Adjacent atomic cobalt sites anchored on carbon foam as a self-supporting electrode for efficient hydrogen evolution

There are still great challenges in developing single atom materials with high catalytic activity for the hydrogen evolution reaction (HER). The synergistic effect between adjacent single atom sites due to the high site density is still unclear. Herein, a MOF-derived strategy is proposed based on inkjet printing technology to synthesize carbon foam supported adjacent Co single atom sites (Co-N/CMF-20) as a self-supporting electrode for the HER. The features of inkjet printing with direct writing and computer control help to reduce the formation of clusters or nanoparticles, thus endowing the self-supporting electrode with high atomic site density. The results show that the single atoms are close to each other, thus forming adjacent but dispersed Co sites. Density functional theory calculations suggest that the synergistic effect between adjacent single atoms creates favorable charge transfer and moderate binding with HER intermediates, thus leading to enhanced catalytic activity. As a result, Co-N/CMF-20 affords 10 mA cm⁻² current density with low overpotentials of 41.3 and 59.6 mV in acidic and alkaline HERs, respectively, highlighting the superiority of the adjacent site effect. This work provides a new insight for the synthesis of self-supporting single atom catalysts.