Edge activation of an inert polymeric carbon nitride matrix with boosted absorption kinetics and near-infrared response for efficient photocatalytic CO2 reduction

Abstract

The reduction of CO₂ into C₁ feedstocks (e.g., CO) by utilizing solar energy has attracted increasing attention for the efficient production of renewable energy. However, a significant challenge in the reduction of CO₂ is achieving high conversion efficiency due to the high CO dissociation energy of CO₂ and difficultly in accessing the surface of photocatalysts. Herein, we fabricated a polymeric carbon nitride (PCN) catalyst with hydroxyethyl groups grafted on its edge via a facile bottom-up strategy, facilitating the efficient surface absorption of CO₂ and lowering the CO₂ transformation energy barrier; this was accompanied with exceptional extended optical absorption ability to the near-infrared region and increase in the density of states at the Fermi level. Thus, concentrated CO₂ molecules could contact the surface of PCN and be easily activated; this resulted in an excellent CO production rate of up to 209.24 μmol h⁻¹ g⁻¹ in the modified PCN (i.e., 39.5-fold increase compared to that of pristine PCN) and a selectivity of 98.5% under white LED illumination, exceeding that of most PCN-based energy conversion systems reported to date. Notably, this PCN matrix also exhibited photocatalytic activity for the production of CO in the near-infrared region from 780 to 850 nm. These results pave the way for the development of structured photocatalysts with easy accessibility for CO₂ and broadband spectral response for the efficient photocatalytic reduction of CO₂.