p-band regulation guides the free-standing porous carbon electrode for efficient Na-CO₂ batteries

The Na-CO₂ batteries with low-cost resources and high energy density have attracted huge attention in Mars and deep ocean exploration, but the slow CO₂ reduction reaction (CO₂RR) and CO₂ evolution reaction (CO₂ER) kinetics severely limit their practical application. Developing free-standing cathodes and understanding the relationship between the catalyst's active center and activity are essential to address long-standing challenges. This manuscript explores the promising metal-free porous carbon as a catalyst. The porous carbon network vertically grows on the surface of free-standing carbon paper to maximum exposure to the active site and optimization of electron/electrolyte transfer. Moreover, the active center of the carbon catalyst is optimized by introducing nitrogen or sulfur hetero-atom to regulate the p-band center, which steers the orbital hybridization and accelerates CO₂RR and CO₂ER kinetics The p-band optimized free-standing porous carbon electrode shows outstanding cycling of 1000 h with a small voltage gap of 1.04 V and a large energy efficiency of 71.2 % at 10 uA cm⁻². This study provides a new strategy for designing and fabricating p-band guided free-standing electrodes aiming at high-performance and wearable Na-CO₂ batteries. © 2024