Constructing cascaded multi-heterojunction system with ultrafast electron transfer for enhanced photocatalytic CO2 reduction

The development of effective photocatalysts powered by visible light to convert carbon dioxide into chemical fuels has received much attention. Graphene nanoribbons exhibit tunable optical and electronic bandgaps, granting them remarkable semiconductor characteristics, including elevated carrier mobility and pronounced exciton effects. Herein, we have prepared cove-type graphene nanoribbons (cGNRs-DiCOOH) with post-functionalization capabilities for the first time, which have high charge mobility and can effectively improve the charge separation efficiency. Hence, we have designed a cascaded multi-heterojunction system of carbon-based material (Complex: cGNRs-DiCOOH@TCPP-Fe@TiO₂@CdS) to improve the reactivity of CO₂ molecules, namely, cGNRs-DiCOOH and TCPP-Fe were coupled with the carboxyl-containing compound tris-(2-aminoethyl)amine based on the acylation reaction, and TiO₂ and CdS were added during the coupling process. A study was conducted to investigate the photocatalytic CO₂ reduction performance of the Complex material, which exhibited excellent CO₂ reduction efficiency with a CO yield as high as 644 µmol/g/h. Compared with the cGNRs-DiCOOH sample, the yield was increased by 25 times. The photocatalytic process was revealed by dynamically monitoring the active species and reaction intermediates at the active sites of the Complex using in situ Fourier transform infrared and X-ray photoelectron spectroscopy. This strategy provides new insights into combining two-dimensional carbon nanomaterials with photocatalysts to construct cascade multi-heterojunctions for solar-to-fuel conversion.

Graphical Abstract

Novel cove-type graphene nanoribbons (cGNRs-DiCOOH) were developed with post-functionalization to boost photocatalytic CO₂ reduction. Combining the advantages of cGNRs-DiCOOH, titanium dioxide (TiO₂), cadmium sulfide (CdS), and tetra-(4-carboxyphenyl)-porphyrin-Fe(III) (TCPP-Fe) created a Complex material with cascaded mult-heterojunctions of multi-electron transfer pathways with superior CO₂ conversion efficiency, achieving a CO yield of 644 µmol/g/h. This strategy provides new insights into combining two-dimensional carbon nanomaterials with photocatalysts to construct cascade multi-heterojunctions for solar-to-fuel conversion.