Synergy of Carbon Nanotube-Supported Bimetallic Nanoalloy Catalysts in Rechargeable Lithium–Oxygen Batteries

Abstract

The ability to tune the electrocatalytic activities of oxygen reduction and evolution reactions at the air cathode is essential to reduce the overall overpotentials of rechargeable Li−air batteries. This report demonstrates a pathway to this ability by engineering the bimetallic composition of nanoalloy catalysts. This involves alloying Pt with oxyphilic Co in different bimetallic compositions by hydrothermal synthesis of the bimetallic alloy nanoparticles on carbon nanotubes, i.e., Pt 100−n Co n /CNT. The catalysts are characterized by different techniques, showing facecentered cubic alloy characteristics with crystalline and less-crystalline/ amorphous domains. The degree of oxidation of the Co components in the nanoalloys depends on the bimetallic composition, which is linked to the oxygen capacity of the nanoalloys. By discharging/charging performance testing in a rechargeable Li-O 2 battery cell, the overpotentials for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are shown to depend strongly on the bimetallic composition. Pt 50 Co 50 /CNT shows the lowest ORR and OER overpotentials, 160−170 mV, with respect to the thermodynamic potentials of Li/ Li 2 O 2 . This catalytic synergy is discussed in terms of the oxyphilicity of the catalysts, along with the calculated oxygen adsorption energies.

Alloy Drills Regulate MOF-Derived Carbon as a Recyclable Air Cathode

“…The lithium–oxygen (Li–O 2 ) batteries exhibit theoretical energy densities (116,80 W h kg –1 ) comparable to gasoline, far exceeding that of current commercial lithium-ion batteries. − As such, they hold broad application prospects. In aprotic Li–O 2 batteries, there has been extensive research on the stability of electrolytes and electrochemical reaction mechanisms. − The cathode of Li–O 2 batteries, as the core component, provides reaction sites for the three-phase reaction and space to accommodate the reaction products. , Its design significantly influences the capacity, cycling performance, and rate capability of Li–O 2 batteries. − Unfortunately, solid-insulating lithium peroxide (Li 2 O 2 ) products often block the porous cathode due to their sluggish kinetics in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), thereby reducing the cycling efficiency and capacity of Li–O 2 batteries. − Therefore, rationally designing the cathode structure and modulating catalytic activities are key to addressing this issue.…”