Axial modulation of catalysis mechanism via charge-asymmetric for enhanced electrocatalytic performance toward hydrogen and oxygen evolution reactions

Abstract

Designing efficient, stable, and nonprecious metal bifunctional catalysts is warranted for realizing the industrial application of electrocatalytic overall water splitting. Herein, we report a new catalyst (CoFe/SNC) for the HER and OER. The active site of catalysis composed of two charge-asymmetric Co/Fe atoms could axial modulation of the catalysis mechanism, thus improving the kinetics of the HER and OER. Moreover, the use of hollow porous carbon spheres as catalyst support not only enhances the distribution of Co/Fe atoms but also improves the mass transfer during the HER and OER processes. Therefore, the CoFe/SNC displays a good alkaline HER and OER activity with a small overpotential of 96.2 mV and 285.8 mV at 10 mA cm−2, respectively. Theoretical calculations reveal that the Fe atoms with optimal absorption energy for the hydrogen intermediate and the Co centers with a reduced energy barrier for the rate-determining step are the active sites for HER and OER, respectively. Additionally, the synergistic effect of Co/Fe dual-atoms could effectively optimize the intermediate adsorption of Co/Fe-N4 sites and improve the barriers of HER and OER activity and stability. This study provides valuable insight for designing bifunctional alkaline water-splitting electrocatalysts.