New heterojunctions of CN/TiO2 with different band structure as highly efficient catalysts for artificial photosynthesis

To store solar energy into chemical energy and ameliorate over-emission of CO2 in modern society, the promising photoelectrocatalytic reduction of CO2 into multicarbon products (C2+) has inspired scientists to discover new efficient catalysts. Herein, a series of new heterojunctions of polypyrrole/TiO2 (PTCN-X, X is pyrolytic temperature) were prepared by a facile method of in-situ oxidizing polymerazation of pyrrole onto the surface of TiO2 and subsequently treating with temperature-controlled pyrolysis. An interesting phenomenon was discovered that the p-n heterojunction of PTCN gradually transferred to n-n heterojunction of PTCN-400. The optimal n-n heterojunctions of PTCN-400 have the highest selectivity of C2+ products (71.4 %) under iirridiation at -1.2 V. Further investigation reveals that the band structure of PTCN-X heterojunctions can be tuned by various pyrolytic temperature to form more defects and pyridine-N active sites, which enhances separation efficiency of photogenerated electron-holes and selectivity of C2+ products.

Automated summary

A series of heterojunction catalysts of polypyrrole/TiO2 were prepared by in-situ oxidizing polymerization of pyrrole onto TiO2 and subsequent pyrolysis treatment, with the optimal n-n heterojunction of PTCN-400 showing the highest selectivity for C2+ products under irradiation at -1.2 V. Tuning the band structure of PTCN-X heterojunctions by various pyrolytic temperatures enhances the selectivity of C2+ products through the formation of more defects and pyridine-N active sites.