Modulating charge separation of Ce–TiO2 aerogel supported on chitosan derived ordered porous carbonaceous frameworks for promoting CO2 photoreduction activity

Abstract

Developing efficient photocatalysts with low cost, high performance, and high selectivity is essential and imperative for CO2 conversion and utilization, yet it remains a big challenge. Herein, a novel Ce-doped TiO2 aerogel with oxygen vacancy anchored on the oriented carbonaceous (Ce–TiO2@CS) is synthesized by the sol-gel technique, combined with the freeze casting, supercritical drying technique, and heat treatment processes. The Ce–TiO2@CS aerogel has a typical aerogel-like structure, with the Ce–TiO2 aerogel anchored on the oriented porous carbon, rendering a large BET-specific surface area of 124 m2/g, which leads to enhanced photocatalytic activity. The Ce-doping into the pristine TiO2 results in impurity levels within the band gap, which extends the light response range to the visible light region. In addition, the rapid combination of electrons and holes is prevented via the two-phase microstructures and rapid transfer rate of electrons within the oriented porous carbon. The yields of CH4 and CO are as high as 9.45 μmol h−1 g−1 and 42.26 μmol h−1 g−1, respectively, which are 28.6 and 2.46 times higher than those of pristine TiO2 aerogel under simulated solar spectrum conditions without any sacrificial agents or co-catalysts, The density functional theory (DFT) calculation shows that larger C–O bonds of CO2 molecule and more negative adsorption energy have occurred on the Ce–TiO2@CS aerogel, indicating that the CO2 activation has been enhanced, which greatly improves the CO2 photoreduction activity. This work may guide the designing of aerogel-based photocatalysts for CO2 photocatalytic reduction.