Aggrandized photocatalytic H2O2 and H2 production by a TiO2/Ti3C2-TiC/mixed metal Ce-Zr MOF composite: an interfacial engineered solid-state-mediator-based Z-scheme heterostructure

The development of well-designed all-solid-state Z-scheme hybrid architectures with highly active distinct functional materials has received huge attention due to their great potential for solar-to-fuel energy production. However, delicately constructing a multiphase heterojunction with a high-flux charge shuttle through material design strategies remains a challenge. Herein, we demonstrate a unique protocol involving a bio-inspired multivariate mediator-based Z-scheme TiO2/Ti3C2-TiC and mixed metal Ce/Zr-UiO-66-NH2 (CZUNH) heterostructure (TiO2/Ti3C2-TiC/CZUNH) by an interfacial engineering approach for highly promoted photocatalytic H2O2 and H2 production. The structural analysis of the TiO2/Ti3C2-TiC/CZUNH composite revealed that CZUNH accumulated on the surface of TiO2/Ti3C2-TiC nanosheets, providing dense active sites for enhanced photocatalytic reactions. The HRTEM and XPS characterization distinctly clarified the close interfacial interaction between CZUNH and TiO2/Ti3C2-TiC. Mechanistic investigation showed that the Ti3C2-TiC nanosheets act as a solid-state electron mediator, constructing an electron-shuttling route between CZUNH and TiO2 and thus extending the lifetime of photo-induced charge carriers generated on CZUNH and TiO2, respectively. Specifically, the transfer channel pathway of the Z-scheme-based TiO2/Ti3C2-TiC/CZUNH-20 composite with a tremendous driving force provides an optimum H2O2 production capacity of 1575 mu mol h-1 g-1, which is approximately 3.5- and 2.8-fold higher than those of neat TiO2/Ti3C2-TiC and CZUNH, respectively. Moreover, the optimal visible light H2 evolution rate of 570 mu mol h-1 (with ACE 9.1%) is four and three times higher than those of pristine TiO2/Ti3C2-TiC and CZUNH, respectively. This research provides deep understanding of the design of a highly active mediator-based Z-scheme heterojunction interface for improving the catalytic performance of MXene-derived photocatalysts.