Dual role of g-C3N4 microtubes in enhancing photocatalytic CO2 reduction of Co3O4 nanoparticles

The activity of photocatalytic CO2 reduction (PCR) remains inadequate due to the thermodynamically stable CO2 molecules and sluggish carrier kinetics. This work simultaneously adopts active site and heterojunction engineering to collaboratively enhance PCR. A heterojunction of g-C3N4 microtube-supported Co3O4 nanoparticle has been developed through the hydrothermal pretreatment and calcination processes. The g-C3N4 microtubes play dual roles in enhancing PCR of Co3O4: (1) they act as a substrate to support Co3O4 nanoparticles, thereby making small size and good dispersion of Co3O4 nanoparticles. The Co active sites can be highly exposed to accept photogenerated electrons and capture CO2 molecules; and (2) the p-type Co3O4 nanoparticles and n-type g-C3N4 microtubes build a p–n junction. An internal electric field is created to expedite the charge transfer. As a result, the g-C3N4 microtube-supported Co3O4 nanoparticle affords a significantly high turnover number (TON) of 24.72, which is 24-fold higher than that of the pure Co3O4 and comparable to state-of-the-art photocatalysts.