Cobalt porphyrin and silver dual active sites on g-C3N4 for boosting photocatalytic CO2 reduction

This dual-site strategy offers a new route for steering CO 2 reduction and catalyst design. • Synergistic dual sites boost charge transfer, CO 2 adsorption, and *OCH 3 formation. • Cobalt-based porphyrin (CoTCPP) sites on graphitic carbon nitride accounts for CO 2 reduction into CH 4 . • Ag/CoTCPP dual sites achieve 340-fold higher than graphitic carbon nitride photocatalyst for CO production. Graphitic carbon nitride (g-C 3 N 4 ) was identified as a highly promising catalyst for the photocatalytic reduction of CO 2 . However, its performance was limited by a lack of highly efficient active sites for photogenerated electron accumulation and CO 2 adsorption/activation. In this study, a cobalt porphyrin (CoTCPP) and Ag dual-active-site co-modified CNN (CoTCPP/Ag/CNN) was prepared for boosting photocatalytic CO 2 reduction. When the Ag loading was 1 wt% and the CoTCPP loading was 0.5 wt%, the catalyst exhibited optimal activity, with CO and CH 4 yields reaching 67.8 μmol g −1 ·h −1 and 10.4 μmol·g −1 ·h −1 , respectively, whereas pure CNN produced only 0.2 μmol·g −1 ·h −1 of CO. The experimental results indicated that the dual-type sites not only effectively enhanced the photo-generated carrier mobility, but also significantly strengthened the CO 2 adsorption and activation, and promoted the formation of the key intermediate *OCH 3 , thereby markedly improving the efficiency of CO 2 photoreduction. This study proposed a novel strategy for the rational design of dual active sites on catalyst surfaces and the regulation of CO 2 reduction reaction pathways.