MOF-Derived Multi-heterostructured Composites for Enhanced Photocatalytic Hydrogen Evolution
Deciphering the Roles of Different Components
Mian Zahid Hussain (Technische Universität München, University of Exeter)
Zhuxian Yang (University of Exeter)
Bart Van Der Linden (TU Delft - Applied Sciences)
Werner R. Heinz (Technische Universität München)
Mounib Bahri (University of Strasbourg)
Ovidiu Ersen (University of Strasbourg)
Quanli Jia (Zhengzhou University)
Roland A. Fischer (Technische Universität München)
Yanqiu Zhu (University of Exeter)
Yongde Xia (University of Exeter)
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Abstract
Bimetal-organic-framework (Bi-MOF) NH2-MIL-125(Ti/Cu)-derived nanocomposites are systematically investigated to elucidate the role of individual species TiO2, CuxO and the porous carbon matrix in photocatalytic activity. Among the studied samples, the TiO2/CuxO/C nanocomposite derived from heat processing NH2-MIL-125(Ti/Cu) under Ar/H2O vapor demonstrates the highest photocatalytic H2 evolution performance due to the formation of a phasejunction between the well-crystallized anatase/rutile TiO2 polymorph, the optimized and codoped nitrogen/carbon in the composites, the formation of p-n heterojunctions between the TiO2 and CuxO nanoparticles, as well as their uniform distribution in a hydrophilic porous carbon matrix decorated with N and carboxylic functional groups. These parameters enable the in situ-formed multi-heterostructures in these nanocomposites to not only possess relatively narrower energy band gaps and improved spatial charge separation due to the formed type-II staggered p-n heterojunctions but also offer multiple pathways for charge diffusion, resulting in lower charge-transfer resistance, suppressed bulk charge recombination, and consequently, much improved visible-light absorption. Therefore, the Bi-MOF NH2-MIL-125(Ti/Cu)-derived TiO2/CuxO/C nanocomposite provides easily accessible active sites with an excellent photocatalytic H2 evolution activity of 3147 μmol gcat-1 h-1, 99 times higher than that of bare TiO2. This work provides a simple one-step approach to producing tunable novel nanocomposites for efficient photocatalytic H2 evolution without using expensive noble metals as cocatalysts.
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