Dual-type atomic Ru promoted bifunctional catalytic process realizing ultralow overpotential for Li-O2 batteries

Developing well-defined catalysts to ameliorate overpotential and cycling capability is imperative for high-performance Li-O2 batteries. However, conventional catalysts face fundamental challenges that ORR and OER with different rate-determining steps are catalyzed by the same active center, inevitably weakening the selectivity and activity. Herein, we report a cross-scale catalyst with ultrafine RuPt nanoparticles and surrounding RuPt pairs on porous carbon (RuPt NPs@RuPt-N-C). The planted Ru single atoms within Pt nanoparticles and carbon matrix contribute to a fresh bifunctional catalytic mechanism for enhancing ORR/OER catalytic kinetics. As a proof-of-concept application in Li-O2 batteries, this catalyst realizes extremely low overpotentials of only 0.43 V and superior cyclic stability of 209 cycles at 200 mA g−1. Experimental and computational results disclose that for Pt NPs@Pt-N-C without Ru functionalization, only Pt-N-C works as ORR/OER active centers. By contrast, for RuPt NPs@RuPt-N-C, due to downshifted d-band center and enhanced charge transfer with LiO2 intermediate, the Pt nanocrystals are fully activated by Ru atoms, making RuPt nanocrystals as preferable ORR kinetics promoter for the formation of easily-decomposed nanoflower Li2O2. Moreover, adjacent RuPt pairs with weakened O2 affinity can work as major OER center, contributing to accelerating the following Li2O2 decomposition. This work expands the frontier of cross-scale electrocatalysts with tailored bifunctional catalysis properties for other electrocatalytic fields.