Regulating spin states via building asymmetric CoTe dual-atom pairs for efficient bifunctional oxygen electrocatalysis in zinc-air batteries

Developing a facile pyrolysis-etching strategy to prepare asymmetric Co-Te/NC DAC. • Te atoms drive the transition of Co(III) from intermediate-spin to high-spin state. • High-spin Co(III) enhances the adsorption-desorption equilibrium of O-intermediates. • Co 3 d -Te 4 p orbitals hybridization modulates local charge distribution of Co sites. • The Co-Te/NC-based aqueous zinc-air battery shows a high capacity of 805 mAh g −1 . Atomically dispersed cobalt‑nitrogen‑carbon (Co-N-C) catalysts are highly efficient candidates for oxygen reduction/oxygen evolution reaction (ORR/OER). However, their catalytic activity is limited by the symmetric electron distribution between the metal center and the adjacent N atoms with high electronegativity, which results in suboptimal adsorption energy for the reaction intermediates. To overcome this limitation, asymmetric coordination engineering is employed to introduce the non-metal tellurium (Te) into Co-N-C, constructing a heteronuclear Co-Te/NC dual-atom catalyst that regulate the interaction between Co sites and oxygen intermediates. Magnetic measurements and theory calculations indicate that Te atoms induce spin state transition in the Co(III) active center, driving electron transfer from Te to Co. The high-spin Co(III) in the Co-Te/NC facilitates the efficient adsorption and activation of intermediates while accelerating the product desorption. Additionally, asymmetric Co Te dual atom pair enhances d-p orbital hybridization, optimizing the adsorption energy of intermediates. Therefore, Co-Te/NC exhibits an ORR half-wave potential of 0.922 V and a low OER overpotential of 350 mV. Co-Te/NC-based aqueous zinc-air batteries (ZABs) can achieve a peak power density of 125 mW cm −2 and maintain stable voltage over 660 charge-discharge cycles. Co-Te/NC-based flexible ZABs show minimal output voltage fluctuations at varying folding angles, demonstrating excellent mechanical flexibility. This work offers new insights into the precise regulation of the microenvironment of atomically dispersed catalysts. Download: Download high-res image (197KB) Download: Download full-size image