Polyoxometalate Interlayered Zinc–Metallophthalocyanine Molecular Layer Sandwich as Photocoupled Electrocatalytic CO₂ Reduction Catalyst

Abstract

Developing efficient and robust heterogeneous metallophthalocyanine electrocatalysts for CO₂ reduction remains a challenge. Here, a general synthetic method of zinc-metallophthalocyanine (MPc) molecular layer/polyoxometalate (POM) sandwich lamellar material is developed, and thus improved performance of electrocatalytic and photocoupled electrocatalytic CO₂ reduction is achieved. The incorporation of POM could prevent the packing of MPc molecular layers from aggregation, which would be favorable to the exposure of active sites. The molecular layer sandwich catalyst presents superior CO₂ reduction activity, delivering the highest CO Faradaic efficiency (FE_CO) of 96.1% at -0.7 V vs RHE in dark field. Under light irradiation, over 93% FE_CO is achieved in a broad potential range from -0.6 to -0.9 V vs RHE with a maximum of 96.2%, and the carbon monoxide turnover frequency could exceed 2060 h^-1. Photoelectrochemical tests and luminescence characterizations reveal the molecular layer is beneficial for carrier separation during light irradiation; density functional theory calculations and electron paramagnetic resonance indicated a 2-fold enhancement of the external light field on the catalytic performance.