Boosting photocatalytic CO2 reduction to CH3OH through Pdx-modification on benzoxazine porous carbon spheres

Photocatalytic reduction of CO 2 to CH 3 OH is a promising strategy for the conversion of high value-added chemicals, and it is particularly important to overcome the serious problem of multiproton electronic coupling process. In this paper, we promoted the adsorption of CO 2 and the selectivity of the reduction products by modulating the presence form and the number of active sites of palladium on hierarchical porous carbon spheres. The Pd x -modified carbon spheres exhibited excellent CO 2 adsorption performance (2.17 mmol g −1 ) and photocatalytic reduction activity (CO yield of 14.35 μmol g −1 , CH 3 OH yield of 0.192 mmol L −1 ) while the loading amount of Pd was 0.05 at%, and the yields of the liquid-phase products can still remain around 97.3 % after ten cycles. The analysis results showed that the introduced Pd mainly consisted of 0-valent and + 2-valent states, and the proportion of + 2-valent Pd had a good correlation with the CH 3 OH yield. It was suggested that the + 2-valent Pd and pyridine nitrogen were the main active species and reaction sites. On one hand, pyridine nitrogen played an important role in improving the adsorption and activation of CO 2 , and promoting the reaction of H + with CO 2 to form COOH*. On the other hand, the introduction of Pd active sites not only significantly enhanced the transfer of electrons and holes, but also improved the generation of key intermediates for the conversion of CH 3 OH. This study will provide a new perspective for the design of highly selective photocatalysts.