Regulating the spin density of CoIII using boron-doped carbon dots for enhanced electrocatalytic nitrate reduction

Controlling the electron spin state on the catalyst surface can regulate the reaction activity, rate, and selectivity of surface reactions. However, there are still many challenges in exploring new strategies for electron spin regulation and mechanisms of the electron spin effect. Herein, we reported a method of using BCDs loading to change the electron spin density of magnetic Co3O4. Octahedral Co3+(O-h)-O with a t(2g)(6)e(g)(0) configuration transformed into Co2+(O-h)-O with a t(2g)(5)e(g)(2) configuration after BCDs loading showed excellent activity in the electrocatalytic nitrate reduction reaction, achieving a maximum NH4+ Faradaic efficiency of 94.6 +/- 0.9% and high stability. Experimental results and theoretical calculations have found that high activity is attributed to the spin density regulation changing the rate-determining step and reducing the energy it needs to overcome. This work expands the spin density regulation methods and provides a new perspective for understanding the mechanisms of carbon dot materials in electrocatalytic reactions.