Nanocarbon‐Based Electrocatalysts for Rechargeable Aqueous Li/Zn‐Air Batteries

Abstract

Zn-air batteries have become the most attractive energy storage devices because of their extremely high theoretical energy density, which enables electric vehicles to drive long range. However, current achievements still suffer from poor cycle life, low practical energy density, low round-trip efficiency, and high manufacturing costs. One of the key challenges is the sluggish kinetics of oxygen electrochemistry during discharge and charge cycles. Thus, significant breakthroughs in design and synthesis of efficient electrocatalysts for the oxygen redox reaction are highly demanded. Nanocarbons, especially heteroatoms doped nanocarbons, are potential oxygen reduction reaction (ORR) catalysts due to the reasonable balance between catalytic activity, durability, and cost. Importantly, by introduction of transition metal nanoparticles, spinel oxides, layered-double hydroxides, perovskite oxides, and other metal oxides, the constructed nanocarbon-based materials could deliver promising bifunctional ORR and oxygen evolution reaction (OER) catalytic properties, which could be employed as air-cathode materials to improve energy storage performances, even to get commercialized. Here, an overview of the recent progress of nanocarbon-based electrocatalysts as air-cathode materials for rechargeable aqueous Li/Zn-air batteries is provided, aiming to highlight the benefits and issues of nanocarbon-based electrocatalysts as well as to outline the most promising results and applications so far.[a] Prof.

Electrocatalysis of Oxygen on Bifunctional Nickel‐Cobaltite Spinel

“…In fact, composite catalysts based on transition metal oxides and carbon (in particular, nitrogen-doped carbonaceous material) have received increasing attention owing to their synergistic catalytic activity. [33,[38][39][40][41][42] Recently, our group investigated electrospun carbon nanofibers (CNF) decorated with both cobalt oxide and metallic cobalt (CoOÀ Co/CNF) [25] or loaded with nickel and cobalt (both in the metallic and oxide forms), [43] as bifunctional air electrodes, which presented good reversibility and stability. In the present research the latter catalyst (NiCo-loaded CNFs), [43] was further oxidized with the aim of synthesizing the pure spinel structure (NiCo 2 O 4 ) supported on the electrospun CNFs.…”

Nanocarbon-based metal-free and non-precious metal bifunctional electrocatalysts for oxygen reduction and oxygen evolution reactions

“…Despite heteroatoms doping/functionalization metal-free nanocarbon materials have been proved to be an effective for bifunctional oxygen catalysis in alkaline solution, they cannot remain electrochemical stability under the oxidative OER condition. Transition metal (including alloy, oxides, hydroxides, sulfides, phosphides) supported on nanocarbon or heteroatoms doping/ functionalization nanocarbon materials have been widely explored as oxygen bifunctional NPMCs and hope to solve the poor-stability of metal-free catalysts [34,36,92,121].…”

Doped Nanocarbons Derived from Conducting Polymers toward ORR Electrocatalysts

“…However, when the ORR is two‐electron transfer reaction, in addition to the formation of water and hydroxyl ions in the solution, large amounts of hydrogen peroxide are also generated. The cathode oxygen reduction process in metal‐air batteries is similar to the principles of fuel cells …”