Suppression of CH4 formation via Mn and Fe partial substitution in LaCoO3 for the preferential oxidation of CO in H2 streams

The selective removal of CO from hydrogen-rich reformate streams via preferential oxidation (CO-PROX) remains a critical challenge for the deployment of low temperature fuel cells, as CO poisons Pt anode catalysts. This work reports a B-site engineering strategy in which Co is partially substituted with Mn or Fe in LaCoO 3 perovskites to enhance oxygen mobility and redox performance while suppressing side reactions. LaCo 1-x M x O 3 (M = Mn or Fe; x = 0-0.2) catalysts are synthesized by the Pechini method and characterized using XRD, STEM-EDS, TPR/TPO, and in-situ XRD. Mn and Fe substitution expands the perovskite lattice and shifts Co 3+ /Co 2+ redox transitions to lower temperatures. The first reduction peak decreases from 480°C for LaCoO 3 to 379°C and 430°C for Mn- and Fe-substituted catalysts, respectively. LaCo 0.85 Mn 0.15 O 3 achieves 99.9% CO conversion at 250°C, while LaCo 0.85 Fe 0.15 O 3 maintains ∼90% conversion at 310°C, both with negligible CH 4 formation. Long-term tests confirm stable operation.