Rational design of porous Ru-doped CuO nanoarray on carbon cloth: Toward reversible catalyst layer for efficient Li-O₂ batteries

Until now, in case of Li-O₂ batteries, catalyst materials are applied by simple mixing with carbon black, which causes large overpotential due to limited active surface of the catalyst, leading to low energy efficiency and short cycle life. Accordingly, in previous studies, significant advances have been witnessed in the synthesis of various electrode materials with three-dimensional (3-D) structures for application in electrochemical energy storage devices. Herein, the 1-D@3-D catalyst layer design and efficient active site formation strategy help to enable an efficient Li-O₂ battery. In particular, it should be noted that the 1-D@3-D catalyst layer has great potential for maximizing the active contact area between the electrolyte and the catalyst materials and promoting the rapid diffusion of products and reactants through their stereoscopic structure. The 1-D Ru-doped CuO nanorod array on 3-D carbon cloth (Ru-CuO/RuO₂@CC) is demonstrated via 7,7,8,8-Tetracyanoquinodimethane-solution deposition, and thermal oxidation process. A comprehensive kinetic study using linear sweep voltammetry reveals that the Ru-CuO/RuO₂@CC has superior ORR/OER performance compared to a CuO nanorods-loaded carbon cloth and a CuO/RuO₂ nanoparticles-loaded carbon cloth. The Ru-CuO/RuO₂@CC as a catalyst layer combined cell is achieved 1.0 mA h cm⁻² (=3075 mA h g_c⁻¹) during 30 cycles with a low overpotential decay rate of 0.88% per cycle.