Surprisingly advanced CO2 photocatalytic conversion over thiourea derived g-C3N4 with water vapor while introducing 200–420 nm UV light

• First introduction of 200–420 nm UV light for CO2 photoreduction over g-C3N4.
• Interesting alternation in CO2 reduction performance between TCN and UCN.
• Wonderful activity and renewability of TCN for CO2 conversion >200 nm UV–vis light.

200–420 nm UV light was for the first time introduced for CO2 photocatalytic reduction over graphitic carbon nitride (g-C3N4). It was surprisingly found that thiourea derived g-C3N4 (TCN), which showed inferior activity in CO2 reduction under visible light irradiation, exhibited more remarkable CO2 conversion efficiency under >200 nm light irradiation compared to g-C3N4 synthesized from urea (UCN) and commercial TiO2 (P25). Also, the highest selectivity to CO2 conversion was observed over TCN while P25 showed the most prominent H2 production followed by UCN. Through a series of characterizations, the more abundant –NHx species that were responsible for CO2 activation, the enhanced reducing ability of photo-excited electrons under UV light and the higher photo-exited electron-hole separation efficiency were supposed to contribute to the excellent CO2 photocatalytic reduction activity of TCN under >200 nm UV–vis light irradiation, whilst its visible-light activity was relatively weak because of its limited surface area. Further, TCN performed a wonderful stability with a good record of circle tests in this irradiation condition.

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