Understanding Boosted Selective CO_2-to-CO Photoreduction with Pure Water Vapor over Hierarchical Biomass-Derived Carbon Matrix

摘要

Solar-driven CO_2 reduction reaction (CO_2RR) with water into carbon-neutralfuels is of great significance but remains challenging due to thermodynamicstability and kinetic inertness of CO2. Biomass-derived nitrogen-doped carbon(N-Cb) have been considered as promising earth-abundant photocatalysts forCO_2RR, although their activities are not ideal and the reaction mechanism isstill unclear. Herein, an efficient catalyst is developed for CO_2-to-CO conversionrealized on diverse N-Cb materials with hierarchical pore structures. Itis demonstrated that the CO_2-to-CO conversion preferentially takes place onpositively charged carbon atoms next to pyridinic-N using two representativestreated pollens with the largest difference in pyridinic-N density and Ncontent as model photocatalysts. Systematic experimental results indicatethat surface local electric field originating from charge separation can beboosted by hierarchical pore structures, doped N, as well as pyridinic-N.Mechanistic studies reveal that positively charged carbon atoms next topyridinic-N serve as active sites for CO2RR, reduce the energy barrier on theformation of CO*, and facilitate the CO2RR performance. All these benefitscooperatively contribute to treated chrysanthemum pollen catalyst exhibitingexcellent CO formation rate of 203.2 μmol h~（?1） g~（?1） with 97.2% selectivity inpure water vapor. These results provide a new perspective into CO_2RR onN-C_b, which shall guide the design of nature-based photocatalysts for highperformancesolar-fuel generation.