Promoting Surface-Mediated Oxygen Reduction Reaction of Solid Catalysts in Metal–O₂ Batteries by Capturing Superoxide Species

Abstract

The oxygen reduction reaction (ORR) in aprotic electrolyte is the essential reaction in metal−oxygen batteries. Capturing and shifting the absorbed metal superoxide intermediates/products from a cathode surface is a long-standing challenge to clarify the ORR mechanism, accelerate the ORR, and improve the stability and energy density of metal−oxygen batteries. Herein, a bioinspired pathway in which cathode solid catalysts and soluble anthraquinone (AQ) molecules initiate an "enzyme−coenzyme" cooperative catalysis mechanism is developed to greatly boost the ORR activity of solid catalysts over 10-fold, in which AQ acts as a scavenger to capture and shift the absorbed superoxide species from the cathode surface to the aprotic electrolyte. Taking the lithium−oxygen (Li−O 2 ) battery as a model system, the cell discharge ORR mechanism is well illustrated and capacities are significantly improved over 3 times in the presence of AQ molecules. This concept represents the first demonstration of stabilizing and solvating superoxide species to substantially accelerate ORR catalysis of solid catalysts and enhance the performance of metal− O 2 batteries through biomimicking coenzyme-assisted reactions.

Nonmacrocyclic Iron(II) Soluble Redox Mediators Leading to High-Rate Li–O 2 Battery

“…1,2 The rechargeable lithium-oxygen (Li-O 2 ) battery is an ideal candidate owing to its high theoretical energy density, compared with that of gasoline. [3][4][5][6] Despite the significant progress in enhancing the capacity and cycling stability in recent years, [7][8][9][10][11][12][13][14][15][16][17][18] the rate performance of Li-O 2 battery, to date, is quite limited to usually <0.5× A× g −1 cathode , which is a challenge, especially, for high energy conversion applications. 4,5 In Li-O 2 battery, the energy is stored via the oxygen evolution reaction (OER) process and released via the oxygen reduction reaction (ORR) process, both of which occur on the cathode.…”

“…[22][23][24] For improving cycling stability, usually, two categories of electrocatalysts have been developed, that is, the heterogeneous catalysts decorated on carbon-based cathode [12][13][14][15][16][24][25][26] and the soluble redox mediators employed in electrolyte. [7][8][9][10][11]18,[27][28][29][30][31] With heterogeneous catalysts, the insulated Li 2 O 2 product of the ORR process densely deposits on the cathode surface, leading to separation of the catalytic sites from the Li 2 O 2 surface exposed to the electrolyte. 5,9,31,32 Accordingly, the OER process is retarded to some extent owing to the increased resistance of charge transfer via the insulated Li 2 O 2 deposit, leading to the limited rate capability.…”

Boosting the Performance of Graphene Cathodes in Na–O2 Batteries by Exploiting the Multifunctional Character of Small Biomolecules

“…[ 7–9 ] Hence, small‐size particles or film‐like deposition products similar to those observed in Figure 2e were associated to a surface‐mediated mechanism. Nevertheless, the prevalence of this mechanism over the solution‐mediated has been mainly correlated with the applied current density [ 36 ] or the use of additives [ 37 ] rather than the chemistry of the cathode. In our previous work, an increased interaction of reduce oxygen species with the phosphate groups of AMP molecules was suggested to promote a surface‐mediated mechanism in A‐EEG aerogels.…”

Voltammetric monitoring of a solid-liquid phase transition in N,N,N′,N′-tetraoctyl-2,6-diamino-9,10-anthraquinone (TODAQ)

“…Anthraquinone and more generally quinone-type redox materials are very commonly employed for a range of applications such as solid-state intercalation cathode materials for Li-ion batteries [26,27], homogenous catalysts for nonaqueous Li-air batteries [28,29] aqueous redox catalysis of oxygen [30,31]. In acidic media, a chemically reversible 2electron 2-proton reduction occurs with formation of the corresponding anthraquinol [32] (see Eq.…”