Phase junction crystalline carbon nitride nanosheets modified with CdS nanoparticles for photocatalytic CO2 reduction

Abstract

Polymeric carbon nitrides exhibit massive potential for photocatalytic CO₂ reduction, especially the crystalline allotrope, namely, poly(triazine imide) (PTI), that possesses extended conjugation for fast charge exciton dissociation. However, pristine PTI suffers from poor visible light absorption, thus inhibiting critically the photocatalytic performance. Herein, crystalline carbon nitride nanosheets composed of PTI and melon phase junctions are in situ constructed from one-pot polycondensation of dicyandiamide and LiCl/KCl in air, and modified with CdS nanoparticles to create the double-junction-involved CCN/CdS hybrids. Physicochemical characterization reveals that CCN/CdS heterostructures exhibit broad visible-light harvesting, reinforced CO₂ adsorption/activation, and promoted separation and transfer of photoinduced charges. Therefore, the optimized CCN/CdS hybrid displays remarkable activity and high stability for photocatalytic CO₂-to-CO conversion at a rate of 52 μmol h⁻¹, together with an apparent quantum efficiency (AQE) of 10.8% at 420 nm. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) identifies the key intermediates during the CO₂ reduction process and thus endorses the proposal of the possible reaction mechanism.