High-efficient separation of photogenerated carriers in S-scheme BiOI@TpPa-1 heterojunction for enhanced photocatalytic CO2 reduction: crystal face engineering and DFT calculations

Abstract

Energy shortage and ecological pollution have become important issues in global sustainable development. Semiconductor photocatalysis has become a feasible method to solve these problems. In this paper, two novel p–n type heterojunctions BiOI(100)@TpPa-1 COFs (B1T_x) and BiOI(001)@TpPa-1 COFs (B0T_x) were successfully synthesized between BiOI with different crystal faces and imine-type TpPa-1 COFs, and the degradation of organic pollutants (TC, MO) and CO₂ reduction were used to evaluate the photocatalytic performance of the B1T_x and B0T_x series heterojunctions. The photocatalytic decomposition of both tetracycline (TC) and methyl orange (MO) could reach more than 90%, while the yield of CO₂ reduction reached 62.52 μmol g⁻¹ h⁻¹. The enhanced photocatalytic performance of BiOI@TpPa-1 COFs resulted mainly from (i) the integration of TpPa-1 COFs, which expanded the light absorption spectrum and enhanced the utilization of the BiOI lamellar structure; (ii) the existence of a built-in electric field in the BiOI@TpPa-1 COF heterojunction verified by density functional theory (DFT) calculations; and (iii) efficient separation and transfer of photogenerated charges accomplished under the combined influence of the heterojunction interfacial electric field and crystal face electric field. This study focuses on the construction of heterojunctions with different crystal faces, which provides a good idea for improving the photocatalytic performance of Bi-based catalysts.