Size-Controlled Synthesis and Microstructure Investigation of Co₃O₄ Nanoparticles for Low-Temperature CO Oxidation

Noble-metal-free functional oxides are active catalysts for CO oxidation at low temperatures. Spinel-type cobalt oxide (Co₃O₄) nanoparticles can be easily synthesized by impregnation of activated carbon with concentrated cobalt nitrate and successive carbon burn off. Mean size and particle size distribution can be tuned by adding small amounts of silica to the carbon precursor, as witnessed by whole powder pattern modeling of the X-ray powder diffraction data. The catalytic tests performed after silica removal show a significant influence of the mean domain size and of size distribution on the CO oxidation activity of the individual Co₃O₄ specimens, whereas defects play a less important role in the present case

Design of N‑Coordinated Dual-Metal Sites: A Stable and Active Pt-Free Catalyst for Acidic Oxygen Reduction Reaction

We develop a host-guest strategy to construct an electrocatalyst with Fe-Co dual sites embedded on N-doped porous carbon and demonstrate its activity for oxygen reduction reaction in acidic electrolyte. Our catalyst exhibits superior oxygen reduction reaction performance, with comparable onset potential (<i>E</i>_onset, 1.06 vs 1.03 V) and half-wave potential (<i>E</i>_1/2, 0.863 vs 0.858 V) than commercial Pt/C. The fuel cell test reveals (Fe,Co)/N-C outperforms most reported Pt-free catalysts in H₂/O₂ and H₂/air. In addition, this cathode catalyst with dual metal sites is stable in a long-term operation with 50 000 cycles for electrode measurement and 100 h for H₂/air single cell operation. Density functional theory calculations reveal the dual sites is favored for activation of O-O, crucial for four-electron oxygen reduction