Heightening polyoxometalate encapsulation efficiency for biaxial strain-induced catalytic activity boosting

Abstract

Controllable assembly of polyoxometalates (POMs) in confined nanochannels is crucial to understand the host-guest structures and tailor the emerging properties for applications. Here, we report the encapsulation of polyoxometalates inside single-walled carbon nanotubes (SWNTs) for target catalytic regulation. Theoretical modeling predicts the confined polyoxomolybdates are able to induce biaxial tensile strains of SWNTs for more stable interaction with iron phthalocyanine (FePc) and tailor the charge distribution and coordination environment of targetable FeN₄ sites, leading to improved catalytic activity toward oxygen reduction reaction (ORR). The polyoxomolybdates are confined in the SWNTs via redox-driven encapsulation mechanism with a POM encapsulation efficiency of about 21 %. The constructed FePc/SWNT@POM molecule catalyst exhibits a high half-wave potential of 0.90 V, excellent stability and methanol tolerance in alkaline medium. The zinc-air battery also presents prominent charge-discharge ability and long-term durability over 400 h with a peak power density of 190.8 mW cm^–2.