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 H2) using light energy is a sustainable strategy for carbon cycle, but efficient CO2 reduction with tunable CO/H2 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 nanoparticles 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/H2 ratio. The experimental results show that efficient CO2 reduction to syngas was achieved with yield of 493.95 µmol·g−1 and the molar ratio of CO/H2 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.