Tailoring LaBO3 (B = Mn, Fe, Co, Ni) perovskite oxides for methanol-tolerant oxygen reduction reaction electrocatalysts

Abstract

The crossover of methanol from the anode to the cathode presents a significant challenge, adversely affecting the efficacy of direct methanol fuel cells (DMFCs) by poisoning the cathode catalyst. Here, LaBO₃ (B = Mn, Fe, Co, and Ni) perovskite oxides synthesized by the sol–gel method, followed by calcination, are shown to represent a compelling solution to this challenge by effectively reducing the methanol crossover effect and concurrently improving the sluggish cathodic oxygen reduction reaction (ORR). X-ray diffraction, FTIR, and XPS analyses reveal the establishment of phase-pure LaMnO₃, LaFeO₃, LaCoO₃, and LaNiO₃, perovskite oxides. Further characterization showed that LaMnO₃ possesses the smallest particle size, the highest pore volume, and the largest specific surface area. These factors account for its highest ORR catalytic activity (742 ± 1 mV vs. RHE at −0.1 mA cm⁻², derived from LSV analysis at 1600 rpm) among the synthesized perovskite oxides, which is also comparable to Pt/C (821 ± 2 mV vs. RHE at −0.1 mA cm⁻²). Methanol tolerance studies revealed that the ORR catalytic activities of LaMnO₃, LaFeO₃, LaCoO₃, and LaNiO₃ are negatively shifted by only 3.0 ± 2.0 mV, 3.3 ± 1.5 mV, 10.0 ± 5.0 mV, and 3.0 ± 1.7 mV in the presence of methanol, respectively. This study suggests that the synthesized materials could be promising methanol-tolerant ORR electrocatalysts for improving the performance of DMFCs.