One-dimensional van der Waals heterostructures as efficient metal-free oxygen electrocatalysts

TL;DR

This paper introduces one-dimensional van der Waals heterostructures with a CNT core and COF shell that serve as efficient, metal-free catalysts for oxygen redox reactions, significantly improving zinc-air battery performance.

Contribution

It reports a novel coaxial 1D vdWH structure with controllable doping and enhanced catalytic activity, advancing the design of efficient metal-free oxygen electrocatalysts.

Findings

Achieved high specific capacity of 696 mAh gZn-1 in zinc-air batteries.

Demonstrated significant catalytic activity enhancement due to controlled doping.

Enabled stable cycling performance under high current density.

Abstract

Two-dimensional covalent organic frameworks (2D-COFs) are an emerging family of catalytical materials with well-defined molecular structures. The stacking of 2D nanosheets and large intrinsic bandgaps significantly impair their performance. Here, we report coaxial one-dimensional van der Waals heterostructures (1D vdWHs) comprised of a carbon nanotube (CNT) core and a thickness tunable thienothiophene-pyrene COF shell using a solution based in situ wrapping method. Density functional theory calculations and in-operando and ex-situ spectroscopic analysis show that the carbon-sulfur region in the thienothiophene groups is the active catalytic site. The unique coaxial structure enables controllable n-doping from the CNT core to the COF shell depending on COF shell thickness, which lowers the bandgap and work function of COF. Consequently, the charge transfer barrier between the active catalytic site and adsorbed oxygen intermediates becomes lower, resulting in a dramatic enhancement in their catalytic activity for oxygen redox reactions. It enables a high-performance rechargeable zinc-air battery with a specific capacity of 696 mAh gZn-1 under a high current density of 40 mA cm-2 and excellent cycling stability. 1D vdWHs open the door to create multi-dimensional vdWHs for exploring fundamental physics and chemistry, as well as practical applications in electrochemistry, electronics, photonics, and beyond.