The mesoporous structure and oxygen vacancies (V-o) endowed the obtained perovskite oxide m-BSCF with an approximate 4e(-) pathway for the ORR comparable to the benchmark 20 wt% Pt/C and a stable electro-catalytic activity with 91% current density being retained after 5000 cycles, and excellent methanol tolerance. The redox couples Co4+/Co3+ and Fe3+/Fe2+ are proposed to accelerate the ORR on active species, i. e., MOOH (M = Co, Fe) groups produced by the substitution species of Co and Fe in the B-site of perovskite m-BSCF, and in the meantime oxygen vacancies (V-o) generated by the redox couples play a key role in activating the oxygen molecules.