CO2 chemisorption and activation on carbon nitride with less amino groups boost CO2 photoreduction

Abstract

CO₂ chemisorption and activation are two crucial factors that can significantly impact the overall CO₂ conversion efficiency. However, achieving effective modulation of these processes in metal-free photocatalysts has proven to be challenging. In this study, we present a novel approach for activating CO₂ molecules by selectively removing some amino groups at the boundary of carbon nitride (CN). By doing so, we observed a concentration of photogenerated electrons at the nitrogen atoms neighboring the eliminated –NH₂ group. This electron concentration enhances the chemisorption and activation of CO₂, resulting in lowered energy barriers for the rate-determining step from CO₂ to *COOH. Interestingly, we found that only the nitrogen atoms adjacent to the removed –NH₂ group in CN serve as catalytic sites, in contrast to all the nitrogen atoms neighboring the –NH₂ group in CN–NH₂. As a result, CN exhibits superior catalytic efficiency, with a turnover frequency (TOF) for CO that is 23.11 times higher than that of CN–NH₂ under identical conditions.