Chinese Journal of Catalysis ›› 2022, Vol. 43 ›› Issue (5): 1238-1246.DOI: 10.1016/S1872-2067(21)63946-3

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Interfacial engineering of heterogeneous molecular electrocatalysts using ionic liquids towards efficient hydrogen peroxide production

Zixun Yu, Chang Liu, Yeyu Deng, Mohan Li, Fangxin She, Leo Lai, Yuan Chen(), Li Wei()   

  1. School of Chemical and Biomolecular Engineering, The University of Sydney, Darlington, New South Wales, Australia
  • Received:2021-08-29 Accepted:2021-09-14 Online:2022-05-18 Published:2022-03-23
  • Contact: Yuan Chen, Li Wei
  • Supported by:
    Australian Research Council under the Future Fellowships Scheme(FT160100107);Discovery Programme(DP180102210);University of Sydney under the Commercial Development and Industrial Partnership(CDIP-2020-32)

Abstract:

Efficient and selective oxygen reduction reaction (ORR) electrocatalysts are critical to realizing decentralized H2O2 production and utilization. Here we demonstrate a facile interfacial engineering strategy using a hydrophobic ionic liquid (IL, i.e., [BMIM][NTF2]) to boost the performance of a nitrogen coordinated single atom cobalt catalyst (i.e., cobalt phthalocyanine (CoPc) supported on carbon nanotubes (CNTs). We find a strong correlation between the ORR performance of CoPc/CNT and the thickness of its IL coatings. Detailed characterization revealed that a higher O2 solubility (2.12 × 10-3 mol/L) in the IL compared to aqueous electrolytes provides a local O2 enriched surface layer near active catalytic sites, enhancing the ORR thermodynamics. Further, the hydrophobic IL can efficiently repel the as-synthesized H2O2 molecules from the catalyst surface, preventing their fast decomposition to H2O, resulting in improved H2O2 selectivity. Compared to CoPc/CNT without IL coatings, the catalyst with an optimal ~8 nm IL coating can deliver a nearly 4 times higher mass specific kinetic current density and 12.5% higher H2O2 selectivity up to 92%. In a two-electrode electrolyzer test, the optimal catalyst exhibits an enhanced productivity of 3.71 molH2O2 gcat-1 h-1, and robust stability. This IL-based interfacial engineering strategy may also be extended to many other electrochemical reactions by carefully tailoring the thickness and hydrophobicity of IL coatings.

Key words: Hydrogen peroxide, Ionic liquid, Oxygen reduction reaction, Single-atom catalyst, Heterogeneous molecular catalyst