Exceptional photocatalytic activities for CO2 conversion on Al[sbnd]O bridged g-C3N4/α-Fe2O3 z-scheme nanocomposites and mechanism insight with isotopesZ

Abstract

It’s highly desired to design and fabricate effective Z-scheme photocatalysts by promoting the charge transfer and separation. Herein, we firstly fabricated the ratio-optimized g-C3N4/α-Fe2O3 nanocomposites by adjusting the mass ratio between two components through a simple wet-chemical process. The resulting nanocomposites display much high photocatalytic activities for CO2 conversion and phenol degradation compared to bare α-Fe2O3 and g-C3N4. Noteworthily, the photocatalytic activities are further improved by constructing AlO bridges, by 4-time enhancement compared to those of α-Fe2O3. Based on the steady-state surface photovoltage spectra, transient-state surface photovoltage responses, photoelectrochemical I-t curves and the evaluation of produced OH amounts, the exceptional photoactivities of AlO bridged g-C3N4/α-Fe2O3 nanocomposites are attributed to the significantly promoted charge transfer and separation by constructing the g-C3N4/α-Fe2O3 heterojunctions and the AlO bridges. Moreover, the charge transfer and separation of this photocatalyst have been confirmed to obey the Z-scheme mechanism, as supported by the single-wavelength photocurrent action spectra and single-wavelength photoactivities for CO2 conversion. Furthermore, the mechanism of the photocatalytic CO2 conversion has been elaborately elucidated through the electrochemical reduction and the photocatalytic experiments especially with isotope 13CO2 and D2O, that the produced H atoms as intermediate radicals would dominantly induce the conversion of CO2 to CO and CH4.