Covalent organic framework based WO3@COF/rGO for efficient visible-light-driven H2 evolution by two-step separation mode

Abstract

Covalent organic framework based Z-scheme heterostructure for efficient visible-light-driven hydrogen evolution. • A WO 3 @TpPa-1-COF core–shell Z-scheme heterojunction was firstly reported. • Bulk WO 3 was etched into ultra-small nanostructurer in the synthesis of composite. • WO 3 @TpPa-1-COF/rGO(30%) exhibits a high H 2 evolution rate of 26.73 mmol·g −1 ·h −1 . • The rGO facilitates the separation of charge carriers in the Z-scheme heterojunction. Covalent organic frameworks (COFs) are a new type of visible-light-driven photocatalysts, while effectively improving the separation and transfer of light-induced charges is of the key point to further enhance their activity. In this work, a new COF-based core–shell Z-scheme heterojunction WO 3 @TpPa-1-COF was firstly synthesized by in-situ etching bulk WO 3 into ultra-small nanostructure. Further, a ternary WO 3 @TpPa-1-COF/rGO composite with rGO attached on the surface of TpPa-1-COF was prepared by a facile one-pot photoreduction of GO solution containing as-synthesized WO 3 @TpPa-1-COF. The results of photocatalytic measurements show that the WO 3 @TpPa-1-COF/rGO(30%) composite material possesses a hydrogen evolution rate of 26.73 mmol·g −1 ·h −1 under visible-light irradiation, which is 11.73 and 1.6 times higher than that of TpPa-1-COF and WO 3 @TpPa-1-COF, respectively. Further study demonstrate a Z-Scheme charge transfer pathway exists in WO 3 @TpPa-1-COF/rGO composite which promote the separation of photogenerated charge carriers from COF, while the rGO attached on COF serves as electron collector in photocatalytic process further facilitating the transfer of photogenerated electrons to active sites. The reported strategy of building core–shell COF-base heterostructure and the resulting architecture with rGO as electron collector in Z-Scheme for facilitating the separation and transfer of charge carriers may open a new way for the design of highly efficient photocatalysts.