Summary
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 gc−1) during 30 cycles with a low overpotential decay rate of 0.88% per cycle.
For commercialization of zinc-air batteries, it is important to replace expensive noble metal catalysts with inexpensive carbonaceous materials. Herein, an efficient oxygen evolution reaction (OER) catalyst composed of a unique porous tunnel carbon cube and cobalt nanoparticles (Co@NPCC) was fabricated to facilitate oxygen diffusion and create electron conduction networks. As an OER catalyst for zinc-air batteries (ZABs), the resulting Co@NPCC demonstrate enhanced OER activity, similar to that of the benchmark RuO 2 . In OER performance, Co@NPCC exhibits the excellent mass activity of 49.9 mA mg À1 at overpotential (η) of 0.47 V and the high current density of 91.5 mA cm À2 at 1.75 V (vs RHE), compared to commercial RuO 2 catalysts. The use of Co@N-PCC as the OER catalyst for ZAB maintains stable charge overpotential with as little as 0.05 V variation during 250 cycles, which extends the stable discharge-charge cycle performance compared to RuO 2 . This work highlights a facile approach to fabricate OER catalysts without noble metals for enabling stable charge state and long life ZABs.
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