High-dispersion Co/N/C ultra-thin carbon nanosheets modified with trace Ce as efficient oxygen reduction reaction catalysts

Abstract

Efficient precious metal-free oxygen reduction reaction (ORR) electrocatalysts are key to reducing the cost of fuel cells and metal–air batteries. In this study, we synthesized Ce–Co-based N-doped porous carbon nanosheets (Ce–Co/N/C) by introducing a small amount of rare earth element Ce to improve the catalytic activity of Co-based electrocatalysts. Here, folic acid (FA) was used as a metal complex ligand, and Ce–Co/N/C was synthesized using a solvothermal method with molten salt template-assisted calcination. The resulting Ce–Co/N/C material exhibited superior ORR performance in alkaline media with a high half-wave potential of 0.893 V (vs. RHE), splendid stability and methanol resistance, which are significantly better than those of commercial 20% Pt/C. These favorable chemical properties are due to their advantageous composition and structure. Transmission electron microscopy and N₂ adsorption–desorption experiments showed that the catalyst has a large specific surface area and a hierarchical pore structure. X-ray photoelectron spectroscopy revealed that the change in Co binding energy after Ce doping indicates the adjustment of the Co electronic structure, which optimizes the adsorption/desorption of oxygen-containing intermediates and greatly improves the catalytic activity for oxygen reduction.