Distorted carbon nitride nanosheets with activated n → π* transition and preferred textural properties for photocatalytic CO2 reduction

Ultrathin polymeric carbon nitride nanosheets (PCN-NSs) are considered as a promising semiconductor photocatalyst for CO2 reduction, but the achieved efficiency is still unsatisfactory. Herein, a methanol-mediated steam delaminating strategy is demonstrated to fabricate distorted PCN-NSs (d-PCN-NSs) with activated n-pi* electron transition and favorite textural properties. The ultrathin d-PCN-NSs can absorb optical spectrum extending to 700 nm, accelerate separation and transportation of photoinduced charge carriers, and deliver rich disclosed active sites for CO2 adsorption/activation. Compared to that of pristine PCN and plane PCN-NSs, the CO2-to-CO conversion activity of d-PCN-NSs is enhanced by 35.7 and 4.4 times, respectively, displaying a high apparent quantum efficiency (AQE) of 3.8% under photoirradiation at 420 nm. Of note, the d-PCN-NSs photocatalyst can still catalyze a CO2 photoreduction reaction under 660 nm illumination. Based on the key catalytic-active intermediate (i.e., COOH*) determined by in-situ diffuse reflectance infrared Fourier transform spectroscopy, the possible mechanism of the tandem CO2 photoreduction catalysis is proposed. (C) 2021 Elsevier Inc. All rights reserved.