Pd-modified g-C3N4 with internal donor-acceptor motifs for photocatalytic CO2 reduction to tunable syngas

The conversion of CO2 and H2O to value-added syngas (CO and H-2) using light energy is a sustainable strategy for carbon cycle, but efficient CO2 reduction with tunable CO/H-2 ratios remains a huge challenge. Here, we designed a Pd modified g-C3N4 with a localized donor-acceptor (D-A) system by depositing Pd on cyano-modified g-C3N4 (Cy-CN). The electron-rich cyano group acts as an electron acceptor and the coordinated N atoms act as electron donors, which collaboratively contributes to an efficient charge transfer and separation. Loading Pd nano-particles not only further improves the charge transfer efficiency induced by the Schottky junction but also enhances the hydrogen intermediates adsorption activation, allowing the modulation of the CO/H-2 ratio. The experimental results show that efficient CO2 reduction to syngas was achieved with yield of 493.95 mu mol center dot g(-1) and the molar ratio of CO/H-2 can be adjusted from 1:9.29 to 1:2.22 under visible light irradiation. This work provides a promising strategy for the simple and efficient photocatalytic production of tunable syngas from CO2 reduction over g-C3N4 localized D-A systems in synergy with metal sites.