From Ru to RuAl intermetallic/Ru heterojunction: Enabling high reversibility of the CO2 redox reaction in Li-CO2 battery based on lowered interface thermodynamic energy barrier

The impenetrable thermodynamic barrier of the Li2CO3 decomposition reaction has been the challenge to ach-ieve high reversibility of Li-CO2 batteries. Ruthenium-based nanomaterials represent one class of promising cathode catalysts, but are still challenged by the limited catalytic activity for reducing the thermodynamic energy barrier of the decomposition of Li2CO3. Herein, we clarify that the intrinsic catalytic activity of Ru can be distinctly enhanced by screening RuAl intermetallic and interpenetrating-phase trimodal porous RuAl/Ru het-erojunction (NP-RuAl/Ru). The NP-RuAl/Ru with multilevel pore channels is straightforwardly made through driving the phase and microstructure reconstruction upon controllable dealloying of partial Al from a Ru-Al master alloy. Density functional theory simulations disclose that the RuAl/Ru interface can dramatically lower the Gibbs free energy of the Li-dissociation related intermediate steps in the CO2 evolution process owing to the intrinsically high catalytic activity of RuAl intermetallic and strong interface coupling. The multilevel network skeleton with rich nano-interfaces provides high density of active sites, the fluent pathway for both the electron and mass transportation, as well as ample space for discharge product uptaking. In situ differential electro-chemical mass spectrometry demonstrates that the molar ratio of evolved-CO2 to transferred-electrons in the charging process is-0.73 closing to the theoretical value of 0.75, attesting the high reversibility of the CO2 redox reaction over NP-RuAl/Ru in Li-CO2 battery. The well-crafted NP-RuAl/Ru catalyst delivers a lower voltage gap stabilized at-1.25 V for 1400 h (nearly two months) at 200 mA g-1. Such "the phase and structure recon-struction" protocol in the light of dealloying unveils a new paradigm to build the highly efficient intermetallic-based electrocatalysts incorporated with non-precious metals for Li-CO2 batteries and other energy-related applications.