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

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.