Boosting Energy Efficiency and Stability of Li-CO2 Batteries via Synergy between Ru Atom Clusters and Single-Atom Ru-N4 sites in the Electrocatalyst Cathode

The Li-CO2 battery is a novel strategy for CO2 capture and energy-storage applications. However, the sluggish CO2 reduction and evolution reactions cause large overpotential and poor cycling performance. Herein, a new catalyst containing well-defined ruthenium (Ru) atomic clusters (Ru-AC) and single-atom Ru-N-4 (Ru-SA) composite sites on carbon nanobox substrate (RuAC+SA@NCB) (NCB = nitrogen-doped carbon nanobox) is fabricated by utilizing the different complexation effects between the Ru cation and the amine group (-NH2) on carbon quantum dots or nitrogen moieties on NCB. Systematic experimental and theoretical investigations demonstrate the vital role of electronic synergy between Ru-AC and Ru-N-4 in improving the electrocatalytic activity toward the CO2 evolution reaction (CO2ER) and CO2 reduction reaction (CO2RR). The electronic properties of the Ru-N-4 sites are essentially modulated by the adjacent Ru-AC species, which optimizes the interactions with key reaction intermediates thereby reducing the energy barriers in the rate-determining steps of the CO2RR and CO2ER. Remarkably, the RuAC+SA@NCB-based cell displays unprecedented overpotentials as low as 1.65 and 1.86 V at ultrahigh rates of 1 and 2 A g(-1), and twofold cycling lifespan than the baselines. The findings provide a novel strategy to construct catalysts with composite active sites comprising multiple atom assemblies for high-performance metal-CO2 batteries.

Automated summary

Researchers have developed a new catalyst consisting of well-defined ruthenium atomic clusters and single-atom Ru-N-4 composite sites on a carbon nanobox substrate. They found that the electronic synergy between Ru-AC and Ru-N-4 plays a vital role in improving the electrocatalytic activity for CO2 evolution reaction and CO2 reduction reaction.